Water Quality in Inland Ponds for Low-Salinity Culture of Pacific White Shrimp  
Litopenaeus vannamei 
 
by 
 
Naparat Prapaiwong 
 
 
 
 
A dissertation submitted to the Graduate Faculty of 
Auburn University 
in partial fulfillment of the 
requirements for the Degree of 
Doctor of Philosophy 
 
Auburn, Alabama 
December 12, 2011 
 
 
 
 
Keywords: Pacific white shrimp Litopenaeus vannamei, low salinity water,  
water quality, effluent, trace elements, temperature 
 
 
Copyright 2011 by Naparat Prapaiwong 
 
 
Approved by 
 
Claude E. Boyd, Chair, Professor of Fisheries and Allied Aquacultures 
Yolanda J. Brady, Associate Professor of Fisheries and Allied Aquacultures 
John W. Odom, Associate Professor of Agronomy and Soils 
Mark R. Liles, Associate Professor of Biological Sciences 
 
 
 
 
 
 
ii 
 
 
 
 
 
 
 
 
 
Abstract 
 
 
Four investigations were performed in inland, low-salinity shrimp farms in 
Blackland Prairie Region in western Alabama.  Three of these investigations were related 
to performance of shrimp responses to variation of water quality variables in ponds.  The 
forth investigation was performed to address the concern of environmental impacts as a 
result of utilization of saline water for aquaculture purpose in inland region. 
Common water quality variables in nine ponds exhibited wide variation in 
concentration among ponds and overtime.  Shrimp performance varied significantly 
among ponds as follows: survival, 16 to 128%; production, 928 to 5, 950 kg/ha; feed 
conversion ratio, 1.18 to 2.89.  None of the water quality variables were at the lethal 
concentrations but few variables were occasionally outside optimum ranges for shrimp 
production and may have stressed shrimp.  Survival and production were positively 
correlated (P < 0.05) with increasing concentration of methyl orange alkalinity, total 
alkalinity, and calcium hardness.  Production was negatively correlated with higher pH 
and temperature but these correlations may have resulted from lower temperature and pH 
during final days of the crop in ponds harvested in October rather than from actual effect 
of temperature and pH on growth.  Variables that were correlated with shrimp survival 
and growth or outside optimal ranges deserved to be further investigated to ascertain 
whether or not they are causal and harmful. 
iii 
 
 
 
 
Concentrations of 18 trace elements tended to be greater than concentration in 
normal seawater except for molybdenum, boron, and silicon.  Concentrations of most 
trace elements varied greatly among ponds and sampling dates.  The analytical method 
used in this investigation measured total concentrations of trace elements, includes free 
ionic forms, hydrolysis products, ion pairs, and coordination compounds (chelated 
forms), but only the free ionic forms that are toxic to aquatic organisms.  Although 
concentrations of iron, aluminum, zinc, and selenium were occasionally higher than 
typical, safe concentration limits for continuous exposure to aquatic life, it is doubtful 
that free ionic concentrations in these waters were great enough to harm shrimp.  Positive 
correlations (P < 0.05) between shrimp survival and production, and increasing 
concentrations of zinc, cobalt, and iron should be further investigated to ascertain if 
additions of these elements to ponds might improve shrimp performance. 
Monthly, mean water temperature among eight ponds differed by 3.40oC in May 
and 2.83 oC in September, but there was less than 1 oC difference among pond in June, 
July, and August.  Differences in water temperature among ponds were not related to 
pond water surface:volume ratio.  The differences in water temperature among ponds 
probably were related mainly to variation in plankton density.  The negative correlations 
(P < 0.05) between water temperature and shrimp production and survival are thought to 
have resulted from variation in crop duration and therefore are not causal.  However, 
differences in water temperature among ponds in May and September were great enough 
to have possibly influenced shrimp survival and production. 
Investigations of effluent volume and pollutant loads of an inland, low-salinity 
shrimp farm were conducted in 2008 and 2010 and the draining effluent at harvest of 
iv 
 
 
 
 
both years were 50.4% and 57.9 % of impounded water, respectively.  Farm effluent 
caused a notable increase in concentrations of all variables other than pH at sampling 
station downsteam of the farm outfall.  But only chloride concentration exceeded 230 
mg/Luni2500 upper standard for freshwater streams set by the Alabama Department of 
Environmental Management.  Average pollutant discharge per tonne of shrimp was 444.9 
kg total suspended solids, 51.3 kg 5-d biochemical oxygen demand, 15.2 kg total 
nitrogen, 1.33 kg total phosphorus, and 4,402 kg chloride.  Concentrations of turbidity, 
settleable solids, total suspended solids, total phosphorus and possibly other variables in 
effluent could be lessened by installation of a settling basin to remove medium and coarse 
solids before final discharge.  Release of less water from the farm during harvest, and 
improvement in feed conversion ratio also would lessen pollutant loads per tonne of 
shrimp. 
 
 
 
 
 
 
 
 
 
 
 
v 
 
 
 
 
 
 
 
 
 
Acknowledgements 
 
 
The author would like to express her deepest gratitude to Dr. Claude E. Boyd for 
theopportunities he has offered, guidance, and assistance throughout her studies.  The 
author would also like to extend appreciation to her committee members (Dr. Yolanda J. 
Brady, Dr. John W. Odom, and Dr. Mark R. Liles) and her dissertation outside reader 
(Dr. Philip L. Chaney, Department of Geology and Geography) for their time, advice, and 
helpful discussions.  The author extends her gratitude to Dr. David R. Teichert-
Coddington and Dr. Rudy H. Schmittou for providing data and their assistance.  The 
author would like to further thank to her colleagues in Dr. Boyd?s lab for their assistance 
collecting field data. Most importantly she thanks her mother, Somboon Prapaiwong, and 
her sisters and brothers, for their unconditional supports. 
 
 
 
 
 
 
 
 
 
 
vi 
 
 
 
 
 
 
 
 
 
Table of Contents 
 
 
Abstract ............................................................................................................................... ii 
Acknowledgements ............................................................................................................. v 
List of Tables ...................................................................................................................viii 
List of Figures ..................................................................................................................... x 
I.     Introduction ................................................................................................................. 1 
II.    Literature Review ........................................................................................................ 3 
III.  Effects of Major Water Quality Variables on Shrimp Production in Inland, Low-  
Salinity Ponds in Alabama ........................................................................................ 18 
 
Abstract ................................................................................................................. 18 
Introduction ........................................................................................................... 19 
Materials and Methods .......................................................................................... 19 
Results and Discussion ......................................................................................... 21 
Literature Cited ..................................................................................................... 34 
IV.  Trace Elements in Waters of Inland, Low-Salinity Shrimp Ponds in Alabama ........ 50 
Abstract ................................................................................................................. 50 
Introduction ........................................................................................................... 51 
Materials and Methods .......................................................................................... 52 
Results and Discussion ......................................................................................... 54 
Literature Cited ..................................................................................................... 59 
 
vii 
 
 
 
 
V.  Water Temperature in Inland, Low-Salinity Shrimp Ponds in Alabama .................... 68 
Abstract ................................................................................................................. 68 
Introduction ........................................................................................................... 69 
Materials and Methods .......................................................................................... 70 
Results and Discussion ......................................................................................... 71 
Literature Cited ..................................................................................................... 75 
VI.  Effluent Volume and Pollutant Loads at an Inland, Low-Salinity Shrimp Farm         
in Alabama................................................................................................................. 86 
 
Abstract ................................................................................................................. 86 
Introduction ........................................................................................................... 88 
Materials and Methods .......................................................................................... 89 
Results ................................................................................................................... 93 
Discussion ............................................................................................................. 94 
Literature Cited ..................................................................................................... 98 
 
 
 
 
 
 
 
 
 
 
viii 
 
 
 
 
 
 
 
 
 
List of Tables 
 
 
III. Table 1.  Pond Information and Data on Stocking, Aeration, and Feed Application    
in Nine Ponds on an Inland, Low-Salinity Shrimp Farm in Alabama ......... 38 
 
III. Table 2.  Grand Means and Standard Deviations for Water Quality Variables      
Measured at 2-wk Intervals for Nine Ponds on and Inland, Low-Salinity 
Shrimp Farm in Alabama. Correlation Coefficients (r) between Total          
Feed Input and Water Quality Variables also are Given ............................. 39 
 
III. Table 3.  Harvest Data and Production Performance in Nine Ponds on an Inland,      
Low-Salinity Shrimp Farm in Alabama ....................................................... 40 
 
III. Table 4.  Correlation Coefficients among Water Quality Variables and Shrimp     
Survival and Production in Nine Ponds at an Inland, Low-Salinity      
Shrimp Farm in Alabama ............................................................................. 41 
 
IV. Table 1.  Data on Pond Area and Depth, Stocking Date and Postlarval (PL)        
Density, Aeration Rate, and Amount Feed Applied for Seven Ponds               
at Farm A, an Inland, Low-Salinity Shrimp Farm in Alabama ................... 62 
 
IV. Table 2.  Dry Weight Concentrations of Trace Elements in shrimp and Feed,       
Grand Means, Standard Deviations (SD), Ranges and Coefficients of 
Variation (CV) for Trace Element Concentrations for Waters of Ten      
Ponds at Inland, Low-Salinity Shrimp Farms in Alabama. Correlation 
Coefficients (r) between Feed Inputs of Trace Elements (X variable)        
and Concentrations of these Elements in Waters of Seven Ponds on         
One Farm also are Shown ............................................................................ 63 
 
IV. Table 3.  Summary of Safe Concentrations of Trace Elements to Aquatic Life          
for Long-Term Exposure. Developed from Data Presented by Australian  
and New Zealand Council on Environmental Protection (1992), Boyd      
and Tucker (1998), and United States Environmental Protection Agency 
(1976) ........................................................................................................... 64 
 
IV. Table 4.  Harvest Data, Crop Duration, Survival, Production, and Feed Conversion     
Ratio (FCR) for Seven Ponds at Farm A, an Inland, Low-Salinity Shrimp     
Farm in Alabama.......................................................................................... 65 
 
ix 
 
 
 
 
IV. Table 5.  Correlation Coefficients between Trace Element Concentrations in        
Water (X Variable) and Shrimp Survival, Production, and Feed     
Conversion Ratio (FCR) in Inland Shrimp Ponds in Alabama.           
Asterisks by Entries Denote Significance at P < 0.05 ................................. 66 
 
V. Table 1.   Pond Areas and Depths, Stocking Dates, Aeration Rates, and Amounts        
of Feed Applied to Eight Study Ponds at an Inland, Low-Salinity         
Shrimp Farm in Alabama ............................................................................. 77 
 
V. Table 2.   Production, Crop Duration, Survival Rates, and Feed Conversion Ratio 
(FCR) for Eight Ponds at an Inland, Low-Salinity Shrimp Farm                   
in Alabama ................................................................................................... 78 
 
V. Table 3.   Monthly, Average Water Temperature for Eight Ponds at an Inland, Low-
Salinity Shrimp Farm in Alabama. The Letter H Designated that Ponds  
were Harvested in September and could not be Used in the Average ......... 79 
 
VI. Table 1.  Weighted Means (g1876g1191) ? Standard Errors (SE) for Concentrations of    
Selected Water Quality Variables in Draining Effluent from Four         
Ponds on an Inland, Low-Salinity Shrimp Farm in Alabama in 2008         
and 2010 ......................................................................................................101 
 
VI. Table 2.  Total Qualities of Selected Pollutants Discharged and the Amount of       
each Pollutant per Tonne of Shrimp Production in 2008 and 2010                
at an Inland, Low-Salinity Shrimp Farm in Alabama .................................102 
 
VI. Table 3.  Concentrations of Water Quality Variables in a Creek Upstream of             
an Inland, Low-Salinity Shrimp Farm Contrasted with Downstream  
Concentrations of the Variables during Draining of Ponds for Harvest         
in 2008 ........................................................................................................103 
 
 
 
 
 
 
 
 
x 
 
 
 
 
 
 
 
 
 
List of Figures 
 
 
III. Fig. 1.  Distribution of Concentrations of Total Ammonia Nitrogen and Total 
Hardness Measured in Nine Ponds at 2-Wk Intervals at an Inland, Low-
Salinity Shrimp Farm in Alabama .................................................................. 42 
 
III. Fig. 2.  Farm Means (all Ponds Averaged by Date) and Standard Deviations for 
Conductivity, Water Temperature, pH, Dissolved Oxygen, and Carbon 
Dioxide in Nine Ponds at an Inland, Low-Salinity Shrimp Farm                       
in Alabama ...................................................................................................... 43 
 
III. Fig. 3.  Correlations between Conductivity and Salinity and Total Dissolved        
Solids in Waters of Ponds at an Inland, Low Salinity Shrimp Farm                 
in Alabama ...................................................................................................... 44 
 
III. Fig. 4.  Farm Means (all Ponds Averaged by Date) and Standard Deviations              
for Total Alkalinity and Methyl Orange Alkalinity and Total Hardness        
and Calcium Hardness in Nine Ponds at an Inland, Low-Salinity            
Shrimp Farm in Alabama ................................................................................ 45 
 
III. Fig. 5.  Farm Means (all Ponds Averaged by Date) and Standard Deviations             
for Hydrogen Sulfide, Nitrite-Nitrogen, Total Ammonia Nitrogen,          
Nitrate-Nitrogen, Total Nitrogen, and Total Phosphorus in Nine Ponds           
at an Inland, Low Salinity Shrimp Farm in Alabama ..................................... 46 
 
III. Fig. 6.  Farm Means (all Ponds Averaged by Date)  and Standard Deviations            
for Secchi Disk Visibility, Turbidity, and Chlorophyll a in Waters of          
Nine Ponds on an Inland, Low Salinity Shrimp Farm in Alabama ................ 47 
 
III. Fig. 7.  Regression Lines and Correlation Coefficients (r) for Relationships         
among Secchi Disk Visibility, Turbidity, and Chlorophyll a Data        
Collected from Nine Ponds over the Grow-Out Season at an Inland,          
Low-Salinity Shrimp Farm in Alabama .......................................................... 48 
 
III. Fig. 8.  Correlation between Survival and Crop Duration and Production of        
Shrimp at an Inland, Low-Salinity Shrimp Farm in Alabama ........................ 49 
 
IV. Fig. 1.  Variation in Concentrations of Eight Trace Elements; Cobalt,      
Molybdenum, Boron, Iron, Nickel, Lead, Copper, and Zinc on each    
Sampling Date for Pond N-8 at Farm A ......................................................... 67 
xi 
 
 
 
 
V. Fig. 1.   Daily Minimum and Maximum Water Temperature in Pond N-7                     
at an Inland, Low-Salinity Shrimp Farm in Alabama ..................................... 80 
 
V. Fig. 2.   Mean Daily, Air Temperatures and Water Temperatures in Pond N-7              
at an Inland, Low-Salinity Shrimp Farm in Alabama ..................................... 81 
 
V. Fig. 3.   Left: Relationship between Average, Daily Air Temperatures and              
Water Temperatures in Pond N-7 at an Inland, Low-Salinity Shrimp         
Farm in Alabama. Right: Relationship between Average, Daily Water 
Temperatures Averaged by Two Methods: Average of 2-H Reading             
and Minimum-Maximum Temperature Averaging ........................................ 82 
 
V. Fig. 4.   Relationship between Aeration Rate and Pond Surface Area/Volume          
Ratio to Average, and Average, Crop-Period Water Temperatures in         
Eight Ponds at an Inland, Low-Salinity Shrimp Farm in Alabama ................ 83 
 
V. Fig. 5.   Relationships between Average, Crop-Period Water Temperature and     
Shrimp Production Variables in Eight Ponds at an Inland, Low-Salinity 
Shrimp Farm in Alabama ................................................................................ 84 
 
V. Fig. 6.   Relationship of Crop Duration to Average, Crop-Period Temperature              
in Eight Ponds at an Inland, Low-Salinity Shrimp Farm in Alabama ............ 85 
 
VI. Fig. 1.  Map of the Inland, Low-Salinity Shrimp Farm in Alabama where                 
the Study was Conducted ...............................................................................104 
 
VI. Fig. 2.  Mean Concentrations and Standard Deviations for Water Quality        
Variables Measured at Different Stages of Pond Water Level Drawdown      
for Harvest at an Inland, Low-Salinity Shrimp Farm in Alabama .................105 
 
1 
 
 
 
 
 
 
 
 
 
I.  Introduction 
 
 
The shrimp aquaculture industry has experienced remarkable growth in the past 
two decades.  Products from shrimp aquaculture account for more than 40 % of world 
shrimp production.  The global shrimp production from aquaculture has increased from 
700,000 metric tonnes in 1997 to about 4.6 million tonnes in 2006 (Food and Agriculture 
Organization of the United Nations 2009) .  In the past, two major marine shrimp species 
were commercially cultured in two different hemispheres uni2500 the black tiger shrimp 
Penaeus monodon and the Pacific white shrimp Litopenaeus vannamei were cultured in 
the eastern and western hemispheres of the globe, respectively.  However, the two species 
from the two different hemispheres had at least one thing in common, they were 
cultivated in brackish or seawater of 15 to 30 ppt salinity in ponds situated in near-coastal 
areas.  The culture of marine shrimp in low-salinity water in inland areas has become 
common in many regions of the world including: Australia, China, Ecuador, India, 
Thailand, the United States, and other countries (Boyd and Thunjai 2003).  The most 
common marine shrimp species that has been cultivated in low-salinity water throughout 
the world has been L. vannamei.  In Thailand, low-salinity cultivation of marine shrimp 
often is performed by transporting hyper-saline water at salinity of 80 to 200 ppt or 
sometime even more from coastal seawater evaporation ponds to inland ponds and 
mixing with freshwater in ponds to obtain the desirable salinity of 0.5 to 5 ppt (Boyd et 
al. 2002, Limsuwan et al. 2002).  In the United States, culture of marine shrimp in inland 
2 
 
 
 
 
area has become popular, and currently, it is conducted in several states including 
Alabama, Arizona, Arkansas, Florida, Illinois, Indiana, and Texas (Samocha et al. 1998, 
Samocha et al. 2002, Saoud et al. 2003).  In Alabama, the inland cultivation of Pacific 
white shrimp is possible through use of the ancient saltwater deposited in underground 
aquifers in the Blackland Prairie region.  The commercial, inland cultivation of Pacific 
white shrimp in Alabama started about a decade ago in the west-central region of the 
state.  With four active producers and a culture area of more than 30 ha, these farms 
produce around 135,000 kg shrimp production each year with a total farm gate value of 
more than 1 million US dollars (Whitis 2007).  
In the past decade, much progress has been made in inland, low-salinity culture of 
marine shrimp in Alabama.  However, further research is still necessary to increase its 
potential and achievement.  Comprehension of the influence of each particular water 
quality variable, chemical and physical, on the performance of shrimp is key to success in 
shrimp culture.  In addition, there is a growing global concern of the possible negative 
environmental consequences of aquaculture on the surrounding environment.  Thus, 
further studies on water quality in ponds at inland shrimp farms are needed both for 
improving production and for protecting environment.  The Blackland Prairie region of 
Alabama is economically depressed, and any information that will encourage the 
expansion and profitability of inland shrimp farming in that region would be highly 
beneficial. 
 
