Salinity fluctuations due to urbanization of coastal environments and their potential effect on the genetic divergence of the Gulf killifish (Fundulus grandis)

Environmental conditions are one of the main factors influencing the distribution of species across ecosystems. As humans modify both abiotic and biotic parameters across different ecosystems, it is essential to understand how anthropogenic activities can affect the distribution of species and/or populations. Changes to coastal ecosystems via urbanization can lead to rapid fluctuations in salinity of coastal areas due to the increased runoff of freshwater during storms. These fluctuations in salinity are known to promote shifts in the community structure and abundance of coastal fishes, yet questions remain on their role in shaping the genetic divergence of persistent populations. In this study, salinity of coastal watersheds was monitored in four different sites of the Pensacola Bay and Wolf-Perdido Bay drainage. Salinity records showed increasing salinity variability between sites with low, intermediate, and high urbanization. On each of these sites, differences in the mitochondrial markers cytochrome oxidase 1 (CO1) and control region (CR) were evaluated for the Gulf killifish, Fundulus grandis. The genetic results indicate the largest genetic differences were found among individuals at sites with intermediate and high urbanization, and among individuals at distant sites with intermediate and low urbanization, for CR. These results suggest that both geographic distance and differences in salinity regimes have the potential to promote genetic structure among killifish populations. Overall, the results from this study indicate that urbanization can have significant effects on the salinity regimes of the northern Gulf of Mexico, while highlighting the potential effects urbanization and geographic distance can have on genetic composition of coastal fishes.

Automated summary

Environmental conditions play a crucial role in species distribution across ecosystems. This study explored the impact of urbanization on salinity regimes and genetic composition of coastal fishes. The results indicate that urbanization increases salinity variability and promotes genetic structure among killifish populations in the Gulf of Mexico. These findings highlight the significance of understanding the effects of anthropogenic activities on coastal ecosystems.