Interactive effects of ocean acidification, elevated temperature, and reduced salinity on early-life stages of the Pacific oyster

Ocean acidification (OA) effects on larvae are partially attributed for the rapidly declining oyster production in the Pacific Northwest region of the United States. This OA effect is a serious concern in SE Asia, which produces >80% of the world's oysters. Because climate-related stressors rarely act alone, we need to consider OA effects on oysters in combination with warming and reduced salinity. Here, the interactive effects of these three climate-related stressors on the larval growth of the Pacific oyster, Crassostrea gigas, were examined. Larvae were cultured in combinations of temperature (24 and 30 °C), pH (8.1 and 7.4), and salinity (15 psu and 25 psu) for 58 days to the early juvenile stage. Decreased pH (pH 7.4), elevated temperature (30 °C), and reduced salinity (15 psu) significantly delayed pre- and post-settlement growth. Elevated temperature lowered the larval lipid index, a proxy for physiological quality, and negated the negative effects of decreased pH on attachment and metamorphosis only in a salinity of 25 psu. The negative effects of multiple stressors on larval metamorphosis were not due to reduced size or depleted lipid reserves at the time of metamorphosis. Our results supported the hypothesis that the C. gigas larvae are vulnerable to the interactions of OA with reduced salinity and warming in Yellow Sea coastal waters now and in the future.

海洋酸化（OA）对幼虫的影响被部分归因于美国太平洋西北地区牡蛎产量的快速下降。这种OA效应在东南亚地区引起了严重关注，该地区的牡蛎产量占全球的80%以上。由于气候相关压力因子很少单独作用，我们需要结合变暖与盐度降低来考虑OA对牡蛎的影响。本研究考察了这三种气候相关压力因子对太平洋牡蛎（Crassostrea gigas）幼虫生长的交互效应。幼虫在温度（24℃和30℃）、pH值（8.1和7.4）及盐度（15 psu和25 psu）的不同组合条件下培养58天，直至早期幼体阶段。降低的pH值（pH 7.4）、升高的温度（30℃）及降低的盐度（15 psu）显著延迟了附着前后的生长。升高的温度降低了幼虫的脂质指数（生理质量的一个指标），且仅在25 psu盐度下抵消了降低的pH值对附着与变态的负面影响。多重压力因子对幼虫变态的负面影响并非由于变态时体型减小或脂质储备耗尽所致。我们的结果支持如下假设：当前及未来，黄海沿岸水域中太平洋牡蛎（C. gigas）幼虫易受OA与盐度降低及变暖的交互作用影响。