Climate Change, Precipitation and Impacts on an Estuarine Refuge from Disease

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.

Klamath River Thermal Refuge Provides Juvenile Salmon Reduced Exposure to the Parasite Ceratonova shasta

“…However, the potential for these refuges to function as disease refuges has not been examined. Disease refuges have been defined as "areas within the host range where disease is absent or sufficiently low to have little impact on the survival or reproductive success of susceptible individuals (i.e., exerts no selection pressure)" (Hofmann et al 2009;Levinton et al 2011). We demonstrated that the thermal refuge at the Beaver Creek-Klamath River confluence served as a disease refuge for juvenile salmonids to varying degrees throughout the summer by (1) providing an area of decreased C. shasta exposure and/or (2) providing relatively lower water temperatures that alleviate ceratomyxosis in juveniles infected in the Klamath River main stem.…”

Identification and characterisation of an ostreid herpesvirus-1 microvariant (OsHV-1 µ-var) in Crassostrea gigas (Pacific oysters) in Australia

“…The effect of rainfall on OsHV-1 transmission has not been investigated; however, rainwater run-off is a known stressor for oysters due to the influx of freshwater and a corresponding decrease in salinity (Levinton et al 2011). Historical records indicate that both Woolooware and Quibray Bays are high-salinity areas.…”

Proteomics of hyposaline stress in blue mussel congeners (genusMytilus): implications for biogeographic range limits in response to climate change

“…Although more extreme precipitation events due to higher atmospheric humidity levels associated with climate change have been documented (Groisman et al, 2005;Min et al, 2011), biologists are only now starting to evaluate the potential impacts of these events, e.g. greater levels of hyposaline stress, on species distribution ranges (Levinton et al, 2011). Extreme precipitation events will occur in a warmer world even if total precipitation levels do not increase (Karl and Trenberth, 2003).…”