Stable isotope analysis of Gorgonia ventalina: Spatial variability and trophic status as indicated by nitrogen-15

First documented in 1996, a fungal disease has been affecting sea fan corals throughout the Caribbean. We examined the delta15N content of (Gorgonia spp.) sampled from various sites in the Florida Keys (USA), San Salvador (Bahamas), and Puerto Rico to test the hypothesis that delta15N of Keys samples would yield a more enriched signature due to differences in human impacts and if enrichment correlates with disease dynamics. Overall, tissue delta15N values ranged from 1.2 to 4.3‰ with significantly higher values in Keys sea fans (mean +/- SE, Keys 3.7 +/- 0.4‰ vs. San Sal 2.1 +/- 0.8‰) supporting our hypothesis of greater anthropogenic input of N in the Florida Keys. Compared to delta15N of various reef species, Gorgonia spp. are trophically similar to other primary producers. We suggest that isotope analysis of corals or other long-lived species may be useful for providing a temporally integrated measure of local water quality.