CHARACTERIZING THE VARIABILITY OF NON-MARINE OSTRACODE FAUNAS ON SAN SALVADOR ISLAND, BAHAMAS

Ostracode faunas from lakes on San Salvador Island, Bahamas show a remarkable correlation to environmental conditions. We examined the variability of these faunas, documenting their chemical affinities as well as species distributions. San Salvador Island represents a unique ‘natural laboratory’ in which to examine these questions because it has multiple inland lakes that have a wide range of water chemistries. Multiple replicated transects were made at each site along with corresponding water samples and baseline water chemistry measurements. Of the 60 ostracode species present in the lakes on San Salvador, only one species is present in all 14 lakes while 33 species are found in one lake only. Since the lakes are so close in proximity to one another and some are connected via conduits to the ocean, the uniqueness of each lake’s fauna is noteworthy. In addition, there is a positive correlation between lake surface area and species richness, with the largest lake having a surface area of 4.4 km2 and 44 species, 19 of which are unique to that lake. Salinity also appears to be correlated to species richness. As average salinity increases, species richness decreases. Most hypersaline lakes have fewer species unique to those lakes and tend to have species that are more cosmopolitan, with wider environmental tolerances. Water chemistry analyses indicate that the sampled lakes have varying salinities, most within the saline to hypersaline range. Chloride concentrations in the ponds vary from 381 to 1963 mM with major cations being dominated by Na (1270-9870 mM), Mg (68-308 mM), Ca (8-62 mM) and K (1-20 mM). Thus, the ostracode faunas found in lakes on San Salvador Island appear to be correlated with lake area, overall salinity and salinity range. These differences could account for the high number of uniques in each lake, even though the lakes themselves are in close physical proximity to one another on the island.