Hawksbill turtle (Eretmochelys imbricata) nests: Possible nutrient sources and drivers of community structure in a tropical marine system
Beach environments are considered nutrient poor systems that support limited abundances of life due to the lack of attainable nutrients. Since the surrounding environment is nutrient limited, plants and organisms residing in sandy beach communities take advantage of available nutrients whenever possible, for example, nests laid on the beach. This study assessed whether nesting hawksbill sea turtles (Eretmochelys imbricata) are transporters of nutrients from ocean systems to nutrient-poor beaches of Bonaire, N.A. It was hypothesized that nitrogen (N) and phosphorus (P) levels would be elevated, infaunal organisms would be more abundant, and plant cover would be higher in nest plots compared to areas without nests. To determine the input of nutrients from nesting and the potential effects of nutrient enrichment on the plants and infauna, five experimental arrays, including nest, mechanically disturbed (no nutrient addition), and undisturbed treatments were sampled from September to October 2009 on Klein Bonaire. Five days following hatching events, sediment cores were taken to assess concentrations of N and P, as well as to determine the abundance of infauna. Plant percent cover was also determined for each plot. Nutrients did not differ significantly among plot type, with both N and P consistently at low concentrations. For all nest plots, 2.5 X more taxonomic groups, including known predators, were detected than in undisturbed or mechanically disturbed plots. No plants were found in any plot type for the duration of the study. This study suggests that hawksbill sea turtle nests are not strong drivers of coastal community structure in Bonaire. It is believed that the CaCO3 composition of the sand and the limestone base of the island do not allow for nutrient retention and thus excess nutrients are not available for exploitation by beach plants or infauna.