RESILIENCE AGAINST PERTURBATION: RESPONSE OF MOLLUSCAN COMMUNITIES TO SEA LEVEL RISE IN AN INLAND BLUE HOLE, ELEUTHERA, BAHAMAS

Sea level change presents a serious threat to the stability of coastal marine ecosystems. Inland blue holes, which are karst lakes that form in response to sea-level fluctuations, offer a means by which to examine biological response to sea level changes. They often contain small, isolated populations of gastropods and bivalves and are connected to the marine realm through a subterranean conduit system that allows lake salinity and water level to vary through time with variation in sea level. We used molluscan communities found in a blue hole on Eleuthera, Bahamas, to determine how sea level changes in the past have impacted these communities. Shells from which data were derived were collected from lake sediment cores spanning the past 6,500 years. Mollusk shells were used because they preserve well and are found in abundance throughout the cores. Mg:Ca ratios in ostracod tests from the same cores were used as a proxy to establish the changing salinity through time. Preliminary results show that the mollusk community in Duck Pond Blue Hole shifts drastically from bivalve dominance to grazing gastropods at approximately 2000 ybp. Bivalves in the cores appear to be more abundant at times of higher salinities, and drill hole frequency also changes in correspondence with changes in community structure and salinity. Response of these communities will give insight as to possible community changes due to future sea level rise and demonstrates the relative resilience of gastropods and bivalves to salinity changes due to sea level rise.