 
 
 
 
3 
 
 
 
 
 
 
 
 
 
II.  Literature Review 
 
 
Water sources for inland, low-salinity shrimp culture 
In some countries, for example Thailand, the source of briny water for inland, 
low-salinity cultivation of shrimp is mainly seawater evaporation ponds (Boyd et al. 
2002, Limsuwan et al. 2002).  This water typically has salinity of 80 to 200 ppt, and in 
some cases even more.  High-salinity water is trucked to the inland culture sites and 
mixed with freshwater in ponds to obtain desirable salinities.  In several other countries, 
the primarily source of saline water for inland, low-salinity marine shrimp culture is 
groundwater from saline aquifers (Boyd and Thunjai 2003).  Saline groundwater used for 
filling inland, low-salinity shrimp pond in Alabama has salinity of about 2 to 10 ppt.  
Water from underground aquifer from the Blackland Prairie region in Alabama is lower 
in magnesium and potassium levels in comparison to seawater of the same strength 
(Boyd and Thunjai 2003).  Potassium and magnesium have been reported to be necessary 
for shrimp, because they play particular roles in physiological processes (Boyd and 
Thunjai 2003).  There is evidence that low concentrations of potassium and magnesium 
in culture water of shrimp in inland, low-salinity ponds in Alabama lessen performances 
of Pacific white shrimp (Roy et al. 2010).  The ion deficiency problem is mitigated by 
applying potassium and magnesium fertilizers; muriate of potash (potassium chloride), 
and Kmag (potassium magnesium sulfate) to elevate concentrations to 40 mg/L and 20 
mg/L, respectively (McNevin et al. 2004). 
4 
 
 
 
 
In Alabama, the supplies of water from drilled wells are not adequate to allow 
water exchange when a farmer feels that one or more water quality variables are out of 
range as have been practiced in shrimp aquaculture in near-coastal areas.  In contrast to 
shrimp aquaculture in other parts of the world, inland shrimp producers in Alabama store 
as much water as possible in their ponds for the next crop. 
 
Pacific white shrimp and water quality variables 
Pacific white shrimp Litopenaeus vannamei is a marine species that can tolerate 
wide range of salinities from 0 to 45 ppt (Araneda et al. 2008, Bray et al. 1994, McGraw 
and Scarpa 2002, Menz and Blake 1980).  However, the best success in cultivation of this 
species has been documented in waters 0.5 to 28.3 ppt salinity (Samocha et al. 1998).  
This species can grow and survive at low-salinity as long as there are sufficient 
concentrations of major ions (McGraw and Scarpa 2002).  Pacific white shrimp widely 
cultured for more than a decade in several countries in Asia and the America as well as 
Australia.  In Alabama, L. vannamei has been cultured in inland, low-salinity ponds since 
1999 (Whitis 2007). 
Both intrinsic and extrinsic factors play roles in biological activities of many 
crustacean species (Achituv and Cook 1984, Emmerson 1985, Hagerman and 
Weber1981, Schmidt-Nielsen 1983, Spanopoulos-Hernandez et al. 2005).  With the 
exception of organically bound elements carbon, hydrogen, nitrogen, and oxygen, there 
are several other elements that are considered to be essential for animal life uni2500 the 
macroelements and microelements.  The macroelements include; the cationic group uni2500 
calcium, magnesium, potassium, and sodium; and the anionic group uni2500 phosphorus, 
5 
 
 
 
 
chlorine, and sulfur.  The trace or microelements include; cobalt, chromium, copper, 
fluorine, iodine, iron, manganese, molybdenum, nickel, selenium, silicon, tin, zinc, and 
vanadium (Food and Agriculture Organization of the United Nations 1987). 
Macro and microelements have several significant-biological functions in living 
organisms, for instances serving as constituents of skeletal and soft tissue structures, 
necessary for transmission of nerve impulses and muscle contraction,  maintenance of 
osmotic pressure, roles in the regulation of pH of blood and other fluids in body, and are 
vital for function of many enzymes, hormones, vitamins, and respiratory pigments.  For 
example, they serve as cofactors in metabolism, catalysts, and enzyme activators (Food 
and Agriculture Organization of the United Nations 1987). 
Magnesium serves as a cofactor for several enzymes important for the metabolism 
of proteins, carbohydrates, and lipids (Davis and Gatlin 1996).  Magnesium is necessary 
for forming specific enzyme complexes that necessary for osmotic and ionic regulation in 
acclimation of shrimp to lower salinity water.  Magnesium is also necessary for 
neuromuscular transmission and skeletal tissue metabolism (Cheng et al. 2005).  In water 
with an imbalance of ions, shrimp are stressed (Auburn University and USDA-Natural 
Resources Conservation Service).  In inland, low-salinity culture systems, water often 
contains a lower concentration of some ions than would be expected in full strength 
seawater diluted to the same salinity.  In Alabama, low concentrations of magnesium and 
potassium in culture water affect shrimp growth performance.  Stress and mortality of L. 
vannamei is reduced when the potassium ion concentration increases from 2 mg/L to 25 
mg/L (Castillo-Soriano et al. 2010).  Concentrations of magnesium and potassium in 
natural saline groundwater in west Alabama are, approximately, 4.6 mg/L and 6.2 mg/L, 
6 
 
 
 
 
respectively (McNevin et al. 2004).  These concentrations are not sufficient for shrimp 
and addition of these ions is needed.  To mitigate the problem, producers add magnesium 
and potassium to ponds through fertilizers to provide concentrations to about 20 mg/L 
and 40 mg/L, respectively.  Addition of fertilizers resulted in significantly increases in 
production and survival rate (McNevin et al. 2004). 
Solubility of most metals in water is decreased as pH and salinity increase (Boyd 
2000).  Water alkalinity in pond is typically influenced by pond soil and can be predicted 
from soil pH (Boyd and Munsiri 1997).  Inland shrimp farms in Alabama are located in 
an area where soil contains free carbonate (Hajek et al. 1975) and, as a result, pond 
waters have moderate to high alkalinity and pH level of about 7.5 to 8. 
Phytoplankton are the base of the food web, responsible for primary productivity 
in natural water bodies (Wetzel 2001).  One simple approach used for assessing primary 
productivity in water is measuring chlorophyll a concentration.  Phytoplankton 
productivity is usually limited by phosphates in water and availability of phosphorus in 
pond water is usually limited by rapid uptake of this nutrient by pond bottom soils (Boyd 
and Munsiri 1996).  High concentrations of chlorophyll a have been observed in zero-
water exchange, intensive culture of P. vannamei and chlorophyll a values were 
negatively correlated with calcium and zinc concentrations (Castillo-Soriano et al. 2010).  
Trace elements also are essential factors for growth of phytoplankton.  There are several 
studies that report trace element limitations of phytoplankton productivity in some 
freshwater lakes (see review by Wetzel 2001).  For example, phytoplankton 
photosynthesis increased following addition of trace element into high elevation lakes in 
California (Goldman and Wetzel 1963).  Different trace elements play different roles in 
7 
 
 
 
 
phytoplankton physiology.  Molybdenum will be used as an example to show the 
importance of trace elements.  This trace element plays significant roles in the formation 
of nitrate reductase enzyme and in nitrogen fixation.  Molybdenum is essential for the 
growth of higher plants and has been demonstrated to be essential for Chlorella and 
Scenedesmus; it is assumed to be essential for other algae.  Some inland waters have low 
levels of molybdenum and, as a result, limits their productivity (Goldman 1960). 
Water salinity plays significant roles in osmotic and ionic regulations of marine 
shrimp and other marine-aquatic animals.  Litopenaeus vannamei has the strong ability to 
regulate osmotic strength in different saline media.  Litopenaeus vannamei juveniles cope 
with wide variations of water salinity (Wickins 1976) by regulating ion concentrations in 
their haemolymph in respond to external salinity variations.  To obtain the maximum 
production in culturing L. vannamei, a shrimp farm needs to maintain cultured water to 
the optimum salinity.  This species hyper-regulates between salinities of 10 and 20 ppt 
and hypo-regulates between 20 to 40 ppt (Buckle et al. 2006).  Alvarez et al. (2004) 
reported that activity of the Na+/K+-ATPase enzyme is higher at low salinities.  Smaller 
shrimp suffered osmotic stress and consumed more oxygen at high salinity.  In contrast, 
larger shrimp suffered much stress at low salinity (Bett and Vinatea 2009).  Acclimation 
and salinity of water during stocking of Pacific white shrimp postlarvae is positively 
correlated to the survival and growth of post larvae (Alvarez et al. 2004, Saoud et al. 
2003) but not survival rate during growout (Alvarez et al. 2004).  Atwood et al. (2003) 
and Sowers et al. (2005) reported that Pacific white shrimp did not grow as efficiently in 
seawater diluted with freshwater supplemented with a salt mixture as in regular seawater, 
but osmotic dysfunction was not detected.  Sowers et al. (2006) reported higher growth of 
8 
 
 
 
 
this species in low-salinity water of 2 ppt than in seawater.  However, the influence of 
water salinity on shrimp growth is not well documented (Bett and Vinatea 2009, Bray et 
al. 1994, Samocha et al. 1998). 
Dissolved oxygen (DO) is one of the most important factors in aquaculture ponds, 
especially in semi-intensive and intensive culture systems, because it is essential in 
respiration, and its availability determines the capacity of aquaculture ponds (Boyd 
1990).  A DO concentration of 5 mg/L or more is the ideal level for aquatic life.  
However, the exact concentration of dissolved oxygen varied from pond to pond because 
of variations of chemical, biological, and ecological characteristics.  Dissolved oxygen 
consumption rate of P. vannamei is influenced by interaction of temperature, salinity, and 
shrimp size.  Oxygen consumption of P. vannamei is higher when water salinity is below 
25 ppt at a temperature lower than 20oC, while oxygen consumption seems to be more 
stable at lower salinities uni2500 15 to 25 ppt and at temperature of 25 to 30oC (Bett and 
Vinatea 2009).  McGraw et al. (2001) reported increasing yield of P. vannamei and P. 
stylirotris when minimum dissolved oxygen in water increased from 15% to 65% of 
saturation. 
Ammonia is the main nitrogenous excretory product of most aquatic animals 
including crustaceans (Forster and Goldstein 1969) and it is the product of the 
ammonification of organic matter in culture systems (Chen et al. 1990).  Ammonia is 
highly toxic to marine species (Armstrong et al. 1978).  Un-ionized ammonia is highly 
lipid soluble with the capability to diffuse across the cell membrane (Chen and Kou 
1993) and can be detrimental to shrimp at high concentrations. Ammonia exists in 
solution primarily as ionized ammonium (NH4+) ion and un-ionized ammonia (NH3) 
9 
 
 
 
 
molecule.  The proportion of ionized and un-ionized ammonia is highly pH-dependent 
(Armstrong et al. 1978). 
Temperature is one of the most important and most changeable physical factors 
affecting living organisms.  Temperature can affect reproductive systems, growth and 
development, morphological systems, and the respiratory system.  Respiration of L. 
stylirostris (Spanopoulos-Hernandez et al. 2005) and P. chinensis (Chen and Nan 1993) 
increase with increasing water temperature.  Lower water temperature seems to reduce 
the hyperosmoregulatory ability of juvenile Pacific white shrimp (Bett and Vinatea 
2009). 
 
Effluents from shrimp culture and environment 
Human activities often have negative environmental impacts and aquaculture is 
no exception.  The rapid development of inland shrimp farming has led to concerns over 
sustainability of resources and potential, negative environment impacts associated with 
the activity.  The major concerns are over salination and nutrient pollution of natural 
waters, and soil salination resulting from farm effluents.  Effluents from shrimp 
aquaculture activities released during harvest could possibly deteriorate their adjacent 
environment.  Excess nutrient and waste loads released to estuaries may possibly lead to 
eutrophication and harmful algal blooms, excess toxic chemicals and other toxins, 
changes in community structure and biodiversity, and introducing diseases and exotic 
materials into receiving water.  However, the severity of impacts due to effluents from 
shrimp aquaculture differs from place to place and from time to time, and they can be 
minimized or prevented through use of good management practices. 
10 
 
 
 
 
Small to moderate amounts of water from inland shrimp ponds in west Alabama 
can be lost to its environment through seepage and overflow during or after raining as 
well as through drainage during harvest (Boyd et al. 2006).  The effluents have potential 
to salinate freshwater streams to concentrations that are greater than recommended by the 
United States Environmental Protection Agency (Benoit 1988).  Seepage from ponds also 
can salinate shallow, freshwater aquifers near farms (Boyd et al. 2006). 
In inland, low-salinity culture of Pacific white shrimp in west Alabama, producers 
try to conserve water as much as possible for the next growout year, nevertheless part of 
water is released to adjacent freshwater streams.  Boyd et al. (2006) reported that the 
majority of salts input into ponds of these shrimp farms was loss to receiving water 
through discharged water, whereas a small percentage of the salt input remained in pond 
water or was adsorbed by pond bottom soils.  The salts discharged in effluents resulted in 
increasing salinity of the receiving water (Boyd et al. 2006, Pine and Boyd 2010).  
Likewise, inland shrimp farms in Thailand lose the majority of salts to their environment 
through seepage and harvest effluent (Braaten and Flaherty 2001). 
In the United States, an aquaculture facility is classified as a concentrated aquatic 
animal production (CAAP) facility if it is discharging 30 days or more annually and 
producing more than 45,455 harvest weight kilograms annually.  A CAAP facility is 
subjected to the United States Environmental Protection Agency (USEPA) aquaculture 
effluent rule (Federal Register 2004) and is requires a National Pollutant Discharge 
Elimination System (NPDES) permit. 
 
 
11 
 
 
 
 
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shrimp Litopenaeus vannamei at different temperatures and salinities, and optimal 
culture environment. Revista de Biologia Tropical (International Journal of 
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McGraw, W. J. and J. Scarpa. 2002. Determining ion concentrations for Litopenaeus 
vannamei culture in freshwater. Global Aquaculture Advocate 5: 36-38. 
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Boone. Journal of Experimental Marine Biology and Ecology 48: 99-111. 
16 
 
 
 
 
Pine, H. J. and C. E. Boyd. 2010. Adsorption of magnesium by bottom soils in inland 
brackishwater shrimp ponds in Alabama. Journal of the World Aquaculture 
Society 41: 603-609. 
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Shrimp culture in inland low salinity waters. Reviews in Aquaculture 2: 191-208. 
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juvenile Penaeus vannamei in low salinity water in a semi-closed recirculating 
system. Israeli Journal of Aquaculture 50: 55-59. 
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Lawrence, and P. Van Wyk. 2002. Review of some recent developments in 
sustainable shrimp farming practices in Texas, Arizona, and Florida. Journal of 
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Saoud, I. P., D. A. Davis, and D. B. Rouse. 2003. Suitability studies of inland well 
waters for Litopenaeus vannamei culture. Aquaculture 217: 373-383. 
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University Press, Cambridge. 
Sowers, A. D., D. M. Gatlin, S. P. Young, J. J. Isley, C. L. Browdy, and J. R. 
Tomasso 2005. Responses of Litopenaeus vannamei (Boone) in water containing 
low concentrations of total dissolved solids. Aquaculture Research 36: 819-823. 
Sowers, A. D., J. R. Tomasso, C. L. Browdy, and H. L. Atwood. 2006. Production 
characteristics of Litopenaeus vannamei in low-salinity water augmented with 
mixed salts. Journal of the World Aquaculture Society 37: 214-217. 
17 
 
 
 
 
Spanopoulos-Hernandez, M., C. A. Martinez-Palacios, R. C. Vanegas-Pe?rez, C. 
Rosas, and L. G. Ross. 2005. The combined effects of salinity and temperature 
on the oxygen consumption of juvenile shrimps Litopenaeus stylirostris 
(Stimpson, 1874). Aquaculture 244: 341-348. 
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http://www.encyclopediaofalabama.org/face/Article.jsp?id=h-1302, Last updated 
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capacity of the shrimp Litopenaeus vannamei at different temperatures and 
salinities, and optimal culture environment. Revista de Biologia Tropical 
(International Journal of Tropical) 54: 745-753. 
 
 
 
 
 
 
 
 
 
 
18 
 
 
 
 
 
 
 
 
 
III. Effects of Major Water Quality Variables on Shrimp Production in Inland, Low-
Salinity Ponds in Alabama 
 
Abstract 
 
 
Common water quality variables in nine inland, low-salinity shrimp ponds in 
Alabama exhibited wide variation in concentrations among ponds and over time.  Shrimp 
performance also varied considerably among ponds in 2008 as follows:  survival, 16 to 
128%; production, 928 to 5,950 kg/ha; feed conversion ratio (FCR), 1.18 to 2.89.  None 
of the measured water quality variables were at concentrations high enough to be lethal to 
shrimp, but a few variables such as, water temperature, dissolved oxygen, carbon dioxide, 
total ammonia nitrogen, calcium, and magnesium were occasionally outside optimum 
ranges for shrimp production and may have stressed shrimp.  Survival and production 
were positively correlated (P < 0.05) with increasing concentrations of methyl orange 
alkalinity, total alkalinity, and calcium hardness.  Negative correlations between 
production and higher pH and water temperature may have resulted from lower water 
temperature and pH during final days of the crop in ponds harvested in October rather 
than from an actual effect of temperature and pH on growth.  Nevertheless, those 
variables that were outside optimal ranges or correlated with shrimp survival or growth 
should be further investigated to ascertain whether or not excursions outside optimum 
ranges are harmful and to determine if observed correlations are causal. 
19 
 
 
 
 
Introduction 
 
 
Low concentrations of potassium and magnesium in saline, groundwater used in 
inland, low-salinity shrimp ponds in Alabama lessen survival and production of the 
culture species L. vannamei (Roy et al. 2010).  Potassium and magnesium fertilizer 
applications are used to counteract this problem (McNevin et al. 2004, Boyd et al. 2007), 
but producers still complain of high variation among ponds in shrimp survival and 
production.  For example, in 17 ponds on one farm, the manager reported that survival 
ranged from 11.9 to 114.6% and harvest yields were 1,110 to 7,247 kg/ha in 2007.  Some 
of these variationswere attributed to inaccuracy in counting postlarvae at stocking and 
from differential survival of newly-stocked postlarvae resulting from acclimation and 
handling.  However, because few disease problems were noted during grow-out, all 
ponds were heavily aerated, and potassium and magnesium concentrations were 
augmented, the manager feels strongly that imbalances in water quality variables other 
than low concentrations of potassium, magnesium, or dissolved oxygen negatively 
affected shrimp performance in some ponds. 
An investigation of the influence of a wide range of water quality variables on 
shrimp production in ponds on this farm was initiated.  This report concerned the 
influence of major water quality variables on shrimp production. 
 
