Cheng Brian S, Chang Andrew L, Deck Anna, Ferner Matthew C
Bodega Marine Laboratory, University of California, Davis, Bodega Bay, CA 94923, USA
Smithsonian MarineGEO, Smithsonian Environmental Research Center, Edgewater, MD 21037, USA.
Proc Biol Sci. 2016 Dec 14;283(1844). doi: 10.1098/rspb.2016.1462.
Climate change is predicted to increase the frequency and severity of extreme events. However, the biological consequences of extremes remain poorly resolved owing to their unpredictable nature and difficulty in quantifying their mechanisms and impacts. One key feature delivering precipitation extremes is an atmospheric river (AR), a long and narrow filament of enhanced water vapour transport. Despite recent attention, the biological impacts of ARs remain undocumented. Here, we use biological data coupled with remotely sensed and in situ environmental data to describe the role of ARs in the near 100% mass mortality of wild oysters in northern San Francisco Bay. In March 2011, a series of ARs made landfall within California, contributing an estimated 69.3% of the precipitation within the watershed and driving an extreme freshwater discharge into San Francisco Bay. This discharge caused sustained low salinities (less than 6.3) that almost perfectly matched the known oyster critical salinity tolerance and was coincident with a mass mortality of one of the most abundant populations throughout this species' range. This is a concern, because wild oysters remain a fraction of their historical abundance and have yet to recover. This study highlights a novel mechanism by which precipitation extremes may affect natural systems and the persistence of sensitive species in the face of environmental change.
据预测，气候变化将增加极端事件的频率和严重程度。然而，由于极端事件的不可预测性以及难以量化其机制和影响，其生物学后果仍未得到很好的解决。造成极端降水的一个关键特征是大气河流（AR），即一条狭长的增强水汽输送带。尽管近期受到关注，但大气河流对生物的影响仍未得到记录。在这里，我们利用生物数据以及遥感和现场环境数据，来描述大气河流在旧金山湾北部野生牡蛎近乎100%大规模死亡事件中所起的作用。2011年3月，一系列大气河流在加利福尼亚登陆，贡献了流域内约69.3%的降水量，并导致大量淡水排入旧金山湾。这种排放导致盐度持续偏低（低于6.3），几乎与已知的牡蛎临界盐度耐受性完全匹配，同时也与该物种分布范围内最丰富的种群之一的大规模死亡事件同时发生。这令人担忧，因为野生牡蛎数量仍远低于历史丰度，且尚未恢复。这项研究凸显了一种新机制，即极端降水可能通过该机制影响自然系统以及敏感物种在环境变化面前的存续。
