CHANGES IN ROCKY INTERTIDAL MOLLUSCAN ASSEMBLAGES ALONG AN ANTHROPOGENIC GRADIENT

Mollusks are sensitive to environmental and human changes and are suitable for addressing questions concerning these topics. The rich communities of the rocky intertidal zone of San Salvador, The Bahamas, provide an opportunity for studying different levels of human impact on biodiversity. In this study, mollusk communities were examined along an anthropogenic gradient present along the western coast of San Salvador. A hierarchical sampling method was implemented to study mollusk assemblages located in the brown zone of the rocky intertidal. Nine localities, comprised of 34 sites, 102 transects, and 408 quadrats, yielded 30 different species and 49,287 individuals. Size of the intertidal black and brown zone were measured while the presence or absence of the pink zone was noted. The most impacted locality and the most pristine locality had 15 species, but differ in terms of composition. The pristine locality contained 72% rare and uncommon species, while the most impacted locality contained only 0.58%. This suggests anthropogenic impact is greatest for rare species and may be driving the large differences between these two localities. Other factors that appear to impact diversity and abundance include the presence or size of the black zone. The most impacted locality contained 5,840 individuals compared to only 220 for the most pristine, but the black zone is extensive at the impacted locality and is mostly absent at the most pristine. Further assessment and analysis of both of these contributing factors may provide a more complete picture and understanding of the interactions of humans with their environment, as well as ways in which natural buffers may assist in conservation efforts.