DIVERSITY, ABUNDANCE AND TAPHONOMIC PATTERNS ACROSS BIVALVE DEAD ASSEMBLAGES ASSOCIATED WITH SEA GRASS BEDS, SAN SALVADOR, THE BAHAMAS

The aim of this study is to explore variation in the taxonomic composition, diversity structure, and taphonomy of bivalve assemblages found in sea grass meadows and the surrounding sandflats on San Salvador, The Bahamas. Bivalve assemblages tipically preserve specimens averaged over time intervals much greater than the original life span of individual organisms. This “time-averaging”; therefore, makes it possible to describe the biodiversity of an area using a totally nondestructive sample for monitoring communities. Moreover, shelly assemblages that accumulate after mollusks die allow for longer term comparisons between habitats. In this study, 24 samples representing 3 different zones (unvegetated sand flats, a transition zone, and sea grass beds) were collected perpendicular to the shoreline by snorkeling. A total of 4,800 bivalve shells representing 19 species were recorded at 5 localities. To estimate taphonomic conditions of the dominant species, each shell was scored based on the presence-absence of cementation, bioerosion and abrasion. Detrended correspondence analysis, based on relative abundance of species, indicates that sites with no sea grass beds could be distinguished from those with sea grass. Crenella divaricata (d’Orbigny, 1842), for example, was the dominant species in all samples, but was absent in the locality with no sea grass beds. The taphonomic signature of this dominant species indicated that sea grass samples were more pristine suggesting that bivalve assemblages associated with sea grass beds are relatively less biased by taphonomic processes.