INTRALAKE VARIABILITY IN OSTRACODE ASSEMBLAGES FOR USE IN PALEOENVIRONMENTAL RECONSTRUCTION: A CASE STUDY FROM SAN SALVADOR ISLAND, BAHAMAS

Quantitative paleoenvironmental models are based on the collection of both modern assemblages at various sites and measurement of environmental variables that drive the distribution of those assemblages. The resulting data set is used to infer past environments by transforming percent abundances of fossil species into the environmental variable controlling their modern distribution. Many quantitative paleoenvironmental models rely on a few samples of fossil assemblages per site, normally lakes. This method assumes that a few samples can capture an entire lake's community. This assumption could be violated if one lake is made up of many habitats or if taphonomic processes obscure modern environmental gradients. This study tests this assumption using Ostracoda (Phylum: Arthropoda) in lakes on San Salvador Island, Bahamas by quantifying multiple living and dead assemblages per lake. In March 2009, 16 living and dead ostracode assemblages were quantified in 7 lakes along an interlake salinity gradient to test for intralake and interlake community variation. Living and dead assemblages were highly and significantly rank-correlated in most lakes. Within most individual lakes, assemblages quantified at specific locations were highly and significantly rank-correlated to assemblages quantified at other locations, indicating little intralake variability in ostracode communities. Finally, non-metric multidimensional scaling on the Bray-Curtis dissimilarity matrix with analysis of similarity indicated significant differences in community structure between and not within most lakes. The only exceptions to these results occurred in deep, tidally influenced blue holes with seasonal subaerial exposure, where living and dead assemblages were less correlated and intralake variability was more pronounced. The correlation between living and dead communities and the lack of intralake variability make ostracode communities on San Salvador Island, Bahamas a good system to use for paleoenvironmental reconstruction. This study will be used in interpreting paleoclimate records from cores on the island.