Materials and Methods 
 
 
The shrimp farm is located in the Blackland Prairie region of Alabama about 5 km 
north of Forkland on state Highway 43 in southeastern Greene County.  There are 17 
20 
 
 
 
 
ponds of which nine were selected for the study.  These ponds were chosen because the 
manager had observed problems with low survival, slow growth, or both during the 
previous crop.  Ponds were stocked between 23 April and 7 June 2008 with about 16 to 
30 postlarvae/m2 (Table 1).  A pelleted, 35% crude protein-content feed was offered to 
shrimp twice daily, and mechanical aeration was applied at 8.5 to 13.0 hp/ha mostly at 
night.  Ponds were harvested in September and October 2008, and data on feed use and 
shrimp production were obtained from the farm manager. 
Water quality was monitored at 2-wk intervals.  Because of the 3-h driving time 
to reach the farm, samples and measurements were taken between 1000 and 1400 h.  
Water temperature, dissolved oxygen concentration, pH, conductivity, total dissolved 
solids, and salinity were measured in situ (surface and 10 cm above bottom) using a YSI 
556 MPS Multiprobe system (Yellow Springs Instrument Company, Yellow Springs, 
Ohio, USA), and Secchi disk visibility was determined.   
In each pond, a water sample from approximately 10 cm above the bottom was 
collected from a pier in water of 1.0 to 1.25m deep by aid of a bottom-water sampling 
bottle described by Boyd and Tucker (1992).  Bottom water samples and samples of 
surface water from each pond were immediately analyzed for carbon dioxide and 
hydrogen sulfide using a Hach Model CA-23 Carbon Dioxide Test Kit and a Hach Model 
HS-WR Hydrogen Sulfide Test Kit (Hach Company, Loveland, Colorado, USA). 
Another water sample was collected from a depth of 0.5 m in each pond, put into 
a 2-L plastic bottle, placed on ice in an insulated chest, and transported to Auburn 
University for analyses.  Methods described by Eaton et al. (2005) were used for 
chlorophyll a (membrane filtration, acetone extraction, and spectroscopy), calcium, 
21 
 
 
 
 
magnesium and total hardness (versenate titration), phenolphthalein, methyl orange, and 
total alkalinity (acidimetry), nitrite (diazotization procedure), and turbidity 
(nephelometry).  Total ammonia nitrogen was determined by the salicylate method 
(Bower and Holm-Hansen 1980), and nitrate was measured by the szechrome NAS 
reagent method (Van Rijn 1993).  Aliquots of water samples were digested in alkaline 
persulfate solution as described by Eaton et al. (2005).  This digestion converted all 
phosphorus and nitrogen in the unfiltered samples to phosphate and nitrate, respectively.  
Phosphate concentrations in digestates were measured by the ascorbic acid procedure 
(Eaton et al. 2005), and nitrate was determined by the ultraviolet spectrophotometric 
screening method (Eaton et al. 2005, Gross et al.1999) to provide concentrations of total 
phosphorus and total nitrogen. 
Averages and standard deviations for water quality data were calculated as 
follows:  (1) each pond across all sampling dates (pond means); (2) all ponds for each 
sampling date (farm means); (3) all ponds and all sampling dates (grand means).  The 
relationships between feed inputs to ponds (X variables) and pond means for water 
quality variables and between pond means for water quality variables (X variables) and 
shrimp survival and production were analyzed by regression using SigmaPlot statistical 
software version 10.0 (Aspire Software International, Ashburn, Virginia, USA). 
 
Results and Discussion 
 
 
Water quality 
 
Ponds were constructed in soils of similar properties and filled with water from a 
single source; nevertheless, most water quality variables exhibited high variation which 
22 
 
 
 
 
will be illustrated using a variable that varied greatly, total ammonia nitrogen, and one 
that was less variable, total hardness.  On 26 August, concentrations of total ammonia 
nitrogen and total hardness ranged from 0.0 to 0.962 mg/L and from 127.2 to 209.6 mg/L, 
respectively among the nine ponds.  The farm means for this date were 0.204 ? 0.328 
mg/L for total ammonia nitrogen and 162.4 ? 33.2 mg/L for total alkalinity.  Over the 10 
sampling dates, farm means for total ammonia nitrogen were 0.0 to 0.376 mg/L, and 
those for total hardness were 152.1 to 210.5 mg/L.  The coefficients of variation for the 
farm means were 0.0 to 225.6% for total ammonia nitrogen, but from 16.1 to 25.0% for 
total hardness. 
When data for all sampling dates were averaged across each pond (pond means), 
total ammonia nitrogen varied from 0.060 ? 0.075 mg/L in Pond N-4 to 0.430 ? 0.168 
mg/L in Pond N-8; total hardness ranged from 126.8 ? 10.4 mg/L in Pond N-4 to 201.2 ? 
14.8 mg/L in Pond S-3.  Coefficients of variation for pond means were from 108.0 to 
193.6% for total ammonia nitrogen and 6.4 to 20.0% for total hardness. 
Considering all 79 measurements (ponds + dates), ranges were 0.0 to 2.057 mg/L 
for total ammonia nitrogen and 102.4 to 241.4 mg/L for total hardness.  These values had 
coefficients of variation of 185.4% and 22.0%, respectively.  The distribution of the 
values was highly skewed to the left for total ammonia nitrogen, but values were more 
normally distributed for total hardness (Fig. 1).  These observations and reference to 
other variables measured in the study suggest that variables controlled mainly by 
biological activity (carbon dioxide, dissolved oxygen, turbidity, chlorophyll a, Secchi 
disk visibility, and nitrogen and phosphorus fractions) are much more variable than 
variables controlled primarily by chemical and physical process (water temperature, pH, 
23 
 
 
 
 
salinity, conductivity, alkalinity, hardness, calcium, magnesium, and total dissolved 
solids). 
The data in this dissertation will be limited to farm means (average of all ponds 
on each date) and grand means (average of all ponds across all dates). 
Farm means for conductivity did not differ appreciably between surface and 
bottom water, but as a result of dilution by heavy rainfall in mid August, conductivity 
was greater during the first half as compared to the second half of the grow-out period 
(Fig. 2).  Individual measurements of conductivity in bottom water ranged from 4,538 to 
7,578 ?S/cm and had a grand mean of 5,880 ?S/cm (Table 2).  Total dissolved solids and 
salinity also were measured; grand means were 3,570 mg/L and 2.94 ppt, respectively 
(Table 2).  There was a high correlation between conductivity measurements and those 
for total dissolved solids and salinity (Fig. 3).  Changes in concentrations of total 
dissolved solids and salinity over time were not presented, because they followed the 
same trend as those presented for conductivity (Fig. 2). 
The culture species, L. vannamei, can tolerate salinities of 0.5 to 45 ppt (Bray et 
al. 1994, Menz and Blake 1980), and recent studies suggest that this species can possibly 
be cultured at salinity below 0.5 ppt (Araneda et al. 2008, Cuvin-Aralar et al. 2009).  
However, most successful shrimp culture appears to have been done at salinities above 2 
ppt (Roy et al. 2010).  Ponds of the present study always had over 2 ppt salinity, and 
salinity averaged 2.94 ppt (Table 2; Fig. 3), suggesting that waters in all ponds contained 
an adequate quantity of dissolved salts for production of the culture species.   
Mechanical aeration of ponds mixed pond water, and there was little difference in 
farm means between surface and bottom water temperature (Fig. 2; Table 2).  The grand 
24 
 
 
 
 
mean for water temperature was 28.82oC with individual values ranging from 20.48 to 
33.96oC.  The highest farm means for water temperatures were recorded in June, and 
values steadily decreased as the study progressed (Fig. 2).  The lowest temperatures were 
below optimum for culture of L. vannamei (Lester and Pante 1992), but these 
temperatures were recorded only in ponds harvested in late October.  Although low water 
temperature probably did not negatively impact shrimp growth during the grow-out 
period, low temperature on both ends of the grow-out period determines the length of the 
growing season for L. vannamei in the southeastern United States (Green and Popham 
2008).  The maximum water temperatures were no greater than those that have been 
observed in aquaculture ponds in tropical areas (Boyd and Tucker 1998). 
Farm means for pH tended to be slightly greater in surface water than in bottom 
water (Fig. 2).  This is typical in pond aquaculture, because removal of carbon dioxide by 
phytoplankton in surface water for use in photosynthesis causes pH to rise during 
daylight hours (Boyd and Tucker 1998).  Shrimp spend most of the time on the bottom, 
and the range in water pH in bottom water based on all individual measurements was 
7.27 to 9.37 (Table 2); pH above 9 was observed in 11 samples from eight ponds.  The 
minimum pH of 7.27 would not be harmful to the culture species.  Although mortality 
will not occur until pH rises to 10 or more, negative, sub-lethal effects may occur if pH 
rises above 9, and high pH results in a greater proportion of un-ionized ammonia that can 
be toxic to shrimp (Boyd and Tucker 1998). 
Farm means for dissolved oxygen concentration usually were 2 to 5 mg/L greater 
in surface water than in bottom water (Fig. 2) as would be expected because of greater 
photosynthetic rate in surface water.  Dissolved oxygen concentration in bottom water ? 
25 
 
 
 
 
was always measured near midday ? had a grand mean of 10.81 mg/L (Table 2).  A 
minimum value of 2.44 mg/L was recorded in an individual pond, and on three occasions, 
individual ponds had a concentration below 5 mg/L.  Occasional occurrence of low 
dissolved oxygen concentrations in bottom water near midday suggests that low 
dissolved oxygen concentration may be common in late evening and early morning.  
Most warmwater aquaculture species will not die until the dissolved oxygen 
concentration falls below 1.5 to 2 mg/L and remains at this level for several hours.  
However, exposure to dissolved oxygen levels below 3 or 4 mg/L for a shorter time may 
cause stress leading to greater susceptibility to disease, poor appetite, and slow growth 
(Boyd and Tucker 1998).  A study by McGraw et al. (2001) revealed that survival and 
production of shrimp improved in ponds as minimum, average daily oxygen 
concentrations increased from 1.1 mg/L to 4.6 mg/L.  The greatest improvement was 
noted when ponds with minimum concentration of 1.1 mg/L were compared with ponds 
where the minimum concentration was 2.8 mg/L. 
Carbon dioxide concentration (Fig. 2; Table 2) is difficult to assess because it also 
was measured near midday.  On some sampling dates, ponds had no free carbon dioxide 
as a result of phytoplankton photosynthesis, but in those that did, bottom water contained 
a greater carbon dioxide concentration than surface water because of greater 
photosynthetic rate in surface water.  Although the grand mean for carbon dioxide was 
only 4.66 mg/L in bottom waters, a peak individual concentration of 33.93 mg/L was 
measured, and concentrations above 10 mg/L were recorded on 14 occasions.  It is likely 
that high carbon dioxide concentrationsare common during late evening and early 
morning.  Carbon dioxide is not highly toxic to aquaculture species, but when dissolved 
26 
 
 
 
 
oxygen concentration is low, high carbon dioxide concentration interferes with 
absorption of oxygen from the water by culture species (Boyd and Tucker 1998). 
Farm means for total alkalinity concentration increased from near 120 mg/L in 
mid June to a maximum of about 180 mg/L in early October (Fig. 4).  The grand mean 
for total alkalinity concentration was 148.8 mg/L (Table 2) ? about 25 mg/L higher than 
the alkalinity of average seawater (Goldberg 1963).  The minimum alkalinity 
concentration of 71.5 mg/L observed in this study is slightly lower than the recommended 
minimum concentration for shrimp culture of 75 mg/L (Boyd et al. 2002).  However, 
only one sample had alkalinity below 75 mg/L, and alkalinity was less than 100 mg/L in 
only five samples.  Because samples were taken about midday when pH was often above 
8.3 because of photosynthesis, a fraction of the alkalinity in most samples resulted from 
carbonate (phenolphthalein alkalinity) (Fig. 4).  The difference in total alkalinity and 
methyl orange alkalinity in Fig. 4 represents phenolphthalein alkalinity.  
Farm means for total hardness increased from near 150 mg/L to about 200 mg/L 
during the study (Fig. 4).  Individual concentrations of this variable ranged from 102 to 
241 mg/L and the grand mean was 163.5 mg/L (Table 2).  Total hardness concentration 
was much less than that found in normal seawater (? 6,000 mg/L), and it was less than 
half of the total hardness of about 500 mg/L that could be expected in seawater diluted to 
the average salinity of the study ponds.  Calcium hardness made up about 60% of the 
total hardness (Fig. 4) ? magnesium hardness is the difference in total hardness and 
calcium hardness. 
Concentrations of magnesium and calcium, the cations primarily responsible for 
total hardness, were estimated from magnesium hardness and calcium hardness 
27 
 
 
 
 
concentrations:  magnesium hardness ? 4.12 = Mg2+; calcium hardness ? 2.5 = Ca2+ 
(Boyd 2000).  Farm means for magnesium and calcium concentration ranged from 12 to 
40 mg/L, respectively, in mid June to 18 and 50 mg/L, respectively, in late October.  The 
minimum concentrations of major cations needed for successful culture of shrimp and 
other marine animals in low-salinity water is not known.  Boyd et al. (2002) suggested 
that the seawater equivalent concentration ? the concentration of an ion expected in 
normal seawater diluted to the salinity of the culture system water ? should be an 
acceptable concentration, and Atwood et al. (2003) demonstrated that ionic proportions in 
diluted seawater are ideal for survival and growth of L. vannamei in low-salinity water.  
The grand mean for salinity of the study ponds equals to a seawater equivalent 
concentration of 31.5 mg/L for calcium and 106.5 mg/L for magnesium.  Calcium 
concentration as low as 21.3 mg/L was recorded, and calcium was below the seawater 
equivalent concentration in 15 samples.  The minimum magnesium concentration was 4.2 
mg/L, and all samples were below the seawater equivalent concentration. 
Potassium concentrations were not measured in this study, because a previous 
study showed that the farm manager added enough potassium fertilizer to ponds to 
maintain potassium concentration above the seawater equivalent concentration (Boyd et 
al. 2007, McNevin et al. 2004).  These previous studies also showed that sodium always 
exceeded the seawater equivalent concentration, and therefore, sodium was also not 
measured. 
Total ammonia nitrogen concentration was relatively low in the ponds (Fig. 5) 
despite the large inputs of feed.  Surface waters had relatively high pH that favors loss of 
un-ionized ammonia (NH3) to the air through diffusion (Gross et al. 1999, Weiler 1979).  
28 
 
 
 
 
The high rate of mechanical aeration used in ponds splashed water into the air, a process 
that also favors ammonia loss by diffusion to the air.  Ammonia nitrogen is rapidly 
absorbed by phytoplankton for use in protein synthesis (Tucker et al. 1984).  Moreover, 
ammonia is oxidized to nitrate by nitrifying bacteria (Boyd and Tucker 1998).  The 
highest recorded total ammonia nitrogen concentration in an individual pond was 2.06 
mg/L (Table 2), and on only three occasions did concentrations exceeded 1 mg/L. 
In laboratory toxicity tests, the 48-h LC50 of total ammonia nitrogen to L. 
vannamei was 39.7 mg/L for 47-day-old shrimp exposed at 29oC, pH 7.9, and 10 ppt 
salinity (Schuler et al. 2010).  This LC50 value equated to 2.09 mg/L un-ionized 
ammonia ? the toxic form.  However, the safe concentration for continuous exposure of 
aquaculture species to un-ionized ammonia is probably about 0.05 times the 48-h LC50 
(Boyd 2000).  Based on the findings of Schuler et al. (2010), shrimp should not be 
exposed to more than 0.1 mg/L un-ionized ammonia for long periods. 
In the present study, water temperature and pH sometimes exceeded 30oC and 9.0, 
respectively.  Under such conditions, more than 45% of total ammonia nitrogen would be 
in un-ionized form.  Total ammonia nitrogen concentrations could have temporarily 
exceeded, on several occasions, the limit considered safe for continuous exposure, and 
these events ? though not lethal ? might have stressed the shrimp. 
Nitrite-nitrogen was occasionally detected in pond waters (Fig. 5), and the 
maximum recorded concentration in an individual pond was 1.08 mg/L.  The 48-h LC50 
of nitrite was found to be 154 mg/L in laboratory toxicity tests (Schuler et al. 2010).  
Using an application factor of 0.05 (Boyd 2000), the minimum safe concentration for 
long-term exposure would be 7.7 mg/L ? considerably more than the maximum 
29 
 
 
 
 
concentration found in the ponds.  Nitrite toxicity does not seem to be a reasonable 
explanation for the variation in shrimp survival and production in Alabama ponds. 
Nitrate-nitrogen was seldom detectable in pond waters (Fig. 5).  This was an 
unexpected observation, because aquaculture ponds usually have nitrate-nitrogen 
concentrations of 0.1 to 0.3 mg/L (Boyd and Tucker 1998).  The major source of nitrate 
is oxidation of ammonia nitrogen, and ponds had low concentration of ammonia nitrogen 
? possibly, this is the reason for the lack of nitrate.  Of course, nitrate could have been 
reduced to nitrogen gas by denitrifying bacteria in anaerobic sediments (Hargreaves 
1998). 
Hydrogen sulfide, a substance that can be toxic at low concentrations to fish and 
shrimp (Boyd and Tucker 1998), was not detected in water from any of the ponds (Fig. 
5). 
Farm means for total nitrogen concentration steadily increased from about 5 mg/L 
in mid June to around 7 mg/L in late October (Fig. 5), and the grand mean was 5.86 mg/L 
(Table 2).  Contrary to total nitrogen, pond means for total phosphorus remained 
relatively constant, fluctuating from about 0.27 to 0.45 mg/L (Fig. 5), and the grand mean 
for total phosphorus was 0.36 mg/L (Table 2). 
Ponds usually had dense phytoplankton blooms as evident from high chlorophyll 
a concentration (Fig. 6); farm means steadily increased from about 160 ?g/L in mid June 
to around 575 ?g/L in early October.  The chlorophyll a concentration then declined with 
onset of lower temperatures (Fig. 6).  The grand mean for chlorophyll a was 464 ?g/L 
(Table 2). 
30 
 
 
 
 
Secchi disk visibility decreased as turbidity increased during the study (Fig. 6), 
and considering all measurements, the two variables were strongly correlated (r = 0.871; 
P < 0.01) (Fig. 7).  Both Secchi disk visibility and turbidity also were highly correlated 
with chlorophyll a concentration (P < 0.01), but Secchi disk visibility would be a better 
predictor of chlorophyll a concentration than would turbidity (Fig. 7).  Suspended 
particles that cause turbidity and lessen Secchi disk visibility in aerated ponds originate 
from two main sources ? phytoplankton and sediment particles suspended by aerator-
induced turbulence (Thomforde and Boyd 1991).  However, it is not clear why Secchi 
disk visibility was a better predictor of chlorophyll a concentration.   
The largest external input of inorganic nutrients and organic matter to ponds was 
feed, and feed input varied from 2,684 kg/ha to 9,558 kg/ha in the nine ponds.  The 
average concentrations of some water quality variables were correlated (P < 0.05) with 
feed input (Table 2).   
In summary, the water quality data suggest that several variables, water 
temperature, dissolved oxygen, carbon dioxide, total ammonia nitrogen, total alkalinity, 
calcium, and magnesium were at times outside optimum limits for shrimp production.  
Although these variables were never at toxic levels, but they may have stressed shrimp, 
and this could have negatively influence survival, feeding activity, growth rate, and 
production. 
 
