Fundulus grandis otolith microchemistry as a metric of estuarine discrimination and environmental conditions in the northern Gulf of Mexico

Abstract

The Gulf Killifish Fundulus grandis is an important component of saltmarsh ecosystems and is an ideal choice as an indicator species for environmental changes, given that it remains near the same marsh throughout its life. Also, their otoliths may provide a record of environmental conditions experienced by a given fish, because they are metabolically inert, grow continuously with fish growth, and incorporate trace elements from the environment. In this study, I used laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) to asses whether the otoliths of F. grandis along the N. Gulf of Mexico coast that were exposed to oil as a result of the 2010 Deepwater Horizon oil spill and as a result of being in close proximity to an oil refinery, contained trace elemental markers that could be attributed to oil exposure. Paired oiled and non-oiled sites did not differ in trace metals shown to be associated with oil. However, concentrations of Mn55, Sr86, Sr88, and Ba137 varied among sites and allowed for discrimination of estuaries in Louisiana and the west side of Mobile Bay Alabama from other regions when sites were combined. Sites in Mississippi, Florida, and the east side of Alabama were unable to be separated from one another, given that concentrations of these three elements and two Sr isotopes were similar among these regions. Mn55 was indicative of Alabama sites on the west side of Mobile Bay, especially the Fowl River site, and Ba137 was shown to be an effective marker for F. grandis collected from Louisiana. Salinity and temperature also had significant effects on Sr and Ba incorporation into otoliths.