Sea turtle populations around the world have seen drastic declines in recent years. As commercial and private development along the coasts increase and interactions with humans continue to rise, sea turtles face intensifying threats to their survival. The loggerhead sea turtle (Caretta caretta), native to the southeastern United States, is one such species whose decline has been correlated with anthropogenic activity. Listed as federally threatened in 1978, its populations continue to decline despite major conservation efforts centered on egg and hatchling survival. Human-related threats such as incidental bycatch and pollution are among the greatest sources of mortality in juvenile and adult loggerhead sea turtles. Hence, conservation efforts have been executed in many countries since 1992. However, recent oil disasters, such as the Deepwater Horizon oil spill, raise concerns about the impact of gas and oil-related activities. The objective of our research is to determine how the event of oil spills affects the population dynamics of loggerhead sea turtles. We conducted a thorough literature review to obtain the best basic demographic data available and developed a stage-structured population dynamics model for loggerhead sea turtles using STELLA®7.0.1. We then used the model to test the potential effects of oil spills on the population of loggerhead sea turtles. Four scenarios were modeled, including a non-oil baseline scenario and three levels of oil exposure (light, average, and heavily oiled).
Results/Conclusions
The additional mortality from the oil spill resulted in declines in all stages of the population, regardless of how heavily oiled the turtles were. The significance of the decline in all three levels of oil implies the possibility of the population’s extinction despite current conservation efforts such as TEDs and nest protection. Higher mortality in the smaller stages likely results from small juveniles spending more time at the surface than adults, especially with their use of Sargassum habitat where ocean currents converge and concentrate oil. The results of this study imply that our current conservation efforts are insufficient when combined with a large oil spill event. Recommendations include focusing more on small and large juvenile stages in the post-spill collection, cleaning, and relocation efforts to increase survival in key life stages. Long term monitoring program for the effects of oil spills on loggerhead sea turtles is urgently needed.