Shrimp production 
 
Shrimp production data varied among the nine ponds (Table 3); survival and 
production ranged from 16% to 128%, and production had a range of 928 kg/ha to 5,950 
31 
 
 
 
 
kg/ha.  Because of the difficulty of counting tiny, postlarval shrimp, it is not unusual for 
counting errors to result in survival over 100%.  Low survival rates may also be caused 
by errors in estimating the number of postlarvae stocked.  Nevertheless, production was 
highly correlated with percentage survival (r = 0.912; P < 0.01) (Fig. 8).  Ponds were 
stocked during a short period (Table 1), but harvest was spread over a longer time (Table 
3).  This resulted in variation in the length of the grow-out period, but there was not a 
correlation between crop duration and production (Fig. 8). 
 
Correlations between production data and water quality 
 
The pond means (variables for each pond averaged across all dates) for water 
quality variables were used as X variables, and correlation analysis was conducted using 
both shrimp survival and shrimp production in each pond as Y variables (Table 4).  
Survival was positively correlated with increasing concentrations of total alkalinity, 
methyl orange alkalinity, calcium hardness, and total nitrogen, while it was negatively 
correlated with increasing water temperature, pH, and Secchi disk visibility.  Production 
was positively correlated with greater total alkalinity and methyl orange alkalinity, 
calcium hardness, and total nitrogen, but negatively correlated with higher water 
temperature and pH. 
Correlation of production with total nitrogen is not likely causal because ponds 
with high production had high survival and feed input, and total nitrogen concentration 
increased with greater feed input (Table 2).  The negative correlation between Secchi disk 
visibility and survival also is not thought to be causal.  Ponds with high survival had 
greater feed input, and more nutrients reached the water to stimulate phytoplankton 
32 
 
 
 
 
growth (decrease Secchi disk visibility).  Thus, low Secchi disk visibility would not be 
the cause of high survival, but rather, the result of it. 
Neither survival nor production was correlated with magnesium concentration.  
This suggests that the application of magnesium fertilizer to ponds provided sufficient 
magnesium to meet shrimp requirements albeit magnesium concentrations in the water 
were consistently below the seawater equivalent concentration.  The positive correlation 
between calcium hardness and both survival and production is interesting, because 
calcium ion has not been considered as a possible limitation in the ponds.  It was noted 
earlier that the calcium concentration was sometimes lower than the seawater equivalent 
concentration. 
Survival and production each were positively correlated with total alkalinity and 
methyl orange alkalinity.  However, calcium hardness tended to increase with increases 
in both total alkalinity and methyl orange alkalinity.  Thus, if a causal relationship exists 
for this group of variables, it is likely for calcium. 
Multiple linear regression (MLR) was used to investigate the relationship between 
water quality variables (independent variables) and shrimp production, feed conversion 
ratio, and survival rate (dependent variables).  The MLR modeling method was 
performed by the SAS 9.1.2 statistical analysis software (SAS Institute, 2008).  After 
obtained various equations with all independent and dependent variables mentioned 
above, the best equation is selected based on the highest multiple coefficient of 
determination (r2), lowest standard deviation (SD), and F-ration value.  The best model 
derived by the application of MLR method is: 
Production = -9455.37044 + 71.63166 (MetAlk) + 33.43784 (CaH)  
33 
 
 
 
 
The equation provides r2 = 0.9826 meaning that 98% of total variance for the estimation 
of production is explained by the MLR model for independent variables, methyl orange 
alkalinity (MetAlk) and calcium hardness (CaH), measured was statistically significant (P 
< 0.01) in estimating dependent variable, shrimp production in inland, low-salinity pond. 
Negative correlations between water temperature and pH and shrimp survival and 
production also merit further consideration.  However, it is possible that both may be 
related to cooler water temperature and lower daytime pH because of declining rates of 
photosynthesis during the final few weeks of culture in ponds of long crop duration that 
are harvested after mid September. 
Findings of this study did not identify any specific water quality conditions that 
were clearly out of balance and negatively affecting shrimp survival and production.  
However, the findings suggest that the farm should implement a daily monitoring 
program for early morning dissolved oxygen concentration to ascertain if the amount of 
aeration is sufficient to prevent dissolved oxygen concentrations below 3 mg/L.  Also, a 
weekly or twice weekly monitoring effort for total ammonia nitrogen concentration and 
pH could provide data for ascertaining if un-ionized ammonia nitrogen concentration is 
often great enough to stress shrimp. 
The correlation between calcium hardness and both survival and growth suggest 
that increasing calcium concentration might improve shrimp performance.  This 
hypothesis could be tested by applying calcium sulfate to a few ponds and comparing 
shrimp performance to that in other untreated ponds. 
 
 
34 
 
 
 
 
Literature Cited 
 
 
Araneda, M., E. P. P. rez , and E. Gasca-Leyva 2008. White shrimp Penaeus vannamei 
culture in freshwater at three densities: condition state based on length and 
weight. Aquaculture 283: 13-18. 
Atwood, H. L., S. P. Young, J. R. Tomasso, and Cl L. Browdy. 2003. Survival and 
growth of Pacific white shrimp Litopenaeus vannamei postlarvae in low-salinity 
and mixed-salt environments. Journal of the World Aquaculture Society 34: 
518-523. 
Bower, C. E. and T. Holm-Hansen. 1980. A salicylate-hypochlorite method for 
determining ammonia in seawater. Canadian Journal of Fisheries and Aquatic 
Sciences 37: 794-798. 
Boyd, C. A., C. E. Boyd, and D. B. Rouse. 2007. Potassium budget for inland, saline 
water shrimp ponds in Alabama. Aquacultural Engineering 36: 45-50. 
Boyd, C. E. 2000. Water quality: an introduction. Kluwer Academic Publishers, Boston, 
Massachusetts, USA. 
Boyd, C. E. and C. S. Tucker. 1992. Water quality and pond soil analyses for 
aquaculture. Alabama Agricultural Experiment Station, Auburn University, 
Alabama, USA. 
Boyd, C. E. and C. S. Tucker. 1998. Pond aquaculture water quality management. 
Kluwer Academic Publishers, Boston, Massachusetts, USA 
Boyd, C. E., T. Thunjai, and M. Boonyaratpalin. 2002. Dissolved salts in water for 
inland, low salinity shrimp culture. Global Aquaculture Advocate 5: 40-45. 
35 
 
 
 
 
Bray , W. A., A. L. Lawrence, and J. R. Leung-Trujillo. 1994. The effect of salinity 
on growth and survival of Penaeus vannamei, with observations on the 
interaction of IHHN virus and salinity. Aquaculture 122: 133-146. 
Cuvin-Aralar, M. L. A., A. G. Lazartigue, and E. V. Aralar. 2009. Cage culture of 
Pacific white shrimp Litopenaeus vannamei (Boone, 1931) at different stocking 
densities in a shallow eutrophic lake. Aquaculture Research 40: 181-187. 
Eaton, A. D., L. S. Clesceri, E. W. Rice, and A. E. Greenberg. 2005. Standard 
methods for the examination of water and wastewater, 21st edition. American 
Public Health Association, Washington, D.C., USA. 
Goldberg, E. D. 1963. Chemistry - the oceans as a chemical system. In: M. N. Hill (ed.), 
Composition of sea water, comparative and descriptive oceanography. Vol. II 
The Sea. Interscience Publ., New York: 3-25. 
Green, B. W. and T. W. Popham.  2008. Probabiliteis of low nightime temperatures 
during stocking and harvest seasons for inland shrimp culture. Journal of the 
World Aquaculture Society 39: 1-103. 
Gross, A., C. E. Boyd, and J. Seo. 1999. Evaluation of the ultraviolet 
spectrophotometric method for the measurement of total nitrogen in water. 
Journal of the World Aquaculture Society 30: 388-393. 
Gross, A., C. E. Boyd, and C. W. Wood. 1999. Ammonia volatilization from freshwater 
ponds. Journal of Environmental Quality 28: 793-797. 
Hargreaves, J. A. 1998. Nitrogen biogeochemistry of aquaculture ponds. Aquaculture 
166: 181-212. 
36 
 
 
 
 
Lester, L. J. and Ma. J. R. Pante. 1992. Penaeid temperature and salinity responses, 
pages 515-534. In: A. Fast and L. J. Lester (editors),  Marine Shrimp Culture: 
Principles and Practices. Elsevier Science Publishers, Amsterdam, The 
Netherlands. 
McGraw, W., D. R. Teichert-Coddington, D. B. Rouse, and C. E. Boyd. 2001. Higher 
minimum dissolved oxygen concentrations increase penaeid shrimp yields in 
earthern ponds. Aquaculture 199: 311-321. 
McNevin, A., C. E. Boyd, O. Silapajarn, and K. Silapajarn. 2004. Ionic 
supplementation of pond waters for inland culture of marine shrimp. Journal of 
the World Aquaculture Society 35: 460-467. 
Menz, A. and B. F. Blake. 1980. Experiments on the growth of Penaeus vannamei 
Boone. Journal of Experimental Marine Biology and Ecology 48: 99-111. 
Roy, L. A., D. A. Davis, I. P. Saoud, C. A. Boyd,  H. J. Pine, and C. E. Boyd. 2010. 
Shrimp culture in inland low salinity waters. Reviews in Aquaculture 2: 191-
208. 
Schuler, D. J., G. D. Boardman, D. D. Kuhn, and G. J. Flick. 2010. Acute toxicity of 
ammonia and nitrite to Pacific white shrimp, Litopenaeus vannamei at low 
salinities. Journal of the World Aquaculture Society 41: 438-446. 
Thomforde, H. and C. E. Boyd. 1991. Effects of aeration on water quality and channel 
catfish production. Bamidgeh (Israeli Journal of Aquaculture) 43: 3-26. 
Tucker, C. S., S. W. Lloyd, and R. L. Busch. 1984. Relationships between 
phytoplankton periodicity and concentrations of total and un-ionized ammonia 
in channel catfish ponds. Hydrobiologia 111: 75-79. 
37 
 
 
 
 
van Rijn, J. 1993. Methods to evaluate water quality in aquaculture. Faculty of 
Aquaculture. The Hebrew University of Jerusalem, Rehovot, Israel (in Hebrew). 
Weiler, R. R. 1979. Rate of loss of ammonia from water to the atmosphere. Journal of 
the Fisheries Research Board of Canada 36: 685-689. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
38 
 
 
 
 
Table 1.  Pond information and data on stocking, aeration, and feed application in nine 
ponds on an inland, low-salinity shrimp farm in Alabama. 
Pond Area (ha) Average  Depth (m) 
Stocking data Aeration 
(hp/ha) 
Feed applied 
(kg/ha) Date PL/m2 
N2 0.57 1.64 7 Jun 26.95 8.8 4,805 
N4 1.21 1.62 23 Apr 16.08 10.7 4,623 
N6 1.50 1.60 22 May 25.02 9.7 5,779 
N7 2.02 2.07 22 May 19.25 13.0 5,821 
N8 1.54 1.76 22 May 22.34 9.7 6,525 
S1 1.17 1.26 21 May 27.94 8.5 4,490 
S3 1.01 1.29 21 May 29.70 12.9 4,682 
S6 1.42 1.63 22 May 25.00 9.2 2,684 
S8 1.94 1.57 21 May 27.89 11.9 9,558 
 
 
 
 
 
 
 
 
 
 
 
39 
 
 
 
 
Table 2.  Grand means and standard deviations for water quality variables measured at 2-
wk intervals for nine ponds on an inland, low-salinity shrimp farm in Alabama.  
Correlation coefficients (r) between total feed input and water quality variables also are 
given. 
 
* Significant at P < 0.05 
 
 
Variable Mean Min Max r 
Total ammonia nitrogen (mg/L) 0.191?0.353 0.00 2.057 0.486 
Nitrite-nitrogen (mg/L) 0.033?0.142 0.00 1.098 - 
Nitrate-nitrogen (mg/L) 0?0.004 0.00 0.037 - 
Total phosphorus (mg/L) 0.36?0.12 0.12 0.66   0.687* 
Total nitrogen (mg/L) 5.85?2.24 2.32 14.91 0.593 
Hydrogen sulfide (mg/L)  0.00?0.00 0.00 0.00 - 
Carbon dioxide at the surface (mg/L) 2.05?5.79 0.00 30.50   0.870* 
Carbon dioxide at the bottom (mg/L)  4.66?8.34 0.00 35.25   0.901* 
Dissolved oxygen at the surface (mg/L) 13.48?4.28 5.40 26.20 0.138 
Dissolved oxygen at the bottom (mg/L) 10.81?4.28 2.40 26.00 0.077 
pH at the surface 8.56?0.51 7.50 9.80  -0.883* 
pH at the bottom 8.33?0.48 7.30 9.40  -0.924* 
Temperature at the surface (oC)  29.43?3.39 20.51 35.80  -0.893* 
Temperature at the bottom (oC) 28.82?3.03 20.48 33.96  -0.809* 
Salinity (ppt) 2.94?0.31 2.15 3.84 0.164 
Conductivity at the surface ( ?S/cm) 5,948?733 4,551 7,740 0.061 
Conductivity at the bottom ( ?S/cm) 5,880?704 4,538 7,578 0.061 
Phenolphthalein alkalinity (mg/L as 6.32?5.38 0.00 24.42    -0.629 
Methyl orange alkalinity (mg/L as 137.5?30.9 59.90 209.5 0.761 
Total alkalinity (mg/L as CaCO3) 143.8?28.8 71.40 212.2   0.756* 
Total hardness (mg/L as CaCO3) 163.5?36.0 102.4 241.3 0.615 
Calcium hardness (mg/L as CaCO3) 96.1?26.6 53.20 157.1   0.787* 
Magnesium hardness (mg/L as CaCO3) 67.4?18.8 17.10 120.3 0.573 
Secchi disk visibility (cm) 24.8?9.8 12 60  -0.697* 
Turbidity (NTU) 56.5?35.1 12.80 208   0.726* 
Chlorophyll a ( ?g/L) 463?302 29 1,467 0.551 
Total dissolved solids (mg/L) 3,570?358 2,670 4,567 0.170 
40 
 
 
 
 
Table 3.  Harvest data and production performance in nine ponds on an inland, low-
salinity shrimp farm in Alabama. 
Pond 
 Harvest data  Crop duration 
(days) Survival FCR  Date Shrimp/m2 (kg/ha)  
N2  7 Oct 17.59 4,066   122 65 1.18 
N4  29 Sep 10.42 2,781   159 65 1.66 
N6  21 Oct 15.31 3,142   152 61 1.84 
N7  23 Oct 24.54 4,406   154 128 1.32 
N8  26 Oct 23.38 4,656   157 105 1.40 
S1  1 Oct 11.65 2,506   133 42 1.79 
S3  6 Oct 10.16 2,453   138 34 1.91 
S6  19 Sep   4.01 928   120 16 2.89 
S8  29 Oct 33.50 5,950   161 120 1.61 
 
 
 
 
 
 
 
 
 
 
 
41 
 
 
 
 
Table 4.  Correlation coefficients among water quality variables and shrimp survival and 
production in nine ponds at an inland, low-salinity shrimp farm in Alabama. 
* Significant at P < 0.05 
 
 
 
 
 
 
X-Variable 
Y-Variable 
Survival Production 
Conductivity   0.114  0.104 
Water temperature   -0.782*  -0.779* 
pH   -0.834*  -0.879* 
Total alkalinity    0.754*    0.832* 
Methyl orange alkalinity    0.814*    0.897* 
Phenolphthalein alkalinity -0.496 -0.473 
Total hardness   0.564  0.587 
Calcium hardness     0.671*    0.692* 
Magnesium hardness   0.192  0.200 
Total ammonia nitrogen   0.574  0.469 
Total nitrogen   0.622    0.667* 
Total phosphorus   0.377  0.435 
Chlorophyll a   0.579 -0.437 
Secchi disk visibility    -0.701* -0.555 
Turbidity    0.192   0.089 
   
 
 
 
 
 
Fig. 1.  Distribution of concentrations of total ammonia nitrogen and total hardness 
measured in nine ponds at 2
Alabama. 
 
 
 
 
 
 
 
0
10
20
30
40
50
60
0.00
Nu
mb
er 
of 
sam
ple
s
0
5
10
15
20
25
<100
Nu
mb
er 
of 
sam
ple
s
42 
-wk intervals at an inland, low-salinity, shrimp farm in 
0.01-0.05 0.051-1.00 1.01-1.50 1.51-2.00
Total ammonia nitrogen (mg/L)
101-125 126-150 151-175 176-200 201-225
Total hardness (mg/L as CaCO3)
 
 
>2.00
>225
43 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 2.  Farm means (all ponds averaged by date) and standard deviations for 
conductivity, water temperature, pH, dissolved oxygen, and carbon dioxide in nine ponds 
at an inland, low-salinity shrimp farm in Alabama. 
 
Jun 16 30 Jul 14 28Aug 1126 Sep 9 18 Oct 7 21
Co
nd
uc
tiv
ity
 (u
S/c
m)
4500
5000
5500
6000
6500
7000
7500
Jun 16 30 Jul 14 28 Aug 11 26 Sep 9 18 Oct 7 21
pH
7.0
7.5
8.0
8.5
9.0
9.5
10.0
Surface
Bottom
Jun 16 30 Jul 14 28 Aug 11 26 Sep 9 18 Oct 7 21
Di
sso
lve
d o
xy
ge
n (
mg
/L
)
0
5
10
15
20
25
30
Surface
Bottom
Jun 16 30 Jul 14 28 Aug 11 26 Sep 9 18 Oct 7 21
Ca
rb
on
 di
ox
ide
 (m
g/L
)
0
5
10
15
20
25
30
Surface
Bottom
Jun 16 30 Jul 14 28 Aug 11 26 Sep 9 18 Oct 7 21
Te
mp
era
tur
e (
o C
)
18
20
22
24
26
28
30
32
34
36
Bottom 
Surface 
44 
 
 
 
 
 
Fig. 3.  Correlations between conductivity and salinity and total dissolved solids in waters 
of ponds at an inland, low-salinity shrimp farm in Alabama. 
  
y = 0.0004x + 0.7803
r = 0.854
P < 0.01
0
1
2
3
4
5
4,000 5,000 6,000 7,000 8,000 
Sal
ini
ty 
(pp
t)
Conductivity (?S/cm)
y = 0.4425x + 953.24
r = 0.887
P < 0.01
2,000 
2,500 
3,000 
3,500 
4,000 
4,500 
5,000 
4,000 5,000 6,000 7,000 8,000 
Tot
al 
dis
sol
ve
d s
oli
ds
 (m
g/L
)
Conductivity (?S/cm)
45 
 
 
 
 
 
 
 
 
 
 
 
Fig. 4.  Farm means (all ponds averaged by date) and standard deviations for total 
alkalinity and methyl orange alkalinity and total hardness and calcium hardness in nine 
ponds at an inland, low-salinity shrimp farm in Alabama. 
 
