Investigating correlations between eutrophication and estuarine fish communities in the Northern Gulf of Mexico estuaries

Eutrophication and associated coastal hypoxia are significant issues that have had profound effects on estuarine environments, particularly in the Gulf of Mexico. Besides changing the physical characteristics of an ecosystem, eutrophication can significantly impact estuarine fish communities. We studied eutrophication rates in the estuaries of the Gulf of Mexico and how certain water quality parameters may be associated with abundances of commercially and ecologically important fish species. We analyzed nitrogen, phosphorus, chlorophyll a, and dissolved oxygen concentrations in three National Estuarine Research Reserve (NERR) estuaries to understand eutrophication rates of estuaries in the Gulf of Mexico. We then compared these variables with catch per unit effort (CPUE) of 7 fish species to determine potential correlations. Water quality data were collected by the NERR program and fish CPUE data were collected by state agencies utilizing fisheries independent methodologies. We found relatively few changes in eutrophication rates at these NERR sites. While nutrient and dissolved oxygen concentrations did not change significantly, there was some evidence of increasing chlorophyll a levels. Linear regression analysis of fish CPUE revealed a significant positive relationship between dissolved oxygen and CPUE of menhaden (Brevoortia patronus), a negative relationship between temperature and CPUE of striped mullet (Mugil cephalus), and a positive relationship between spotted seatrout CPUE (Cynoscion nebulosus) and temperature. Also, a significant increase in species richness of animal species was experienced in Apalachicola Bay. The increase in species richness and relatively stable water quality parameters may be a result of coastal marsh habitat of these conserved areas buffering excess nutrient inputs and creating ideal habitat for species. Future studies should analyze changes of these water quality parameters in more and less developed areas