SALINITY VARIATION IN DUMP LAKE, RUM CAY, BAHAMAS OVER THE LAST MILLENNIUM

Past salinity of lakes on Rum Cay, Bahamas is determined by the frequency of hurricanes- times of low frequency of hurricanes corresponds to elevated salinity, while periods characterized by high frequency of hurricanes corresponds to lowered salinity. We created a transfer function to convert preserved ostracode assemblages from a sediment core from Dump Lake on Rum Cay, Bahamas to past salinity to determine how past tropical storm activity affected lakes on Rum Cay.

We analyzed thirty-two sediment modern assemblages from lakes on Rum Cay for ostraocode species abundances as well as six environmental factors: conductivity (salinity), dissolved oxygen, alkalinity, water temperature, pH, oxidation-reduction potential. We found that ostracode assemblages changed uniquely and independently with variation in conductivity. Therefore, we created a transfer function to express preserved ostracode assemblages in terms of past conductivity, with an r² of 48.8% when predicting the conductivity of other sites using a leave-one-out method.

We then applied this transfer function to sedimentary archives from the last ~1,000 years from Dump Lake on Rum Cay. With preliminary radiocarbon dating of leaves and other allochtonous material in the sediments preserved from Ru Cay, we find that times of strong El Niños correspond to elevated salinity in Dump Lake. This is caused by a reduction in hurricanes and tropical storms hitting Rum Cay, and thus delivering fresh water to lower the salinity of Dump Lake, during times of strong El Niños. Strong El Niños case high upper altitude wind shear, inhibiting the formation of tropical storms that would deliver fresh water to Dump Lake.