Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York, United States of America.
PLoS One. 2011 Apr 28;6(4):e18849. doi: 10.1371/journal.pone.0018849.
Oysters 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 FINDINGS: We 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/SIGNIFICANCE: Predicted 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.
牡蛎在河口生态系统中发挥着重要作用，但由于过度捕捞、污染和生境丧失，它们的数量近年来有所减少。由于盐度的变化会影响生长速度和疾病流行率，因此河口盐度的变化特别值得关注，因为它会影响牡蛎的生存和恢复。河口盐度随流量而变化，因此气候变化导致的降水增加或减少可能会使低盐水域和疾病避难所远离最佳牡蛎底栖生境，从而对繁殖和生存产生负面影响。温度是牡蛎生存的另一个因素，最近温度的升高增加了高盐度地区对疾病的易感性。
方法/主要发现：我们研究了纽约港-哈德逊河地区牡蛎的生长、繁殖和生存情况，重点关注河口的一个低盐度避难所。观测期为两年，这两年的降雨量高于平均值，与该地区未来降雨量的增加相当，而过去大约 15 年的降雨量较高。我们发现牡蛎的生长和对疾病的易感性之间存在明显的权衡。当牡蛎在两个夏季（2008 年和 2010 年）暴露在中等盐度下，且流量条件适中时，它们的生存状况良好。然而，2009 年降水和流量的增加降低了该地区具有适宜底栖生境的盐度，大大增加了牡蛎的死亡率。为了评估更长时期的河口条件，我们应用了哈德逊河的数值模型来模拟过去一个世纪的盐度。模型结果表明，历史上作为低盐度避难所的区域中，有很大一部分区域可能会因降水和流量的增加而面临更高的死亡率，而这些区域原本具有适宜的底栖生境。
结论/意义：由于气候变化，美国东北部地区的降水预计会增加，这可能会使河口地区的盐度低于对牡蛎生存至关重要的阈值，特别是在哈德逊河口，那里广阔的流域构成了一个极好的疾病避难所，这可能会破坏牡蛎的局域种群动态，阻碍牡蛎的恢复工作。
