MULTIPLE ANTHROPOGENIC STRESSORS IN LONG ISLAND SOUND AND THEIR IMPACTS ON MOLLUSCAN PREDATION: THERE'S NO ONE-SIZE-FITS-ALL RESTORATION STRATEGY

Understanding the impact of interacting anthropogenic stressors, such as eutrophication-induced hypoxia and commercial fishing pressure, on biological interactions is crucial to our ability to predict the outcome of restoration efforts in degraded ecosystems. However, restoration efforts, like that to reduce anthropogenic N loads into Long Island Sound (LIS), frequently evaluate and treat each stressor independently. Drill-hole and repair scar analyses conducted on modern death assemblages and archaeological middens were combined with soft tissue stable isotopic analysis of trophic position along LIS’s W-E eutrophication gradient, in fished and unfished areas. Contrary to ecological predictions, the removal of drilling predators by commercial fishermen has a stronger impact on the frequency of muricid and naticid drill-holes than seemingly catastrophic declines in bottom water dissolved oxygen (DO). Archaeological shell middens revealed a modern suppression of crushing predation on bivalves well below pre-anthropogenic baseline levels, even in the normoxic east, though crushing predation on drilling gastropods remained high. Sites with high drilling frequencies contain a higher proportion of the smallest, most lucrative size class of quahogs (Mercenaria mercenaria). Increases in summer DO achieved through N reduction may result in increased crushing predation on drilling gastropods causing unanticipated negative effects on populations of economically important quahogs, by disrupting the size distribution pattern, even as it helps restore hypoxia-sensitive taxa like oysters (Crassostrea virginica) and active organisms like fish. If changes in quahog distribution are felt before the recovery of other commercially important taxa they could damage the LIS fishing industry, which has increasingly relied on quahogs in recent years. The unexpected ability of severely hypoxic areas protected from commercial fishing pressure to serve as a refuge for predator populations and predator-prey interactions highlights the strength of no-take marine preserves to aid in sound conservation. While current efforts to reduce anthropogenic nitrogen loading are laudable, they may not lead to the type of ecosystem restoration anticipated in the absence of reductions in commercial fishing pressure.