The salinas of Bonaire: how does bird activity impact epi- and infaunal communities?
Predators can play an important role in shaping prey community structure and function through direct and indirect top-down effects. Bird predators in particular can decrease lower trophic level populations in a variety of habitats from terrestrial soils to coastal sediments. In the unique, high salinity salina habitats of Bonaire, NA top-down effects may be present as a result of the migratory bird community consuming epi- and infaunal organisms. In this study, I assessed the make-up of the bird community feeding in three salinas (Marina, Sorobon, City Shop) through morning and evening observations as well as the epi- and infaunal organisms of salina sediments through coring. The birds found to utilize the sediments of the salinas for feeding included flamingos, reddish egrets, great egrets, snowy egrets, great blue herons, plovers, and willets; different species richness per site. The coastal succulent, Sesuvium portulacastrum, and seagrass occupy the salinas from approximately 1%-8%. Snails were found in the sediments of all 3 locations (Sorobon 24.9 ± 7.6 m-2 , Marina & City shop 0.3 ± 0.58 m-2 ) and fiddler crabs (8.93 ± 4.05 m-2 ) were found only at the Marina site. In addition, I attempted to understand how the birds may structure infaunal communities through their feeding habits by using field-based feeding preference choice assays. Five plots, separated into four squares containing crabs, snails, plants, and a control (one per square), were placed at each of the three previously chosen monitoring locations. The plants and snails were not consumed in the experimental food assays, but approximately 90% of the crabs were consumed. The crab densities and percent plant coverage in the control plots remained constant to the original data collected, suggesting the feeding assay plots didn’t have an affect on the predators feeding. The presence of crabs at Marina and snails at Sorobon may be supported by the differences in sediment composition. Sediments at Marina were found to be composed of more coarser-grained particles versus the sediments at Sorobon which are more fine-grained particles. This may suggest that bottom-up effects may impact, shape the epi- and infaunal communities where potential predators are present.
This student research was retrieved from Physis: Journal of Marine Science V (Spring 2009)19: 14-19 from CIEE Bonaire.