HURRICANE EFFECTS ON MOLLUSCAN DEATH ASSEMBLAGES AND THEIR FACIES: SAN SALVADOR, BAHAMAS

Hurricanes are major agents in sediment transport, but studies in modern coral reef environments indicate that limited out-of-habitat transport occurs among the molluscan sedimentary component following major hurricanes. Such studies were largely conducted in reef environments with partially restricted bays and lagoons where seagrass beds may limit transport. In contrast, little is known about transport of molluscan skeletal carbonate after a Category 4 hurricane in open-coastal reef environments with no sediment-trapping seagrass beds. Such reefs are common in the Caribbean region, and have numerous Pleistocene fossil analogs. Three leeward reef sites were studied in San Salvador, Bahamas four months (January 2005), and eight months (June 2005) after Hurricane Frances (Cat. 4). Samples were collected every 30-m along 300-meter transects, covering beach (high-tide water mark), subtidal sand, hardground, and patch reef habitats; the latter three habitats were patchy and discontinuous.

Of the skeletal components, gastropods comprised over 7,000 individuals representing 131 taxa. One genus (Cerithium) accounted for 40% of the total individuals; rare taxa comprised 122 species (contributing < 2% of the total individuals). Most rare taxa formed substrate-specific assemblages distinguishable within the transects indicating high spatial fidelity of gastropod death assemblages even in this frequently storm-disturbed environment. Indeed, preliminary detrended correspondence analyses (DCA) show that these distinct assemblages can be recognized both four and nine months after a Cat. 4 hurricane. These findings support the importance of extensive sampling in fossil intervals where similar patchiness may have been prevalent. Furthermore, despite frequent storm disturbance, these shallow patch reef environments may have the capacity to preserve fossil assemblages with unique environmental characteristics as in seagrass-dominated reef settings.