Hard Clam (Mercenaria mercenaria L.) Response to a Warming Environment: A Mesocosm Experiment

Abstract

The Northern quahog (Mercenaria mercenaria), known also as the hard clam, is a cultural, economic, and ecologically important species endemic to the east coast of North America. Numerous studies have indicated that water temperature and food supply are the primary factors contributing to the success of the species. The response of the hard clam to warming trends in Narragansett Bay has yet to be fully investigated due to the challenge of isolating the impact of temperature alone on local populations. In this study, mesoscale physical models of Narragansett Bay were used to replicate conditions within the Providence River Estuary that could affect hard clams. The response of clams to nutrient-stimulated phytoplankton blooms, historically polluted sediment (Legacy pollution), and three different temperature treatments: ambient, warm (3°C above ambient), and cold (3°C below ambient) were assessed using measurement of the condition, growth, and reproductive response of the hard clam. Using an ordinal logistic regression, warm treatments were found to have poorer condition and were less likely to be reproductive when compared to cold and ambient treatments. Legacy pollution did not have a significant effect on the response of the hard clam. With Narragansett Bay temperatures projected to increase 1– 6°C by the turn of the century, the results of this analysis indicate that the current hard clam fishery may struggle with future warming of the Bay.