Abstract

BackgroundOysters play important roles in estuarine ecosystems but have suffered recently due to overfishing, pollution, and habitat loss. A tradeoff between growth rate and disease prevalence as a function of salinity makes the estuarine salinity transition of special concern for oyster survival and restoration. Estuarine salinity varies with discharge, so increases or decreases in precipitation with climate change may shift regions of low salinity and disease refuge away from optimal oyster bottom habitat, negatively impacting reproduction and survival. Temperature is an additional factor for oyster survival, and recent temperature increases have increased vulnerability to disease in higher salinity regions.Methodology/Principal FindingsWe examined growth, reproduction, and survival of oysters in the New York Harbor-Hudson River region, focusing on a low-salinity refuge in the estuary. Observations were during two years when rainfall was above average and comparable to projected future increases in precipitation in the region and a past period of about 15 years with high precipitation. We found a clear tradeoff between oyster growth and vulnerability to disease. Oysters survived well when exposed to intermediate salinities during two summers (2008, 2010) with moderate discharge conditions. However, increased precipitation and discharge in 2009 reduced salinities in the region with suitable benthic habitat, greatly increasing oyster mortality. To evaluate the estuarine conditions over longer periods, we applied a numerical model of the Hudson to simulate salinities over the past century. Model results suggest that much of the region with suitable benthic habitat that historically had been a low salinity refuge region may be vulnerable to higher mortality under projected increases in precipitation and discharge.Conclusions/SignificancePredicted increases in precipitation in the northeastern United States due to climate change may lower salinities past important thresholds for oyster survival in estuarine regions with appropriate substrate, potentially disrupting metapopulation dynamics and impeding oyster restoration efforts, especially in the Hudson estuary where a large basin constitutes an excellent refuge from disease.

Highlights

  • Estuaries are biologically productive, supporting rich fisheries and diverse habitats, including oyster reefs, sea grass meadows, and vast expanses of fringing marshes

  • The model calculates the vertical salinity structure as well as the along-estuary distribution, and here we focus on salinities in the relatively shallow regions on the east side of Tappan Zee-Haverstraw Bay (TZ-HB) where leases for oyster culture were maintained in the 1950s and where restoration is most likely [40]

  • Our modeling results suggest that discharges consistent with precipitation in future climate scenarios could decrease salinities in the region to levels below the threshold for oyster survival

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Summary

Introduction

Estuaries are biologically productive, supporting rich fisheries and diverse habitats, including oyster reefs, sea grass meadows, and vast expanses of fringing marshes. Their very richness coincides with human habitation, which has resulted in damage from pollution, overfishing and habitat destruction. Oysters play important roles in estuarine ecosystems but have suffered recently due to overfishing, pollution, and habitat loss. Estuarine salinity varies with discharge, so increases or decreases in precipitation with climate change may shift regions of low salinity and disease refuge away from optimal oyster bottom habitat, negatively impacting reproduction and survival. Temperature is an additional factor for oyster survival, and recent temperature increases have increased vulnerability to disease in higher salinity regions

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