 
 
 
\ 
 
 
 
 
Jun 16 30 Jul 14 28 Aug 11 26 Sep 9 18 Oct 7 21
Al
ka
lin
ity
 (m
g/L
 as
 C
aC
O 3
)
60
80
100
120
140
160
180
200
220 Methyl orange alkalinity
Total alkalinity
Jun 16 30 Jul 14 28 Aug 11 26 Sep 9 18 Oct 7 21
Ha
rd
ne
ss 
(m
g/L
 as
 C
aC
O 3
)
0
50
100
150
200
250
300 Total hardness 
Calcium hardness 
46 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 5.  Farm means (all ponds averaged by date) and standard deviations for hydrogen 
sulfide, nitrite-nitrogen, total ammonia nitrogen, nitrate-nitrogen, total nitrogen, and total 
phosphorus in nine ponds at an inland, low-salinity shrimp farm in Alabama. 
  
Jun 16 30 Jul 14 28 Aug 11 26 Sep 9 18 Oct 7 21
mg
/L
0.0
0.2
0.4
0.6
Nitrite-nitrogen
Hydrogen sulfide
Jun 16 30 Jul 14 28 Aug 11 26 Sep 9 18 Oct 7 21
mg
/L
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Total ammonia nitrogen
Nitrate-nitrogen
Jun 16 30 Jul 14 28 Aug 11 26 Sep 9 18 Oct 7 21
To
tal
 ni
tro
ge
n (
mg
/L
)
2
4
6
8
10
12
Jun 16 30 Jul 14 28 Aug 11 26 Sep 9 18 Oct 7 21
To
tal
 ph
osp
ho
ru
s (
mg
/L
)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
47 
 
 
 
 
 
 
 
 
 
 
Figure 6.  Farm means (all ponds averaged by date) and standard deviations for Secchi 
disk visibility, turbidity, and chlorophyll a in waters of nine ponds on an inland, low-
salinity shrimp farm in Alabama. 
 
 
 
 
 
 
 
 
 
Jun 16 30 Jul 14 28 Aug 11 26 Sep 9 18 Oct 7 21
Ch
lor
op
hy
ll a
 (u
g/L
)
0
200
400
600
800
1000
1200
Jun 16 30 Jul 14 28 Aug 11 26 Sep 9 18 Oct 7 21S
ecc
hi 
dis
k v
isi
bil
ity
 (c
m)
, T
ur
bid
ity
 (N
TU
)
0
20
40
60
80
100
120
140
Secchi disk visibility 
Turbidity 
48 
 
 
 
 
 
 
 
Fig. 7.   Regression lines and correlation coefficients (r) for relationships among Secchi 
disk visibility, turbidity, and chlorophyll a data collected from nine ponds over the grow-
out season at an inland, low-salinity shrimp farm in Alabama. 
y = 3710.6x-1.381
r = 0.871
P < 0.01
0
50
100
150
200
250
0 25 50 75
Tu
rb
idi
ty 
(N
TU
)
Secchi disk visibility (cm)
y = 206178x-2.041
r = 0.876
P < 0.01
0
400
800
1,200
1,600
0 25 50 75
Ch
lor
op
hyl
l a
(ug/
L)
Secchi disk visibility (cm)
y = 5.5841x1.0571
r = 0.564
P < 0.01
0
400
800
1,200
1,600
0 100 200 300
Ch
lor
op
hyl
l a
(ug/
L)
Turbidity (NTU)
49 
 
 
 
 
 
Fig. 8.  Correlation between survival and crop duration and production of shrimp at an 
inland, low-salinity shrimp farm in Alabama. 
 
 
 
 
 
 
 
 
 
 
 
 
r = 0.912
P < 0.01
0 
1,000 
2,000 
3,000 
4,000 
5,000 
6,000 
7,000 
0 50 100 150
Sh
rim
p p
rod
uc
tion
 (k
g/h
a)
Survival rate (%)
r = 618
P > 0.05
0 
1,000 
2,000 
3,000 
4,000 
5,000 
6,000 
7,000 
0 50 100 150 200 250
Sh
rim
p p
rod
uc
tion
 (k
g/h
a)
Crop duration (days)
50 
 
 
 
 
 
 
 
 
 
IV.  Trace Elements in Waters of Inland, Low-Salinity Shrimp Ponds in Alabama 
 
Abstract 
 
 
Concentrations of 18 trace elements in waters of ten inland, low-salinity shrimp 
ponds in Alabama tended to be greater than concentrations found in normal seawater ? 
molybdenum, boron and silicon were exceptions. Concentrations of most trace elements 
varied greatly among ponds on individual sampling dates, and averages based on all 
sampling dates in individual ponds also varied considerably.  The analytical method used, 
digestion of water samples in nitric acid followed by inductive coupled plasma 
spectrophotometry, measured total concentrations of trace elements.  However, only the 
free ionic forms of most trace elements are toxic to aquatic life, and hydrolysis products, 
ion pairs, and coordination compounds (chelated forms) of most trace elements 
contributed greatly to total concentration.  Although measured concentrations of iron, 
aluminum, zinc, and selenium were occasionally higher than typical, safe concentration 
limits for continuous exposure to aquatic life, it is doubtful that free ionic concentrations 
of these trace elements were great enough to harm shrimp.  Positive correlations (P < 
0.05) between shrimp survival and production, and increasing concentrations of zinc, 
cobalt, and iron should be investigated further to ascertain if additions of these elements 
to ponds might improve shrimp performance. 
 
51 
 
 
 
 
Introduction 
 
 
Groundwater of 2 to 10 ppt salinity from wells is used in ponds for inland culture 
for Pacific white shrimp L. vannamei in Alabama.  Shrimp survival and production in this 
water is limited by low concentrations of potassium and possibly of magnesium (Davis et 
al. 2005, Roy et al. 2010).  Applications of potassium and magnesium fertilizers are used 
to overcome these deficiencies and allow survival rates and production levels similar to 
those obtained in coastal shrimp ponds filled with seawater or brackish water (Boyd et al. 
2007, McNevin et al. 2004).  Nevertheless, producers still complain about variation in 
survival and production among ponds. 
A study of commonly measured water quality variables in inland, low-salinity 
shrimp ponds in Alabama conducted in 2008 revealed that several variables occasionally 
were outside optimum concentration ranges.  There also were correlations between both 
survival and growth of shrimp and total alkalinity, calcium, water temperature, and pH 
that deserve further investigation.  However, trace element concentrations were not 
considered in the earlier study, and the present study was undertaken to assess possible 
effects of trace elements on shrimp in inland, low-salinity ponds. 
 
 
 
 
 
 
 
52 
 
 
 
 
Materials and Methods 
 
 
Ten ponds in which farm managers observed low survival, low production, or 
both in previous crops were selected for study.  Ponds are located on three shrimp farms 
in a fairly small area (6-km radius) of southeastern Greene County in the Blackland 
Prairie region of Alabama.  Farms will be designated as A (seven ponds), B (two ponds), 
and C (one pond).  Ponds were built in clayey, slightly alkaline soils typical of the 
Blackland Prairie region (Hajek et al. 1975) and filled from wells from the same saline-
water aquifer. 
Reliable information on ponds and their management were available only for 
Farm A (Table 1).  The seven ponds ranged from 0.57 to 1.94 ha in water surface area, 
and they had average depths of 1.16 to 1.49 m.  Postlarval shrimp (PL) were stocked in 
May 2009 at rates of 15.0 to 28.2 PL/m2.  A pelleted, 35% crude protein feed was applied 
twice daily, and total feed input varied from 4,967 to 8,688 kg/ha.  Aeration rates in 
ponds were 8.5 to 11.8 hp/ha and aerators were operated mainly at night.  Ponds at Farm 
B were of comparable size to those at Farm A, but the pond at Farm C was about 10-ha in 
area.  Ponds at Farms B and C had aeration rates similar to those used at Farm A, and 
stocking rates and feed inputs also were thought to be comparable. 
Surface water samples were collected from ponds at 2-wk intervals between 6 
May and 6 October 2009.  The samples were placed in 100-mL, plastic bottles preserved 
with 50% nitric acid (2.0 mL/100 mL), and transported to Auburn University for analysis.  
Samples were digested by a slight modification of Method EPA 200.8 (Revised 5.4) 
(United States Environmental Protection Agency 1994).  A 50-mL aliquot of each 
acidified sample was transferred to a 125-mL Erlenmeyer flask, and the sample was 
53 
 
 
 
 
heated on a hot plate until about 5-mL remained.   Following filtration, the sample was 
quantitatively transferred to a 50-mL volumetric flask and made to volume with glass-
distilled water.  The solution was analyzed by inductive coupled plasma spectrometry 
(SpectroCiros CCD, SPECTRO Analytical Instruments, Inc., Mahwah, New Jersey, USA) 
for aluminum (Al), arsenic (Ar), barium (Ba), boron (B), cadmium (Cd), chromium (Cr), 
cobalt (Co), copper (Cu), lead (Pb), iron (Fe), manganese (Mn), molybdenum (Mo), nikel 
(Ni), selenium (Se), silicon (Si), titanium (Ti), zinc (Zn), and zirconium (Zr). 
Shrimp samples from three ponds and feed samples were obtained at Farm A.  
The samples were dried at 60oC in a mechanical convection oven and pulverized with a 
mortar and pestle.  Aliquots of samples were ashed in a muffle furnace for 8 h at 450oC, 
and ash was dissolved in 1.0 N nitric acid as described by Boyd and Teichert-
Coddingtion (1995).  Resulting solutions were passed through Whatman Number 42, 
acid-washed, filter papers, and analyzed for trace elements by inductive coupled plasma 
spectrophotometry. 
Production data were obtained following harvest of ponds, but survival 
percentage and crop duration were available only for farm A.  Data on feed input and 
composition were used to estimate the amount of each trace element added to each pond 
in feed.  Trace element concentrations were averaged across all sampling dates for each 
pond.  Correlation coefficients were determined for trace element inputs in feed (X 
variable) and mean pond water concentrations of trace elements.  Correlation coefficients 
also were obtained for mean concentrations of trace elements (X variable) and shrimp 
survival in ponds at Farm A and shrimp production for all ponds.  Statistical analyses 
54 
 
 
 
 
were conducted by aid of SigmaPlot statistical software version 10.0 (Aspire Software 
International, Ashburn, Virginia, USA). 
 
Results and Discussion 
 
 
Variation in concentrations of trace elements among ponds on each sampling date 
exhibited variation similar to that shown for Pond N-8 at Farm A (Fig. 1) for six essential 
elements, boron, iron, copper, zinc, molybdenum and cobalt, and two non-essential ones, 
lead and nickel.  The range in average concentrations of trace elements for sampling 
dates also was wide; for example, zinc concentration averaged between 14.8 ? 2.7 ?g/L 
on 6 May to 41.8 ? 14.3 ?g/L on 14 July, while molybdenum concentration averaged 
from 1.22 ? 0.92 ?g/L on 14 July to 4.00 ? 2.45 ?g/L on 28 July.  Coefficients of 
variation ranged 7.5 to 34.2% for zinc and from 46.6 to 100% for molybdenum.  As 
shown in Fig. 1 for Pond N-8, no trends of increase or decrease in concentrations of trace 
elements with respect to time were noted in individual ponds.    
A similar degree of variation was observed when concentrations for all sampling 
dates were averaged for each pond.  For example, zinc concentrations ranged from 17.4 ? 
2.6 to 25.3 ? 10.0 ?g/L and molybdenum concentration varied from 0.74 ? 0.80 to 4.18 ? 
2.32 ?g/L in individual ponds. 
Standard deviations, coefficients of variation, and ranges for grand means of 
individual variables are presented (Table 2).  The coefficients of variation allow a 
comparison of the degree of variability of different trace elements; they ranged from 
27.9% for boron to 400% for zirconium.  Ten of the 18 variables had coefficients of 
variation above 100%.  The ponds are all built in similar soil and filled with water from 
55 
 
 
 
 
the same aquifer.  One of the ponds at Farm B was previously used for channel catfish 
Ictalurus punctatus culture and had been treated repeatedly in the past with copper sulfate 
to control blue-green algae responsible for off-flavor (Tucker 1996, McNevin and Boyd 
2004).  The high, average concentration of copper in this pond, 34.2 ?g/L, as compared 
to those of other ponds, 1.9 to 6.7 ?g/L, was no doubt the result of previous copper 
additions.  Otherwise, the main input of trace elements to ponds besides the water source 
was feed.  However, there were no correlations (P > 0.05) between the amounts of feed 
applied to ponds at Farm A and the concentrations of trace elements (Table 2). 
Average concentrations of trace elements ? other than molybdenum, boron, and 
silicon ? in waters of the inland shrimp ponds were generally higher than concentrations 
of these elements in normal seawater (Goldberg 1963).  Concentrations of most trace 
elements were within typical ranges reported for freshwater lakes, ponds, and streams 
(Arce and Boyd 1980, Boyd and Tucker 1998, Hem 1970, Hutchinson 1957).  This 
difference probably reflects the influence of prolonged contact of saline groundwater and 
pond water with soil and other geological formations.  Moreover, it suggests that inland, 
low-salinity shrimp ponds have higher concentrations of most trace elements than coastal 
ponds filled with water of marine origin.  
Free ionic forms of most trace elements are not highly soluble in water even if 
they are relatively abundant in geological material with which water has been in contact 
(Boyd 2000, Hem 1970).  Concentration of ionic iron, manganese, copper, zinc, cobalt, 
and aluminum are particularly low in waters with pH above 5 or 6 (Boyd 2000).  The 
measured concentration of a trace element, however, usually is several fold greater than 
expected at equilibrium between its mineral form(s) in geological material and its free, 
56 
 
 
 
 
ionic form in natural water.  This results because common analytical procedures such as 
the one used in this study measure soluble hydrolysis products such as Fe(OH)2+, 
Fe(OH)4? , Al(OH)2+, and AL(OH)4? , etc., ion pairs such as CuCO3? and ZnCl2?, etc., and 
coordination compounds formed through chelation of positively charged metal ions by 
dissolved organic matter (Schindler 1967; Boyd 2000).  Moreover, iron and aluminum 
contained on colloidal clay particles is detected by the analytical method used in this 
study. 
The toxicity of most trace elements to aquatic organisms is related to 
concentrations of their free, ionic forms (Boyd 2000, Pagenkoff 1978).  Because of this, it 
is difficult to predict toxicity of trace elements to shrimp and other organisms directly 
from concentrations measured by normal analytical procedures.  Moreover, most data on 
toxicity of trace elements were developed for a few, selected species of freshwater fish 
(Boyd and Tucker 1998), and almost no information related specifically to shrimp and 
particularly to L. vannamei could be found.  However, it is likely that the sensitivity of 
farm-reared shrimp to trace elements is similar to that of common species of freshwater 
fish (Boyd and Tucker 1998). 
Assuming the worst case scenario of measured concentrations of trace elements 
being equal to free ionic concentrations, aluminum, iron, selenium, and zinc 
concentrations in some samples exceeded safe concentrations reported for aquatic life  
(Table 3).  However, as already discussed, there is little free aluminum ion in pond water 
unless pH is below 6, and pond waters in this study typically had pH of 7 to 9.  
Aluminum toxicity can be accounted as a factor influencing shrimp survival and 
production.  Iron exceeded the safe concentration limit in 13 samples, but again, at the pH 
57 
 
 
 
 
of the ponds, most of the iron was in hydrolysis products, ion pairs, and coordination 
compounds that are not toxic.  Zinc was 1 to 12 ?g/L above the reported safe limit of 50 
?g/L (Table 3) in three samples, and not thought to have been toxic.  Selenium, however, 
exceeded the safe limit of 10 ?g/L in 21 samples that had from 11 to 22 ?g/L.  Thus, 
selenium is the only trace element that possibly had a negative influence on shrimp. 
Complete data on shrimp production were available only from ponds at Farm A 
(Table 4).  Ponds had production of 3,005 to 5,425 kg/ha, survival rates of 32.6 to 95.2% 
and feed conversion ratios (FCRs) of 1.28 to 2.37.  Production in the two ponds at Farm 
B was 2,989 and 3,297 kg/ha.  The pond at Farm C had a production of 3,363 kg/ha. 
The influence of trace element concentrations on shrimp was further assessed by 
correlation analysis (Table 5).  There were no negative correlations (P > 0.05) between 
concentrations of trace elements in pond water and percentage survival or production of 
shrimp.  This supports the conclusion above that concentrations of trace elements ? 
including selenium ? were not high enough to harm shrimp.  
Several elements uni2500 iron, manganese, copper, zinc, cobalt, and possibly others uni2500 
are essential for shrimp.  Except for copper, feed contained a greater amount of each trace 
element than was contained in shrimp at harvest.  Nevertheless, there was no correlation 
(P > 0.05) between copper in water and shrimp survival.  There was a positive correlation 
(P < 0.05) between concentrations of zinc and cobalt in the water and shrimp survival 
(Table 3).  The positive correlation between lead concentration in water and shrimp 
survival is probably not causal, because lead is not an essential element for animals (Pais 
and Jones1997). 
58 
 
 
 
 
Shrimp production was positively correlated (P < 0.05) with cobalt, iron, and zinc 
concentrations in the water, and FCR was negatively correlated uni2500 became less uni2500 with 
greater concentrations of lead and zinc.  There is no reason to believe that lead would be 
beneficial to FCR, but zinc is an essential element. 
Findings of this study suggest that trace element concentrations in waters of 
inland shrimp ponds in Alabama do not reach toxic levels.  However, correlations found 
between survival, production, and FCR and concentrations of cobalt, iron, and zinc 
deserve further study to ascertain whether or not they are causal.  Feed contained more 
cobalt, iron, and zinc than present in shrimp.  Thus, assuming that the correlations of 
these three elements with shrimp performance are causal, the reason might be because of 
an increase in the quantity, nutritional quality, or both of natural food organisms that 
shrimp eat in addition to manufactured feed.  This possibility could be investigated by 
comparing production results in ponds fertilized with cobalt, iron, and zinc compounds 
with those obtained in ponds untreated with trace elements. 
 
