Juvenile pen shells (Pinna nobilis) tolerate acidification but are vulnerable to warming

In the course of this century, rising anthropogenic CO2 emissions will likely cause a decrease in ocean pH, know as ocean acidification, together with an increase of water temperature. Only in the last years, studies have focused on synergetic effects of both stressors on marine invertebrates, particularly on early life stages considered more vulnerable. Disparate responses of their singular and combined effects were reported, highlighting the importance of extending the studies to different species and populations of marine invertebrates. Here, we observed the response of important parameters such as growth, mortality and oxygen consumption of juvenile pen shell Pinna nobilis at supplied pCO2 gas levels of 400 ppm (ambient) and 1000 ppm and at three temperatures (20, 23 and 26 °C) during 36 days. To our knowledge, this is the first study on ocean acidification and temperature effects on juveniles of this species. We show that the two stressors play roles at distinct levels, with pCO2 influencing growth and partially mortality, and temperature increasing mortality rates and oxygen consumption strongly. Therefore, juveniles of P. nobilis are more likely affected by increasing temperature than the pCO2 levels expected by the end of the twenty-first century.本世纪内，不断增加的人为二氧化碳（anthropogenic CO2）排放将可能导致海水pH值下降，即海洋酸化（ocean acidification），同时伴随海水温度升高。直至近年，相关研究才开始聚焦这两类胁迫因子对海洋无脊椎动物的协同效应，尤其关注被认为更易受影响的早期生命阶段。已有研究报道了单一与复合胁迫因子作用下的迥异生物响应，这凸显了将研究拓展至更多海洋无脊椎动物物种及种群的必要性。本研究设置了400 ppm（环境背景水平）与1000 ppm的二氧化碳分压（pCO2）梯度，以及20、23、26 ℃三个温度梯度，在为期36天的实验中监测了幼体笔蛤（Pinna nobilis）的生长、死亡率与耗氧率等关键生理参数的响应特征。据我们所知，本研究是首个针对该物种幼体开展的海洋酸化与温度胁迫效应相关研究。研究结果表明，两类胁迫因子的作用层级存在差异：二氧化碳分压会影响幼体生长并部分影响死亡率，而温度则会显著提升死亡率与耗氧率。因此，相较于本世纪末预期的二氧化碳分压水平，笔蛤（P. nobilis）幼体受升温的影响更为显著。