CONSERVATION PALEOBIOLOGY AND THE MOLLUSK COMMUNITY RESPONSE TO CLIMATE AND SEA LEVEL CHANGES IN AN INLAND BLUE HOLE--DUCK POND BLUE HOLE, ELEUTHERA, THE BAHAMAS

Duck Pond Blue Hole is a small (.001 km²) circular karst dissolution feature located on the southern portion of Eleuthera Island, Bahamas. A conduit linking it with the ocean creates a tidally influenced environment that has been responsive to sea level change through time. Mollusks of both lacustrine and marine origin were found in cores taken at three sites within the lake. Radiocarbon dating suggests a record back to 6000 years before present for the cores from our deepest-water site. While mollusks occur throughout the cores in varying abundances, they are concentrated in beds that correlate with grain size shifts. Faunal elements include three species of bivalves (Anomalocardia auberiana, Ervilia concentrica, and Polymesoda maritime) and five species of gastropods (Acteocina sp., Batillaria minima, Cerithidea costata, Cerithium lutosum, and Heleobops sp.). There is a faunal shift from a bivalve dominated community to a gastropod dominated community at approximately 2000 cal yBP with less than 1% of the gastropods occurring before that time. Within the bivalve community, the most common species is Anomalocardia auberiana which accounts for greater than 57% of the overall mollusk community through time. In general there is a positive correlation between the presence of A. auberiana and other bivalve species. Gastropods dominate the fauna from 2000 cal yBP to present with the Cerithidea costata being the most abundant species at 6.6% of the fauna. Predaceous drill holes are found on both bivalves and gastropods but are predominantly found on the three bivalve species. Drilling frequency is highest between 5000 and 2500 cal yBP, even though gastropods were rare during this interval of time. In addition, plotting the depth of the shell beds versus calibrated age shows a distinct sea level curve for the past 6000 years with a rapid rise and subsequent fall at approximately 2500 cal yBP. This also corresponds with the largest amount of mollusks present and the highest drilling frequency. This record is similar to other mollusk assemblages found in two blue holes on San Salvador Island and demonstrates a biotic response to climate and sea level change as well as the effect of human occupation after the arrival of the Lucayan people at 800 CE and the onset of the Loyalist period in the late 1700’s CE.