Octocorals as indicators of anthropogenic nutrients

Coastal ecosystems are influenced by anthropogenic nutrients. Increased nutrient loading has not been directly linked to the source of the nutrients because of the inadequacies of current nutrient sampling methods. I propose to use N stable isotope analysis of octocorals as proxies of environmental N availability. Gorgonia ventalina collected on reefs surrounding San Salvador, Bahamas have significantly different delta15N consistent with human impacts. Octocoral within the family Gorgoniidae have similar delta15N within sites; thus species within a family may be used interchangeably. Depth has a significant influence on delta 15N. Pseudopterogorgia americana collected over a 9 m range varied by ∼1.25‰ (r2 = 0.5453). This study has shown that octocorals provide reef-to-reef variation in delta 15N consistent with human impact at these reefs, thus they are a good proxy for anthropogenic nutrients.