Using Otolith Microchemistry Of Gulf Killifish (Fundulus grandis) To Differentiate Estuaries and Identify Chemical Signatures Indicative Of Oil Exposure

The Gulf killifish (Fundulus grandis) is an important component of coastal marsh ecosystems.  Because individuals move little remaining close to the marsh throughout their life, they are a potential indicator species for environmental impact studies.  Additionally, fish otoliths grow continuously, providing a record of growth and incorporating microchemical markers from the surrounding environment. Here we sampled F. grandis from 10 sites across 4 states in the northern Gulf of Mexico.  Louisiana and Alabama both had paired oiled/non-oiled sites (oiled sites were exposed to Deepwater Horizon oil from the 2010 spill). Sites in Mississippi included one adjacent to an oil refinery and a control site, while our Florida site was unexposed to oil. We found distinct otolith microchemical signatures across states, but paired estuaries within states could not be distinguished, suggesting minimal effects from the 2010 spill. We also found a seasonal component, with otolith microchemical differences between states being more distinct during fall versus winter.  Given the lack of paired site differences combined with increasing oil well density from east to west, we identified differences in several elements (Mg, Al, V, Cr, Cu, Zn, Se) that may serve as otolith microchemical indicators of prolonged oil exposure in this region.