LATE HOLOCENE CLIMATE CHANGE RECORDS FROM THREE LAKES ON SAN SALVADOR ISLAND, BAHAMAS

High resolution records of past environments are needed to understand natural ecosystem variability and how global and regional climate changes are reflected in local environments. A transfer function is a method of quantitative paleoenvironmental reconstruction whereby preserved microfossil assemblages are converted into an abiotic environmental variable of interest. This method depends on a strong correlation between modern assemblages and the abiotic environment that is then applied to preserved microfossil assemblages to produce a record of past abiotic factors. We collected modern ostracode assemblages and 19 associated environmental variables from 32 lakes on San Salvador Island, Bahamas in order to construct a transfer function to extract paleoenvironmental records from preserved lacustrine ostracode assemblages. Multivariate fuzzy set ordination revealed that faunal change in ostracode assemblages was correlated with a complex hydrological gradient consisting of conductivity, dissolved oxygen, and alkalinity. A transfer function was constructed for conductivity, as a proxy for salinity, since changing salinity of individual lakes has been linked to changes in climate and sea level. This transfer function has comparable precision to other published ostracode-based transfer functions for conductivity, including an apparent r² of .74 and a leave-one-out cross validation r² of .68.

This transfer function was then applied to ostracode assemblages from three lakes on San Salvador Island, Bahamas: Clear Pond, Salt Pond, and North Storr's Lake. Records from Clear Pond reveal moderately increasing salinity over the approximately 5200 year record recovered, but with many non-cyclical reversals. Records from Salt Pond reveal wide cyclical fluctuations in salinity with an approximately 100 year cycle, as determined by spectral analysis, over the ~2400 year record recovered. Records from North Storr's Lake include both times of stable salinity and 100 year cycles similar to those in Salt Pond over its ~6500 year record. Taken together, these records indicate asynchronous changes in salinity of individual lakes on San Salvador, but that certain lakes, like Salt Pond and perhaps North Storr's lake, may be responding to high frequency climate oscillations such as ENSO or NAO.