 
 
 
 
 
 
 
 
59 
 
 
 
 
Literature Cited 
 
 
Arce, R. G., and C. E. Boyd. 1980. Water chemistry of Alabama ponds. Bulletin 522, 
Alabama Agricultural Experiment Station, Auburn University, Alabama, USA.  
Australian and New Zealand Environment and Conservation Council. 1992. 
Australian water quality guidelines for fresh and marine waters. Australian and 
New Zealand Environment and Conservation Council, Canberra, Australia. 
Boyd, C. A., C. E. Boyd, and D. B. Rouse. 2007. Potassium budget for inland, saline 
water shrimp ponds in Alabama. Aquacultural Engineering 36: 45-50. 
Boyd, C. E. 2000. Water quality: an introduction. Kluwer Academic Publishers, Boston, 
Massachusetts, USA. 
Boyd, C. E., and C. S. Tucker. 1998. Pond aquaculture water quality management. 
Kluwer Academic Publishers, Boston, Massachusetts, USA. 
Boyd, C. E., and D. R. Teichert-Coddington. 1995. Dry matter, ash, and elemental 
composition of pond-cultured Penaeus vannamei and P. stylirostis. Journal of 
the World Aquaculture Society 26: 88-92. 
Davis, D. A., C. E. Boyd, D. B. Rouse, and I. P. Saoud. 2005. Effects of potassium, 
magnesium, and age on growth and survival of Litopenaeus vannamei 
postlarvae reared in inland low salinity well waters in west Alabama. Journal of 
the World Aquaculture Society 36: 416-419. 
Goldberg, E. D. 1963. Chemistry - the oceans as a chemical system, pages 3-25.  In: M. 
N. Hill (ed.), Composition of sea water, comparative and descriptive 
oceanography, Volume II, The Sea. Interscience Publishers, New York, New 
York, USA. 
60 
 
 
 
 
Hajek, B. F., F. L. Gilbert, and C. A. Steers. 1975. Soil associations of Alabama. 
Department of Agronomy and Soils Departmental Series No. 24, Alabama 
Agricultural Experiment Station, Auburn University, Alabama, USA. 
Hem, J. D. 1970. Study and interpretation of the chemical characteristics of natural 
water. U.S. Geological Survey, Water-Supply Paper 1473. U.S. Government 
Printing Office, Washington, D.C. , USA. 
Hutchinson, G. E. 1957. A treatise on limnology: Vol. I. Geography, Physics, and 
Chemistry. John Wiley and Sons, New York, New York, USA.. 
McNevin, A. A., C. E. Boyd, O. Silapajarn, and K. Silapajarn. 2004. Ionic 
supplementation of pond waters for inland culture of marine shrimp. Journal of 
the World Aquaculture Society 35: 460-467. 
McNevin, A. A. and. C. E. Boyd. 2004. Copper concentration in Channel catfish 
Ictalurus punctatus ponds treated with copper sulfate. Journal of the World 
Aquaculture Society 35: 16-24. 
Pagenkoff, G. K. 1978. Introduction to natural water chemistry. Marcel Dekher, Inc. 
New York, New York, USA. 
Pais, I., and J. B. Jones. 1997. The hand book of trace elements. St. Lucie Press, Boca 
Raton, Florida, USA.  
Roy, L. A., D. A. Davis, I. P. Saoud, C. A. Boyd,  H. J. Pine, and C. E. Boyd. 2010. 
Shrimp culture in inland low salinity waters. Reviews in Aquaculture 2: 191-
208. 
Schindler, P. W. 1967. Heterogenous equilibria involving oxides, hydroxides, 
carbonates, and hydroxide carbonates.  Pages 196-221 in R. F. Gould (ed.), 
61 
 
 
 
 
Equilibrium  concepts in natural water systems.  Advances in Chemistry Series 
67, American Chemical Society, Washington, D.C., USA. 
Tucker, C. S. 1996. The ecology of channel catfish ponds in nortwest Mississippi. 
Reviews in Fisheres Science 4: 1-55. 
United States Environmental Protection Agency. 1976. Quality criteria for water. 
Environmental Protection Agency, Washington, D.C., USA. 
United States Environmental Protection Agency. 1994. Determination of trace 
elements in waters and wastes by inductively coupled plasma ? mass 
spectrometry, EPA Method 200.8 (Revision 5.4). 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
62 
 
 
 
 
Table 1.  Data on pond area and depth, stocking date and postlarval (PL) density, aeration 
rate, and amount feed applied for seven ponds at Farm A,an inland, low-salinity shrimp 
farm in Alabama. 
 
 
 
 
 
 
 
 
 
 
 
 
Pond Area (ha) Average Depth (m) Stocking data 
Aeration 
Rate 
(hp/ha) 
Feed 
Applied 
(kg/ha) Date PLs/m2 
N-2 0.57 1.64 May 7, 2009 28.2 8.8 7,158  
N-4 1.21 1.62 May 7, 2009 26.0 10.7 8,212  
N-6 1.50 1.60 May 7, 2009 27.0 8.7 6,947  
N-8 1.54 1.76 Apr 28, 2009 23.9 9.8 6,329  
S-1 1.17 1.26 May 7, 2009 15.0 8.5 4,967  
S-6 1.42 1.63 Apr 24, 2009 20.9 9.2 5,724  
S-8 1.94 1.57 Apr 24, 2009 22.6 11.8 8,688  
63 
 
 
 
 
Table 2.  Dry weight concentrations of trace elements in shrimp and feed, grand means, 
standard deviations (SD), ranges and coefficients of variation (CV) for trace element 
concentrations for waters of ten ponds at inland, low-salinity shrimp farms in Alabama.  
Correlation coefficients (r) between feed inputs of trace elements (X variable) and 
concentrations of these elements in waters of seven ponds on one farm also are shown. 
 
1ND = not detectable ( < 0.1 ?g/L). 
 
Element Shrimp 
(mg/kg) 
Feed 
(mg/kg) 
Pond water 
r Grand Mean 
? SD ( ?g/L) 
Range 
( ?g/L) 
CV 
(%) 
Aluminum 244 261 704 ? 732 137-3,007 104.0 0.302 
Arsenic 1.3 ND1 2.5 ? 3.01 ND-13.0 120.4 --- 
Barium 45 7.6 145 ? 133 20-710 91.7 -0.389 
Boron 50 7.4 687 ? 192 248-1,063 27.9 -0.463 
Cadmium ND 0.6 ND --- --- --- 
Chromium 1.2 1.2 2.1 ? 2.6 ND-15 123.8 0.352 
Cobalt 0.2 30.6 1.4 ? 2.8 ND-17 200.0 0.290 
Copper 62 10.6 5.9 ? 13.0 1.9-77 220.3 0.264 
Lead ND ND 2.3 ? 3.5 1.1-18 152.2 -0.257 
Iron 145 242 479 ? 596 1.5-3,060 124.4  0.316 
Manganese 31 87 24 ? 73 ND-380 304.2 -0.017 
Molybdenum ND 1.6 2.2 ? 1.9 ND-10 86.4 -0.521 
Nickel 1.4 4.1 4.2 ? 2.6 ND-14 61.9  -0.205 
Selenium 1.0 ND 5.4 ? 5.8 ND-22 107.4  -0.173 
Silicon ND 13.8 1,037 ? 1,214 97-5,501 117.1  0.383 
Titanium 7.3 ND 7.2 ? 6.0 ND-34 83.3   0.271 
Zinc 50 185 21.5 ? 8.7 11-62 40.5  0.045 
Zirconium ND ND 0.5 ? 2.0 ND-16 400.0  -0.645 
64 
 
 
 
 
Table 3.  Summary of safe concentrations of trace elements to aquatic life for long-term 
exposure.  Developed from data presented by Australian and New Zealand Council on 
Environmental Protection (1992), Boyd and Tucker (1998), and United States 
Environmental Protection Agency (1976). 
 
1NF = not found in literature. 
Element Maximum safe concentration (?g/L) Comments 
Aluminum 100 to 200 For pH < 6, but a higher concentration can be tolerated at greater pH. 
Arsenic 50  
Barium 1,000  
Boron NF1 Ocean water has 4,500 ?g/L uni2500 much more than found in study ponds. 
Cadmium 5  
Chromium 100  
Copper Alkalinity (mg/L) ? 2.5 The maximum safe concentration would be about 175 ?g/L in study ponds. 
Lead 60  
Iron 1,000  
Manganese 1,000  
Molybdenum 75  
Nickel 50  
Selenium 10  
Silicon NF1 
Ocean water has 3,000?g/L.  Only one 
sample in the study ponds exceeds this 
level.   
Titanium NF1 Not considered highly toxic. 
Zinc 50  
Zirconium NF1 Not considered highly toxic. 
65 
 
 
 
 
Table 4.  Harvest data, crop duration, survival, production, and feed conversion ratio 
(FCR) for seven ponds at Farm A,an inland, low-salinity shrimp farm in Alabama. 
 
 
 
 
 
 
 
 
 
 
 
 
Pond 
Harvest data Crop duration 
(Days) Survival 
Production 
(kg/ha) FCR Date Shrimp/m2 
N-2 Oct 15, 2009 9.2 161 32.9 3,005  2.38 
N-4 Oct 1, 2009 18.4 147 70.4 4,794  1.71 
N-6 Sep 23, 2009 25.7 139 95.4 5,425  1.28 
N-8 Oct 27, 2009 11.5 182 47.9 3,565  1.78 
S-1 Sep 28, 2009 12.6 144 84.0 3,722  1.33 
S-6 Sep 9, 2009 14.3 138 68.3 3,361  1.70 
S-8 Oct 22, 2009 19.2 181 84.7 4,767  1.82 
66 
 
 
 
 
Table 5.  Correlation coefficients between trace element concentrations in water (X 
variable) and shrimp survival, production, and feed conversion ratio (FCR) in inland 
shrimp ponds in Alabama.  Asterisks by entries denote significance at P < 0.05. 
 
1df = 5. 
2df = 8. 
 
 
 
 
   Element Water vs Water vs Water vs Survival1 Production2 FCR1 
Aluminum 0.327 0.308 -0.200 
Arsenic -0.239 0.604 -0.582 
Barium -0.318 -0.473 -0.126 
Boron -0.228 0.114 0.358 
Chromium 0.288 0.554 -0.045 
Cobalt  0.844*   0.755* -0.551 
Copper 0.063 -0.373 -0.141 
Lead   0.852* 0.370  -0.854* 
Iron 0.481  0.711* -0.361 
Manganese 0.530 0.377 -0.538 
Molybdenum -0.283 0.045 0.055 
Nickel 0.318 0.228 -0.513 
Selenium -0.114 -0.475 0.179 
Silicon 0.352 0.524 -0.182 
Titanium 0.152 0.469 -0.089 
Zinc   0.902*   0.673*   -0.802* 
Zirconium 0.293 0.055 -0.451 
67 
 
 
 
 
 
Fig. 1.Variation in concentrations of eight trace elements; cobalt, molybdenum, boron, 
iron, nickel, lead, copper, and zinc on each sampling date for pond N-8 at Farm A. 
 
 
 
 
 
  
  
0
2
4
6
8
M
ay
 6 20
Ju
n 3 18 Jul 1 14 28
Au
g 1
1 25
Se
p 0
8 22
Oc
t 6
ug/
L
Cobalt
Molybdenum
0
1000
2000
3000
M
ay
 6 20
Ju
n 3 18 Jul 1 14 28
Au
g 1
1 25
Se
p 0
8 22
Oc
t 6
Boron
Iron
0
2
4
6
8
10
M
ay
 6 20
Ju
n 3 18 Jul 1 14 28
Au
g 1
1 25
Se
p 0
8 22
Oc
t 6
ug/
L
Date
Nickel
Lead
0
10
20
30
40
M
ay
 6 20
Ju
n 3 18 Jul 1 14 28
Au
g 1
1 25
Se
p 0
8 22
Oc
t 6
Date
Copper
Zinc
68 
 
 
 
 
 
 
 
 
 
V.  Water Temperature in Inland, Low-Salinity Shrimp Ponds in Alabama 
 
Abstract 
 
 
Average, daily water temperature in low-salinity, inland shrimp ponds in Alabama 
was estimated closely by averaging minimum and maximum, daily water temperatures.  
There was a high correlation (P < 0.01) between mean, daily air and water temperatures; 
pond water usually averaged 3 to 4oC warmer than the air.  Monthly, mean water 
temperatures among eight ponds differed by 3.40oC in May and by 2.83oC in September, 
but there was less than 1oC difference among ponds in June, July, and August.  
Differences in temperature among ponds were not related to the pond water 
surface:volume ratio, but in July and September there was a negative correlation (P < 
0.05) with increasing aeration rate.  However, differences in water temperature among 
ponds probably were related mainly to variation in plankton density among ponds (a 
variable not measured in the study).  The negative correlations (P < 0.05) between 
average water temperature over the entire culture period in each pond and both shrimp 
survival and production are thought to have resulted from variation in crop duration and 
therefore are not causal.  Nevertheless, differences in water temperature among ponds in 
May and September were great enough to have possibly influenced shrimp survival and 
production. 
 
69 
 
 
 
 
Introduction 
 
 
Water temperature is an important variable in aquaculture; it influences growth 
rates of culture species as well as those of all other living things uni2500 both desirable and 
undesirable uni2500 in production systems (Stickney 2000).  Temperature also controls rates of 
physical processes and chemical reactions that impact environmental quality in culture 
systems (Boyd and Tucker 1998, Stumm and Morgan 1996).  Much is written about 
temperature preferences of individual species and of the effects of temperature on the 
culture milieu.  Aquaculture species are selected for a particular location based upon their 
temperature tolerances (Stickney 2000), the timing of stocking and harvesting is 
scheduled to avoid temperature limitations on survival and growth (Green and Popham 
2008, Stickney 2000), and temperature influences water quality management decisions 
(Boyd and Tucker 1998). 
Variation in temperature patterns among years has a major influence on fish and 
shrimp production in ponds (Boyd and Pine 2006), but little attention has been given to 
daily, monthly or seasonal variations in temperature among culture units that could 
possibly result from differences in depth, water quality conditions, and management 
inputs.  Heat is gained and lost through pond water surfaces, and the amount of heat that 
can be stored in a pond is a function of volume (Yoo and Boyd 1994).  In static ponds, 
heat gains and losses through inflows and outflows of water are minor, and the surface 
area:volume ratio might be an important factor influencing heat balance and water 
temperature. 
Suspended organic particles absorb heat, and these particles increase the rate of 
light quenching in water.  Thus, plankton blooms increase heat absorption in surface 
70 
 
 
 
 
water, while restricting the penetration of solar energy into deeper water (Idso and Foster 
1974).  Finally, mechanical aeration of aquaculture ponds increases the rate of vertical 
mixing of the water column to lessen thermal gradients, and the splashing action of 
aerators encourages evaporation and heat loss from ponds (Boyd and Pine 2006). 
The purpose of this study was to monitor water temperature in eight ponds on a 
shrimp farm to ascertain if differences in temperature could be detected among ponds of 
different surface area : volume ratios and mechanical aeration rates.  In addition, the 
possible contribution of water temperature to variation in shrimp survival and production 
among ponds was investigated. 
 
Materials and Methods 
 
 
The shrimp farm for this study is located in southeastern Greene County, 
Alabama on state Highway 43 about 5 km north of Forkland.  This farm has 17 ponds, 
eight of which were selected for this study (Table 1).  The ponds were selected to provide 
a range in water surface:volume ratio; they varied in water surface area from 0.57 ha to 
2.02 ha and from 1.16 m to 1.77 m in average depth.  The ponds are filled with water of 
about 4 ppt salinity from wells extended into a saline water aquifer.  Water exchange is 
not practiced on the farm, and storage volume to capture rainfall is provided by 
maintaining water levels 10 to 15 cm below the intake of overflow pipes (Boyd 1982, 
Cathcart et al. 1999).  In previous years, water has seldom been observed to overflow 
from ponds.  
Seven ponds were stocked on 11 May 2010, and the other one was stocked on 25 
May 2010 with 11.8 to 31.3 postlarvae/m2 (Table 1).  Aerators were installed at 8.5 to 
71 
 
 
 
 
12.8 hp/ha and operated mostly at night (Table 1).  A pelleted feed containing 35% crude 
protein was applied twice daily, and amounts used were recorded.  Shrimp were 
harvested between 8 September and 20 October 2010. 
A Model 64K HOBO Pendant Temperature Data Logger (HOBOware?, 
Janesville, Wisconsin, USA) was attached to the top of a concrete block (20 cm tall) and 
placed at 1 m depth in each study pond on 12 May 2010.  A Model HOBO 
Temp/External air temperature data logger was mounted in the shade at a height of 3 m 
under an open tractor shed uni2500 roof but no sides uni2500 located within 700 m of the most distant 
pond.  The temperature loggers were installed one day after the first ponds were stocked 
and left in ponds until harvest.  The recorders were programmed to monitor temperature 
at 2-h intervals.  At the end of the study, data from temperature loggers were downloaded 
into a lap-top computer using software provided by the manufacturer; HOBOware Pro 
and BoxCar Pro 4.3 for water temperature data logger and air temperature data logger, 
respectively. 
Mean, daily air and water temperatures were calculated two ways:  by averaging 
all 2-h reading each day; by averaging the daily maximum and minimum temperature.  
Monthly and culture period means (estimated from stocking to harvest) for each pond and 
the grand mean for all ponds were based on average of daily temperature data. 
 
