Dissertation Research:Shifting Baselines? The ecological implications of simultaneous eutrophications and overfishing

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Shifting Baselines? The ecological implications of simultaneous eutrophication and overfishingOverfishing and human-derived nutrient pollution are among the most pressing issues facing coastal environments globally. Both these stressors affect the supply of growth-limiting nutrients (nitrogen (N) and phosphorus (P)) for algae and seagrasses, the base of most marine ecosystems. Human inputs increase the supply of nutrients, which are largely sewage-derived, while overfishing has been shown to reduce nutrient supply because fish provide substantial inputs of nutrients via excretion. These contrasting inputs present the paradox that human-derived nutrients may supplant fish-derived nutrients. However, human-derived nutrients are high in P relative to fish-derived nutrients, which may be altering the baseline at which nutrients are supplied and in turn changing the diversity and growth rates of algae and seagrass species. Overfishing and nutrient enrichment will be simulated independently and simultaneously on experimental patch-reef ecosystems in the Bahamas. The implications for changes in diversity, growth and nutrient limitation of algae and seagrass species will be determined . The experimental reef system will be used as a field trip site and experimental results will be used in outreach efforts to local high school students. Subtropical and tropical marine ecosystems have evolved to function under extremely low nutrient conditions, making them particularly susceptible to even minor alterations in nutrient dynamics. The enormous services provided by these ecosystems appear to critically hinge on the amount and relative supply of N and P, yet understanding of the effects of simultaneous overfishing and eutrophication for these services is lacking, particularly in the Caribbean. Increased understanding of nutrient effects is critical to the management and conservation of marine ecosystems globally.