|The influence of instream habitat on benthic macroinvertebrates was assessed
from multiple descriptive and experimental studies within the Fort Benning Military
Installation (FBMI), Georgia and the Tuskegee National Forest, Alabama, USA.
Instream habitat, in the form of coarse woody debris (CWD), plays an important role in
stabilizing sandy bottom streams in the Coastal Plains of the Southeastern United
Chapter 2 describes the results of an instream restoration experiment conducted
in 8 streams at FBMI to assess the influence of CWD additions on instream habitat and
benthic macroinvertebrate assemblages. Macroinvertebrates were sampled before and
after CWD additions in each stream to allow pre- and post-restoration comparisons of
assemblages. Results revealed that streams receiving CWD additions dampened the
influence of hydrologic disturbance on structural and functional measures of the
macroinvertebrate assemblages, whereas non-restored streams showed a general
decrease in those same measures.
Chapter 3 describes the results of a multi-stream survey at FBMI designed to
examined the influence of catchment disturbance on instream habitat availability and its
putative effects on freshwater crayfish populations. Results showed that catchment
disturbance was negatively correlated to instream CWD and BPOM habitat and, in turn,
that crayfish density and biomass were strongly related to CWD. These data suggested
that catchment disturbance influences crayfish by influence instream habitat availability.
Chapter 4 describes a field experiment designed to quantify the influence of
crayfish on benthic food webs in sandy coastal plains streams. The experiment was
conducted in a forested section of Choctafaula creek, Macon County, Alabama, with the
Tuskegee National Forest. The experimental was an in-situ enclosure-exclosure
complete randomized block design. Results showed that crayfish had limited influence
on leaf litter (i.e., basal resource), however, they did have a significant influence on
other benthic macroinvertebrates. It appears that this influence was due to direct
predation, as determined by stable isotope analysis, which showed a trophic position
similar to other predators from the study.
Chapter 5 of this dissertation assessed crayfish production and diet from 3 sandy
bottom streams at FBMI. The purpose was to equate differences in production and diet
to differences in CWD abundance. Results showed crayfish productivity was greatest in
the stream with the highest CWD abundance, with the lowest productivity occurring in
the stream with the lowest CWD abundance. These results suggest that habitat may
plan a substantial role on crayfish productivity, and changes to habitat abundance may
negatively impact crayfish. Additionally, results showed that crayfish diets were
significantly different among streams, with crayfish from the low CWD stream containing
a high amount of inorganic matter, suggesting diets are of poor quality compared to
crayfish from streams with intermediate to high CWD.