Results and Discussion 
 
 
The range in daily, water temperature was fairly small as illustrated for Pond N-7 
(Fig. 1).  The difference in daily minimum and daily maximum temperatures averaged 
1.48 ? 1.82oC, and ranged from 0.19oC on 12 May to 2.77oC on 8 October.  The 
72 
 
 
 
 
relatively small differences between daily minimum and maximum water temperatures 
were the result of water mixing by mechanical aeration. 
The average, daily water temperature in ponds, calculated by either averaging all 
daily values or by averaging daily minimum and maximum values (Fig. 2), were nearly 
always slightly higher than average, daily air temperature as also illustrated with data 
from Pond N-7.  There was a high correlation between mean, daily water temperatures 
estimated by the two different methods of averaging (Fig. 3), and it was decided to work 
with the daily averages based on minimum and maximum values.  There also was an 
excellent correlation (P < 0.01) between average, daily air and water temperatures for 
Pond N-7 (Fig. 3). 
Average, daily water temperature in Pond N-7 (Fig. 2) was 25oC or more from 
stocking on 11 May [ordinal day (OD) 131] until 29 September (OD 272) ? a period of 
141 d.  Water temperature was 30oC or greater for 101 d ? 6 June (OD 157) to 24 
September (OD 267).  Between 23 July (OD 204) and 13 August (OD 225), water 
temperature often averaged between 34 and 35oC.  Average, daily water temperature 
diminished below 25oC after 29 September, and it fell to about 19oC on the day of harvest 
(20 October, OD 293). 
The range in average, daily water temperature among ponds was fairly large in 
May and June, but it was less later in the grow-out period as illustrated with data for one 
day in each month from May to September:  12 May, 23.63 to 27.03 oC; 12 June, 30.35 to 
32.20oC; 12 July, 32.10 to 32.61oC; 12 August, 33.20 to 34.23oC; 12 September, 30.76 to 
31.07oC.  Monthly averages for water temperature differed by 2.06oC among ponds in 
73 
 
 
 
 
May, by 0.51 to 0.68oC during the period June through August, and by 2.83oC in 
September.     
Culture period means for water temperature in the eight ponds ranged from 29.66 
to 31.56oC, and they were as follows : N-2, 31.56oC; N-4 31.07oC; N-5, 30.39oC; N-6, 
30.01oC; N-7, 29.66oC; N-8, 30.7oC; S-1, 30.06oC; and S-3, 30.97oC.  The grand mean 
was 30.51oC with a standard deviation of ?0.637oC.  These differences also were not 
correlated (P > 0.05) with either aeration rate or pond surface area:volume ratio (Fig. 4), 
but the correlations possibly were affected by the influence of low water temperatures in 
ponds harvested after OD 272 (29 September) on culture period means. 
Monthly averages for water temperatures in ponds were not correlated with pond 
surface water area:volume ratio either.  Differential heat absorption by waters caused by 
differences in turbidity, and particularly phytoplankton abundance, likely caused most of 
the variation in water temperature among ponds, but it was not possible to obtain 
estimates of either turbidity or phytoplankton abundance in this study.  There were, 
however, negative correlations between monthly water temperature and aeration rate for 
July (r = -0.667; P < 0.05) and September (r = -0.923; (P < 0.01). 
Data on shrimp performance provided by the farm manager after harvest varied as 
follows:  production, 2,267 to 6,516 kg/ha; crop duration, 106 to 162 days; survival 25.5 
to 79.3%; FCR, 1.38 to 4.11 (Table 3).  The manager overestimated survival rate in pond 
N-8 and applied excessive feed resulting in one high FCR. 
Production and survival appeared to decline as average culture period water 
temperature increased (Fig. 5), but only the correlation for production was significant.  
There was no correlation (P > 0.05) of water temperature with FCR even if the pond with 
74 
 
 
 
 
FCR = 4.11 (Pond N-8) is omitted (Fig. 5).  The data are complicated by two facts:  water 
temperature was negatively correlated with crop duration (Fig. 6) as a result of longer 
crops extending into the cooler fall days, by chance or intention, ponds with smaller 
production were harvested first.  Nevertheless, variation in daily and monthly, mean 
water temperatures among ponds were as much as 3.40oC and 2.44oC, respectively (in 
May) and 2.83oC and 2.72oC, respectively (in September).  Shrimp, like other 
aquaculture species, probably have a Q10 for growth of around 2 (Boyd and Tucker 
1998), and in May and September, the differences in water temperature among ponds 
probably influenced growth rate.  During June, July, and August, the small differences in 
water temperatures among ponds probably did not have much effect on growth.  Frequent 
estimates of growth rate ? a variable not available for ponds in this study ? would be 
needed to verify that monthly or shorter differences in water temperature among ponds 
influence shrimp production. 
 
 
 
 
 
 
 
 
 
 
75 
 
 
 
 
Literature cited 
 
 
Boyd, C. E. 1982. Hydrology of small experimental fish ponds at Auburn, Alabama. 
Transactions of the American Fisheris Society 111: 638-644. 
Boyd, C. E. and C. S. Tucker. 1998. Pond aquaculture water quality management. 
Kluwer Academic Publishers, Boston, Massachusetts.700 p. 
Boyd, C. E. and H. J. Pine. 2006. Application of agrometerology to aquaculture and 
fisheries, chapter 14. In: WMO/CAgM Guide to Agricultural Meteorological 
Practices (GAMP). Published online:http://www.agrometeorology.org/files-
folder/repository/gamp_chapt14final.pdf. 
Cathcart, T. P., J. W. Pote, and D. W. Rutherford. 1999. Reduciton of effluent 
discharge and ground water use in catfish ponds. Aquacultural Engineering 20: 
163-174. 
Green, B. W. and T. W. Popham. 2008. Probabilities of low nighttime temperatures 
during stocking and harvest seasons for inland shrimp culture. Journal of the 
World Aquaculture Society 39: 91-103. 
Idso, S. B. and J. M. Foster 1974. Light and temperature relations in a small desert pond 
as influenced by phytoplanktonic density variations. Water Resources Research 
10: 129-132. 
Stickney, R. R. 2000. Temperature. , pages 923-934 In: R. R. Stickney, editor. 
Encyclopedia of Aquaculture, John Wiley & Son, Inc. New York, New York, 
USA. 
76 
 
 
 
 
Stumm, W. and J. J. Mogan. 1996. Aquatic chemistry, chemical equilibria and rates in 
natural waters. 3rd ed. John Wiley & Sons, Inc., New York, New York, USA: 
1022 p. 
Yoo, K. H. and C. E. Boyd. 1994. Hydrology and water supply for pond aquaculture. 
Chapman and Hall, New York, USA. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
77 
 
 
 
 
Table 1.  Pond areas and depths, stocking dates, aeration rates, and amounts of feed 
applied to eight study ponds at an inland, low-salinity shrimp farm in Alabama. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Pond Area (m2) Average Depth (m)  Stocking data  Aeration rate (hp/ha) Feed applied (kg/ha) Date PLs/m2 
N-2 5,666 1.32 25 May 31.3 8.8 3,603 
N-4 12,141 1.43 11 May 22.7 10.7 4,432 
N-5 13,335 1.22 11 May 29.2 9.7 8,939 
N-6 14,973 1.34 11 May 29.9 8.7 10,454 
N-7 20,234 1.77 11 May 29.0 11.4 11,152 
N-8 15,378 1.43 11 May 28.9 9.8 9,323 
S-1 11,736 1.16 11 May 29.6 8.5 8,438 
S-3 10,117 1.19 11 May 11.8 12.8 4,108 
78 
 
 
 
 
Table 2.  Production, crop duration, survival rates, and feed conversion ratio (FCR) for 
eight ponds at an inland, low-salinity shrimp farm in Alabama. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Pond 
Harvest 
date 
Production 
(kg/ha) 
Crop duration 
(days) 
Survival 
(%) 
 
FCR 
N-2 8 Sep 2,613 106 25.6 1.38 
N-4 15 Sep 2,993 127 44.9 1.48 
N-5 3 Oct 5,055 145 57.1 1.77 
N-6 18 Oct 6,516 160 79.2 1.60 
N-7 20 Oct 4,914 162 61.9 2.27 
N-8 11 Oct 2,267 153 29.8 4.11 
S-1 14 Oct 6,071 156 73.8 1.39 
S-3 28 Sep 2,607 140 58.5 1.58 
79 
 
 
 
 
Table 3.  Monthly, average water temperature for eight ponds at an inland, low-salinity 
shrimp farm in Alabama.  The letter H designated that ponds were harvested in 
September and could not be used in the average. 
 
 
 
Month N-2 N-4 N-5 N-6 N-7 N-8 S-1 S-3 
         May 26.68 27.81 26.30 27.93 27.15 28.74 28.25 28.05 
June 31.77 32.08 31.84 32.07 31.62 32.20 31.63 31.81 
July 32.10 31.88 32.10 32.36 32.13 32.09 32.39 31.99 
August 32.05 31.89 31.77 32.36 32.27 31.99 32.02 32.12 
September H H 28.58 29.49 26.30 29.02 29.13 H 
 
 
 
Fig. 1.  Daily minimum and maximum water temperature in Pond N-7 at an inland, low-salinity shrimp farm in Alabama. 
 
 
0
5
10
15
20
25
30
35
40
132 142 152 162 172 182 192 202 212 222 232 242 252 262 272 282
Wat
e r  
t e m
p e
r at
u r
e  (
o C
)
Ordinal date
Maximum
Minimum
80
 
 
 
 
 
Fig. 2.  Mean daily, air temperatures and water temperatures in Pond N-7 at an inland, low-salinity shrimp farm in Alabama. 
0
5
10
15
20
25
30
35
40
132 142 152 162 172 182 192 202 212 222 232 242 252 262 272 282
T e
r m
p e
r at
u r
e  (
o C
)
Ordinal date
Average of daily minimum and maximum temperature
Air
N-7
0
5
10
15
20
25
30
35
40
132 142 152 162 172 182 192 202 212 222 232 242 252 262 272 282
T e
m p
e r at
u r
e  (
o C
)
Ordinal date
Average of 2-hr reading for each day
Air
N-7
  8
1 
82 
 
 
 
 
 
Fig. 3.  Left: Relationship between average, daily air temperatures and water 
temperatures in Pond N-7 at an inland, low-salinity shrimp farm in Alabama. Right: 
Relationship between average, daily water temperatures averaged by two methods: 
average of 2-h reading and minimum-maximum temperature averaging. 
 
 
 
 
 
 
 
 
y = 0.8253x + 7.4916
r = 0.9177
P < 0.01
0
5
10
15
20
25
30
35
40
0 10 20 30 40
Wat
er 
ter
mp
erat
ur
e (
o C
)
Air temperature (oC)
y = 0.9994x - 0.0049
r = 0.9996
P < 0.01
0
5
10
15
20
25
30
35
40
0 10 20 30 40
Wa
ter
 te
mp
era
tur
e (
o C
), A
ve
ra
ge
 of
 2-
h r
ea
din
gs 
Water temperature (oC), Mininum-
maximum average 
83 
 
 
 
 
 
    
    
    
W
ate
r t
em
pe
ra
tur
e (
o C
) 
Fig. 4.  Relationship between aeration rate and pond surface area/volume ratio to average, 
and average, crop-period water temperatures in eight ponds at an inland, low-salinity 
shrimp farm in Alabama. 
 
 
 
 
 
 
 
 
 
 
29
30
31
32
6 8 10 12 14 16
Aeration rate (hp/ha)
r = 0.097
P > 0.05
29
30
31
32
0.5 0.6 0.7 0.8 0.9
Surface area/volume
r = 0.297
P > 0.05
84 
 
 
 
 
 
 
 
 
 
               Mean water temperature (oC)         Mean water temperature (oC) 
 
Fig. 5.  Relationships between average, crop-period water temperature and shrimp 
production variables in eight ponds at an inland, low-salinity shrimp farm in Alabama. 
 
0
2,000
4,000
6,000
8,000
29 30 31 32
Pr
od
uc
tion
 (k
g/h
a)
r = 0.725
P < 0.05
0
25
50
75
100
29 30 31 32
Su
rvi
val
 (%
)
r = 0.676
P > 0.05
0
1
2
3
4
5
29 30 31 32
FC
R
with N-8
r = 0.282
P > 0.05
0
1
2
3
29 30 31 32
FC
R
without N-8
r = 0.636
P > 0.05
85 
 
 
 
 
 
 
 
Fig. 6.  Relationship of crop duration to average, crop-period temperature in eight ponds 
at an inland, low-salinity shrimp farm in Alabama. 
 
 
 
 
 
 
 
 
 
 
 
29
30
31
32
100 120 140 160 180
Wa
ter
 te
mp
era
tur
e (
o C
)
Crop duration (days)
r = 0.955
P < 0.01
86 
 
 
 
 
 
 
 
 
 
VI.  Effluent Volume and Pollutant Loads at an Inland, Low-Salinity Shrimp Farm  
in Alabama 
 
Abstract 
 
 
An inland, low-salinity shrimp farm in Alabama did not release effluent during 
the grow-out period, but draining effluent at harvest included 50.4% and 57.9% of 
impounded water in 2008 and 2010, respectively.  Maximum concentrations of water 
quality values in draining effluent were:  total suspended solids, 627 mg/L; settleable 
solids, 11 ml/L; turbidity, 448 NTU; total phosphorus, 1.15 mg/L; total nitrogen, 11.5 
mg/L; 5-d biochemical oxygen demand, 33.5 mg/L; chloride, 2,450 mg/L; and pH, 8.1.  
Weighted concentrations of these variables were considerably lower ? except for pH 
which was about the same.  Farm effluent caused a marked increase in concentrations of 
all variables other than pH at a sampling station about 500 m downstream of the farm 
outfall.  But only chloride concentration exceeded concentrations allowed in Alabama 
streams classified for fish and wildlife propagation.  Average pollutant discharge per 
tonne of shrimp was 444.9 kg total suspended solids, 51.3 kg 5-d biochemical oxygen 
demand, 15.2 kg total nitrogen, 1.33 kg total phosphorus, and 4,402 kg chloride.  
Concentrations of turbidity, settleable solids, total suspended solids, total phosphorus and 
possibly other variables in effluent could be lessened by installation of a settling basin to 
remove medium and coarse solids before final discharge.  Release of less water from the 
87 
 
 
 
 
farm during harvest, and improvement in feed conversion ratio ? which was 1.52 in 2008 
and 1.86 in 2010 ? also would lessen pollutant loads per tonne of shrimp. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
88 
 
 
 
 
Introduction 
 
 
Inland culture of marine shrimp in low-salinity water is a new method of shrimp 
production that is increasing in importance (Roy et al. 2010).  In Alabama, low-salinity 
water (2 to 10 ppt) for inland shrimp culture is pumped from a saline aquifer.  This water 
has low concentrations of potassium and magnesium, and it must be treated with 
potassium and magnesium fertilizers to counteract cation imbalances that negatively 
affect shrimp survival and growth (Boyd et al. 2007, McNevin et al. 2004, Pine and Boyd 
2010).  Water exchange is not used, and farmers attempt to reduce discharge during 
harvest in order to lessen pumping costs to refill pond and to conserve potassium and 
magnesium applied in fertilizers. 
The major environmental concern about inland shrimp farming has been possible 
salination of streams, aquifers, and soils by discharge from ponds (Boyd et al. 2006, 
Braaten and Flaherty 2001, Pine and Boyd 2010, Roy et al. 2010).  In other types of pond 
aquaculture, there is concern about the discharge of nutrients, organic matter, and 
suspended solids that could cause eutrophication and sedimentation in receiving water 
bodies.  This issue has not been raised for inland shrimp farms, apparently because the 
potential for salination is obvious and efforts to reduce salt discharge also would lessen 
release of other pollutants. 
The purpose of this study was to evaluate effluent volume and pollutant loads at a 
low-salinity, inland shrimp farm in Alabama. 
 
 
 
 
89 
 
 
 
 
Materials and Methods 
 
 
Farm and management 
 
The study was conducted during two annual grow-out cycles ? 2008 and 2010 ? at 
a shrimp farm in southeastern Greene County, Alabama about 5 km north of Forkland on 
state Highway 43.  This farm has 17 ponds (Fig. 1) ranging from 0.49 to 2.02 ha in ?full-
pond? water surface area for a total of 21.77 ha.  Average full depths vary from 1.26 m to 
2.07 m (average = 1.58 m).  The total water volume for the farm is 340,079 m3.  
Ponds were completely filled with saline ground water (~ 4 ppt) from two wells in 
March and April each year.  Fertilizer grade potassium chloride or muriate of potash 
(~50% K) and potassium magnesium sulfate or KMag? (Mosaic Company, Plymouth, 
Minnesota, USA) (17.8% K and 10.5% Mg) were applied to ponds to raise potassium 
concentration to 50 mg/L and magnesium concentration to 30 mg/L as is common 
practice in Alabama inland shrimp culture (Boyd et al. 2007, McNevin et al. 2004, Pine 
and Boyd 2010).  Pacific white shrimp L. vannamei from Harlingen shrimp farm, Los 
Fresnos, Texas  and from Shrimp Improvement Systems, Islamorada, Florida were 
stocked at an average density of 24 postlarvae/m2 between  late April and early June in 
2008 and with an average 27 postlarvae/m2 between late April and late May in 2010.  
Shrimp were fed twice daily with a commercial, pelleted feed containing 35 % crude 
protein.  One or two, 10-hp electric, paddlewheel aerators were installed in each pond and 
one, 3-hp Aire-O2? aerator was also installed in 10 ponds.  The average, aerator power 
rate was 10.9 hp/ha (range of 6.2 to 23.7 hp/ha).  Aerators were operated mostly during 
nighttime. 
90 
 
 
 
 
Water levels in ponds were 2 to 10 cm below tops of overflow pipes when shrimp 
were stocked, and water was pumped into ponds as needed to replace seepage and 
evaporation and maintain water levels 10 to 15 cm below tops of drains.  This water-level 
management technique is called the ?drop-fill? method, and it provides storage capacity 
for rainfall thereby preventing overflow after normal rainfall events (Boyd 1982, Cathcart 
et al. 1999).  Water was not observed to overflow from ponds during the production 
period either year. 
Shrimp were harvested during September and October both years.  At harvest, 
water was discharged from ponds into Needham creek (Fig. 1), or it was pumped into 
adjacent ponds for reuse. 
 
Water volume 
 
Ponds have embankments with 2:1 (horizontal to vertical) side slopes around the 
area in which water is stored.  Bottoms slope towards drains to facilitate draining at 
harvest, but until water levels drop about 1.2 m below tops of overflow pipes, water 
surfaces are above toes of embankments even on the shallow-most sides of ponds.  The 
manager agreed to manage draining so that at completion ponds would either be 
completely empty or have water levels not more than 1.0 m below tops of overflow pipes. 
The vertical distance of the water level below the top of the overflow pipe was 
measured in each pond when drawdown for harvest was initiated.  On the day after the 
final pond was harvested, empty ponds were identified and vertical distances of water 
levels below tops of the overflow pipes were measured in the other ponds.  The volume 
of water discharged for individual ponds was calculated as follows: 
91 
 
 
 
 
Ponds empty after harvest: 
 VD  =  [H ? ?h] b [A ? (2L x ?h)]b 
Ponds with water after harvest: 
 VD  =  [[H ? ?h][A ? (2L x ?h)]]b ? [[H ? ?h][A ? (2L x ?h)]] a 
where VD   =   volume of discharge (m3); H = average full pond depth (m); ?h = distance 
from water level to top of overflow pipe (m); A = full pond water surface 
area (m2); L = shoreline length at full pond water level (m), a and b = 
after and before draining for harvest, respectively. 
Discharge volumes of all ponds were summed to estimate total farm discharge. 
 
