Long Island Sound molluscan data: live-dead fidelity, N and C stable isotopes, and predation traces

Benthic communities in Long Island Sound have experienced over 150 years of eutrophication and commercial shellfishing. We established an ecological baseline using a combination of live, dead, archaeological, and fossil mollusk material to investigate the impacts of these stressors on the molluscan community. We expected ecological change would increase with nutrient loading and eutrophication-induced hypoxia west towards New York City. Instead, crushing predation on bivalves has been suppressed below pre-anthropogenic baseline levels throughout the Sound, even in the well oxygenated east. Taxonomic similarity, rank order abundance, and drilling frequency are more strongly controlled by commercial fishing pressure than by declines in water quality. The absence of a clear relationship between eutrophication-hypoxia and ecological change questions the effectiveness of nitrogen reduction alone as a restoration strategy. Long Island Sound fossils revealed a relatively ancient loss of mollusks associated with seagrass and oyster habitats that predates death assemblage deposition and underscores the need for older material to reveal the shifting baseline. The interactive nature of multiple stressors means that overfishing may have dampened the response of communities in the Sound to eutrophication or inhibited their ability to recover. The unexpected role of hypoxic areas protected from commercial fishing as refuges highlights the utility of no-take marine preserves in eutrophied estuaries worldwide.