Sampling and analyses 
 
Water samples were collected from four selected ponds during drawdown for 
harvest both years.  Samples were collected before initiating drawdown, and when 
drawdown was estimated to be 50%, 75%, 95%, and 99% complete.  Water samples were 
put into 2-L plastic bottles, stored in insulated ice chests, and transported to Auburn 
University for analyses.  Analyses were made according to methodology recommended 
by Eaton et al. (2005) as follows: pH (glass electrode); settleable solids (Imhoff cone); 
total suspended solids (TSS, glass fiber filtration followed by gravimetry); turbidity 
(nephelometer); biochemical oxygen demand (standard, 5-d test, BOD5); chloride 
(diphenylcarbazone method).  Samples for total nitrogen and total phosphorus were 
subjected to persulfate digestion (Eaton et al. 2005), and nitrate and orthophosphate in 
digestates were measured by the ultraviolet spectrophotometric screening method (Eaton 
92 
 
 
 
 
et al. 2005, Gross et al.1999) and ascorbic acid methods, respectively (Gross and Boyd 
1998 ). 
The weighted average for each water quality variable was calculated using the 
following equation: 
XW  =  [(X100 + X50)/2] 0.5 + [(X50 + X25)/2] 0.25 +  
                        [(X25 + X5)/2] 0.2 + [(X5 + X0)/2] 0.05  
where XW    =  weighted average for variable X (g/m3); subscripts 0 to100 = stage of 
drawdown when water sample collected, e.g., 25% of water remained in 
pond when sample X25 was taken; decimal fractions = proportion of water 
discharged between two sampling times. 
The discharge of pollutants per tonne of shrimp production each year was 
calculated as follows: 
PLX       =      (XW)(VD)(10-3) 
                             S 
where PLX  =  pollution load of variable X (kg/tonne shrimp); XW = weighted average for 
variable X (g/m3); VD = farm discharge (m3); 10-3 = kg/g; S = farm shrimp 
production (tonne). 
Three feed samples and three shrimp samples were collected, dried by 
lyophilization and pulverized to 40-mesh.  Nitrogen concentration was measured with a 
Leco CHN analyzer (Leco Corporation, Algonquin, Illinois, USA).  Aliquots of samples 
were digested in perchloric acid (Boyd and Teichert-Coddington 1995b), and phosphorus 
concentration was measured with a SpectroCirosCCD, induced coupled plasma 
93 
 
 
 
 
spectrophotometry (SPECTRO Analytical Instruments, Inc., Mahwah, New Jersey, 
USA).  
 
Results 
 
 
Total discharge from the farm was 154,826 m3 in 2008 and 174,931 m3 in 2010.  
The total volume of water on the farm at the beginning of harvest was 306,987 m3 and 
302,360 m3 in 2008 and 2010, respectively.  Thus, a greater percentage of pond water 
was discharged for harvesting ponds in 2010 (57.9%) than in 2008 (50.4%). 
During draining for harvest, concentrations of pH and chloride remained fairly 
constant during drawdown, but concentrations of other variables tended to increase as 
drawdown progressed and especially in the final 25% of the effluent as illustrated for data 
collected in 2008 (Fig. 2).  This pattern of change in concentrations of water quality 
variables in effluent is typically observed when ponds are drained for harvest (Boyd 
1978, Schwartz and Boyd 1994b, Teichert-Coddington et al. 1999).  The data were used 
to estimate weighted averages for concentrations of variables in draining effluent (Table 
1) that were similar for both years.  The effluent caused concentrations of all water 
quality variables other than pH in the receiving stream to increase downstream of the 
farm outfall (Table 2). 
Feed use and shrimp production on the farm were 118,132 kg and 77,809 kg, 
respectively, in 2008 and 154,201 kg and 82,697 kg, respectively, in 2010.  Thus, the 
farm feed conversion ratio (FCR) was 1.52 in 2008 and 1.86 in 2010. 
94 
 
 
 
 
The nitrogen and phosphorus concentrations in shrimp were 2.75% and 0.25% of 
live weight, respectively.  The air dry feed contained 6.08% nitrogen and 1.2% 
phosphorus. 
 
Discussion 
 
 
The United States Environmental Protection Agency (USEPA) aquaculture rule 
(Federal Register 2004) defined warmwater concentrated aquatic animal production 
(CAAP) facilities as ponds, raceways, or other production units that produce over 45,455 
harvest kilograms per year but excluded facilities that discharge less than 30 d/yr except 
for excess runoff.  The farm is a CAAP facility because it produced over 45,455 kg of 
shrimp each year, and because ponds were drained over 44-d period in 2008 and a 46-d 
period in 2010, resulting in more than 30-d of discharge both years.  The EPA rule 
requires that CAAP facilities obtain a National Pollutant Discharge Elimination System 
(NPDES) permit.  But, the rule does not impose effluent limitation guidelines.  Rather, it 
recommends the use of best management practices to lessen the volume and pollutional 
strength of effluent.  Thus, there are no specific aquaculture effluent standards against 
which to compare the effluent quality from the inland shrimp farm. 
Water quality standards of the Alabama stream classification system for stream 
classified for fish and wildlife propagation limits turbidity to 75 NTU, prohibits dissolved 
oxygen concentration > 5 mg/L, and requires pH to be between 6 and 8.5 (Boyd 2000).  
Shrimp pond effluent usually had greater turbidity than allowed by the stream standard, 
but effluent pH was within an acceptable range.  Dissolved oxygen concentrations were 
not measured in the samples, but the shrimp farm monitored dissolved oxygen in the 
95 
 
 
 
 
ponds during drawdown and reported that it did not fall below 5 mg/L.  The BOD5 and 
TSS limits typically allowed in NPDES permits for municipalities and industries range 
from 20 to 30 mg/L (Boyd and Gross 1999, Carter 1984).  The shrimp pond effluent often 
exceeded these limits.  
The Alabama Department of Environmental Management adopted the 
recommendation of Benoit (1988) that effluent should not cause in-stream chloride 
concentration to rise above 230 mg/L.  The shrimp farm effluent was much higher than 
the in-stream chloride standard.  Standards for nitrogen and phosphorus seldom are 
included in NPDES permits in the southeastern United States (Schwartz and Boyd 
1994a).  Although shrimp pond effluent exceeded limits for some variables typically 
included in NPDES permits, they were relatively dilute with respect to effluents from 
industrial and municipal sources.  For example, according to Tchobanoglous et al. (2003), 
untreated municipal sewage contains 20 to 70 mg/L total nitrogen, 4 to 12 mg/L total 
phosphorus, 110 to 350 mg/L BOD5, and 120 to 400 mg/L TSS. 
The input of nitrogen in feed was 8,798 kg in 2008 and 9,374 kg in 2010; the 
corresponding input of phosphorus was 1,736 kg in 2008 and 1,850 kg in 2010.  Shrimp 
harvest removed 2,140 kg nitrogen and 194 kg phosphorus in 2008 and 2,274 kg nitrogen 
and 207 kg phosphorus in 2010.  Thus, the loads of nitrogen and phosphorus to the ponds 
were 6,658 kg nitrogen and 1,542 kg phosphorus in 2008 and 7,104 kg nitrogen and 
1,643 kg phosphorus in 2010.  However, the effluent loads of nitrogen and phosphorus 
(Table 1) were much lower.  Of the nitrogen applied in feed and not recovered in shrimp, 
effluent contained only 16.2% in 2008 and 18.5% in 2010; corresponding values for 
phosphorus were 5.0% in 2008 and 7.3% in 2010.  Thus, the ponds were quite effective 
96 
 
 
 
 
in removing nitrogen and phosphorus.  Nitrogen was lost through ammonia volatilization, 
denitrification, and in organic matter that settled to pond bottoms (Gross et al. 1999, 
2000).  The main loss of phosphorus was precipitation from the pond water as calcium 
phosphate and adsorption by bottom soils (Gross et al. 1998). 
The amounts of selected pollutants discharged per tonne of shrimp produced 
(Table 2) ? except for BOD5 ? were fairly similar both years.  The BOD5 in aquaculture 
ponds results primarily from phytoplankton (Boyd and Gross 1999), and phytoplankton 
density must have been greater in 2010 than in 2008.  The large discharge of chloride per 
tonne of shrimp is in agreement with findings of Boyd et al. (2006), and it is of particular 
concern, because ponds discharge into a freshwater stream. 
The high chloride concentration at the upstream site in the creek (Table 3) 
apparently was the result of drought conditions during 2008.  The period 2003 to 2006 
had more rainfall, and chloride concentration at the upstream site was below 100 mg/L 
during that 4-year period (Boyd et al. 2006).  Nevertheless, during shrimp harvest in 
2008, chloride concentration at the station downstream of the farm outfall was much 
greater than the concentration at the upstream station.  Of course, data collected during 
the years with more rainfall (Boyd et al. 2006) also revealed that chloride concentration 
increased in the stream below the farm outfall during the period of shrimp harvest and 
exceeded the in stream standard of 230 mg/L. 
Concentrations of total suspended solids, turbidity, total phosphorus, total 
nitrogen, and BOD5 also were elevated at the downstream station relatively to the 
upstream station.  However, the concentrations of these variables in the stream were not 
97 
 
 
 
 
in excess of concentrations allowed in Alabama streams classified for fish and wildlife 
propagation (Boyd 2000). 
Suspended solids concentration and turbidity in effluent could be lessened by 
sedimentation.  Ideally, a sedimentation basin should be constructed in the ditch that 
conveys water from the farm to the creek.  Alternatively, it might be possible to schedule 
pond draining so that one of the lower ponds is harvested first and this pond could then 
serve as a sedimentation basin.  There are two problems related to the alternative:  the 
water would have to be pumped from the lower pond to ponds at higher elevation at 
considerable expense; the lower pond would gradually filled with sediment making it less 
useful for shrimp production. 
Sedimentation also would reduce the total phosphorus concentration in effluent, 
because much of the phosphorus in pond water is associated with suspended soil particles 
(Boyd 2000).  However, sedimentation would not have much effect on the concentrations 
of total nitrogen, BOD5, or chloride.  The chloride concentration seems to be the variable 
of most concern with respect to water quality in the stream.  The practice that would be of 
most benefit in protecting water quality in the receiving stream would be to discharge less 
water at harvest.  This should be possible by transferring more water to adjacent ponds 
and storing it rather than releasing it during harvest.  Of course, more emphasis should be 
devoted to feed management, because the FCRs of 1.52 in 2008 and 1.86 in 2010 are 
higher than often achieved in P. vannamei culture (Shrimp Aquaculture Dialogue 2010).  
Reducing the FCR would lessen the amount of nitrogen and phosphorus discharged per 
tonne of shrimp produced. 
 
98 
 
 
 
 
Literature Cited 
 
 
Benoit, D. A. 1988. Ambient water quality criteria for chloride - 1988. EPA 440/5-88-
001. US Environmental Protection Agency, Washington, DC, USA. 
Boyd, C. A., C. E. Boyd, A. A. McNevin, and D. B. Rouse. 2006. Salt discharge from 
an inland farm for marine shrimp in Alabama. Journal of the World Aquaculture 
Society 37: 345-355. 
Boyd, C. A., C. E. Boyd, and D. B. Rouse. 2007. Potassium budget for inland, saline 
water shrimp ponds in Alabama. Aquacultural Engineering 36: 45-50. 
Boyd, C. E. 1982. Hydrology of small experimental fish ponds at Auburn, Alabama. 
Transactions of the American Fisheris Society 111: 638-644. 
Boyd, C. E. 2000. Water quality: an introduction. Kluwer Academic Publishers, 
Boston/Massachusetts, USA. 
Boyd, C. E. and A. Gross. 1999. Biochemical oxygen demand in channel catfish 
Ictalurus punctatus pond waters. Journal of the World Aquaculture Society 30: 
349-356. 
Boyd, C. E. and D. R. Teichert-Coddington. 1978. Effluents from catfish ponds during 
fish harvest. Journal of Environmental Quality 7: 59-63. 
Boyd, C. E. and D. R. Teichert-Coddington. 1995. Dry matter, ash, and elemental 
composition of pond-cultured Penaeus vannamei and P. stylirostis. Journal of the 
World Aquaculture Society 26: 88-92. 
Braaten, R. O. and M. Flaherty. 2001. Salt balances of inland shrimp ponds in 
Thailand: implications for land and water salinization. Environmental 
Conservation 28: 357-367. 
99 
 
 
 
 
Carter, K. B. 1984. 30/30 hindsight. Water pollution control Federation 56: 301-305. 
Cathcart, T. P., J. W. Pote, and D. W. Rutherford. 1999. Reduction of effluent 
discharge and ground water use in catfish ponds. Aquacultural Engineering 20: 
163-174. 
Eaton, A. D., L. S. Clesceri, E. W. Rice, and A. E. Greenberg. 2005. Standard 
methods for the examination of water and wastewater, 21st edition. American 
Public Health Association, Washington, D.C. 
Federal Register. 2004. Effluent limitations guidelines and new source performance 
standards for the concentrated aquatic animal production point source category: 
final rule. United States Federal Register 69: 51892-51930. 
Gross, A., and C. E. Boyd. 1998. A digestion procedure for the simultaneous 
determination of total nitrogen and total phosphorus in pond water. Journal of the 
World Aquaculture Society 29: 300-303. 
Gross, A., C. E. Boyd, and J. Seo. 1999. Evaluation of the ultraviolet 
spectrophotometric method for the measurement of total nitrogen in water. 
Journal of the World Aquaculture Society 30: 388-393. 
Gross, A., C. E. Boyd, and C. W. Wood. 1999. Ammonia volatilization from freshwater 
ponds. Journal of Environmental Quality 28: 793-797. 
Gross, A., C. E. Boyd, and C. W. Wood. 2000. Nitrogen transformations and balance in 
channel catfish ponds. Aquacultural Engineering 24: 1-14. 
Gross, A., C. E. Boyd, and R. T. Lovell. 1998. Phosphorus budgets for channel catfish 
ponds receiving diets with different phosphorus concentrations. Journal of the 
World Aquaculture Society 29: 31-39. 
100 
 
 
 
 
McNevin, A. A., C. E. Boyd, O. Silapajarn, and K. Silapajarn. 2004. Ionic 
supplementation of pond waters for inland culture of marine shrimp. Journal of 
the World Aquaculture Society 35: 460-467. 
Pine, H. J. and C. E. Boyd. 2010. Adsorption of magnesium by bottom soils in inland 
brackishwater shrimp ponds in Alabama. Journal of the World Aquaculture 
Society 41: 603-609. 
Roy, L. A., D. A. Davis, I. P. Saoud, C. A. Boyd,  H. J. Pine, and C. E. Boyd. 2010. 
Shrimp culture in inland low salinity waters. Reviews in Aquaculture 2: 191-208. 
Schwartz, M. F. and C. E. Boyd. 1994a. Channel catfish pond effluents. Progressive 
Fish-Culturist 56: 273-281. 
Schwartz, M. F. and C. E. Boyd. 1994b. Effluent quality during harvest orf channel 
catfish from watershed ponds. Progressive Fish-Culturist 56: 25-32. 
Shrimp Aquaculture Dialogue. 2010. Draft standards for responsible shrimp 
aquaculture. World Wildlife Fund, Washington, D.C., USA.online: 
(www.worldwildlife.org/what/globalmarkets/aquaculture/dialogues-shrimp.html). 
Tchobanoglous, G., F. L. Burton, and H. D. Stensel. 2003. Wastewater engineering. 
McGraw Hill, New York, New York. 
Teichert-Coddington, D. R., D. B. Rouse, A. Potts, and C. E. Boyd. 1999. Treatment 
of harvest discharge from intensive shrimp ponds by settling. Aquacultural 
Engineering 19: 147-161. 
 
 
 
101 
 
 
 
 
Table 1.  Weighted means (g1876g1191) ? standard errors (SE) and  for concentrations of selected 
water quality variables in draining effluent from four ponds on an inland, low-salinity 
shrimp farm in Alabama in 2008 and 2010. 
Variable 2008  2010 
g1876g1191?SE Range  g1876g1191?SE Range 
pH 7.75 ? 0.24 7.02 - 8.32  7.58 ? 0.08 7.32 - 7.81 
Settleable solids (mg/L) 3.00 ? 3.04 0.05 - 25.00  4.47 ? 3.15 0.01 - 18.50 
Total suspended solids (mg/L) 207 ? 32 40 - 672  225 ?68 56 - 943 
Turbidity (NTU) 174 ? 94 27 - 788  232 ?101 46 - 655 
BOD5 (mg/L) 19.5 ? 4.3 8.4 - 54.8  29.9 ?8.1 11.3 - 79.9 
Total nitrogen (mg/L) 6.95 ? 0.86 4.41 -14.70  7.52 ?1.02 4.06 - 16.28 
Total phosphorus (mg/L) 0.50 ? 0.09 0.23 - 1.68  0.69 ?0.09 0.26 - 1.55 
Chloride (mg/L) 2,279 ? 73 1,905 - 2,393  2,022 ?144   1,255 - 2,481 
 
 
 
 
 
 
 
 
 
 
 
 
102 
 
 
 
 
Table 2.  Total qualities of selected pollutants discharged and the amount of each 
pollutant per tonne of shrimp production in 2008 and 2010 at an inland, low-salinity 
shrimp farm in Alabama. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Variable 
2008  2010 
   (kg) (kg/tonne shrimp)     (kg) (kg/tonne shrimp) 
Total suspended solids  32,049 411.9  39,359 476.0 
BOD5 3,019 38.8  5,230 63.3 
Total nitrogen  1,076 13.8  1,315 15.9 
Total phosphorus  77.4 0.99  120.7 1.46 
Chloride 352,848 4,535  353,710 4,278 
103 
 
 
 
 
Table 3.  Concentrations of water quality variables in a creek upstream of an inland, low-
salinity shrimp farm contrasted with downstream concentrations of the variables during 
draining of ponds for harvest in 2008. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Variable 
Upstream  Downstream 
18 Sep  18 Sep             7 Oct 
pH 7.16  7.18 7.18 
Total suspended solids (mg/L) 50.00  55.00 70.00 
Turbidity (NTU) 20.60  34.90 66.20 
BOD5 (mg/L) 6.09  10.12 21.04 
Total nitrogen (mg/L) 1.29  3.97 5.90 
Total phosphorus (mg/L) 0.12  0.24 0.30 
Chloride (mg/L) 150  2,124 1,672 
104 
 
 
 
 
 
 
 
Fig. 1.  Map of the inland, low-salinity shrimp farm in Alabama where the study was 
conducted. 
 
 
 
 
 
 
 
 
 
N 
105 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Fig. 2.  Mean concentrations and standard deviations for water quality variables measured 
at different stages of pond water level drawdown for harvest at an inland, low-salinity 
shrimp farm in Alabama. 
Total suspended solids (mg/L)
0 250 500 750
W
ate
r r
em
ain
ing
 (%
)
0
25
50
75
100
Suspended solids (ml/L)
0 5 10 15
0
25
50
75
100
Turbidity (NTU)
0 200 400 600
0
25
50
75
100
Total phosphorus (mg/L)
0.0 0.5 1.0 1.5
W
ate
r r
em
ain
ing
 (%
)
0
25
50
75
100
Total nitrogen (mg/L)
0 5 10 15
0
25
50
75
100
Chloride (mg/L)
0 2000 2200 2400 2600
W
ate
r r
em
ain
ing
 (%
)
0
25
50
75
100
Total dissolved solids (mg/L)
0 2500 3000 3500 4000
0
25
50
75
100
pH
0 7 8 9
0
25
50
75
100
Biochemical oxygen demand (mg/L)
0 20 40 60
0
25
50
75
100