Seawater carbonate chemistry and growth, respiration, and survival of four North Atlantic bivalves@en

We investigated the individual and interactive effects of coastal and climate change stressors (elevated temperatures, acidification, and hypoxia) on the growth, survival, and respiration rates of 4 commercially and ecologically important North Atlantic bivalves: bay scallops Argopecten irradians, Eastern oysters Crassostrea virginica, blue mussels Mytilus edulis, and hard clams Mercenaria mercenaria. Month-long experiments were performed on multiple cohorts of post-set juveniles using conditions commonly found during summer months within eutrophied, shallow, temperate, coastal environments (24-31°C; 2-7 mg O2/l; pHT, total scale, 7.2-8.0). Elevated temperatures most consistently altered the performance of the bivalves, with both positive and negative physiological consequences. Low levels of dissolved oxygen (DO) and pH individually reduced the survival, shell growth, and/or tissue weight of each bivalve, with A. irradians being the most vulnerable species. Low DO also significantly increased respiration rates of A. irradians and M. mercenaria, evidencing a compensatory physiological response to hypoxia. M. edulis and M. mercenaria both displayed size-dependent vulnerability to acidification, with smaller individuals being more susceptible. The combination of low DO and low pH often interacted antagonistically to yield growth rates higher than would be predicted from either individual stressor, potentially suggesting that some anaerobic metabolic pathways may function optimally under hypercapnia. Elevated temperature and low pH interacted both antagonistically and synergistically, producing outcomes that could not be predicted from the responses to individual stressors. Collectively, this study revealed species- and size-specific vulnerabilities of bivalves to coastal stressors along with unpredicted interactions among those stressors.本研究探究了海岸与气候变化胁迫因子（高温、酸化与低氧）对4种兼具经济与生态价值的北大西洋双壳类（bivalves）的生长、存活与呼吸速率的单因素及交互影响效应。所涉物种包括海湾扇贝*Argopecten irradians*、美洲牡蛎*Crassostrea virginica*、紫贻贝*Mytilus edulis*以及硬壳蛤*Mercenaria mercenaria*。本研究针对多批次附着后幼体开展了为期1个月的实验，实验环境设置参考富营养化浅海温带海岸夏季的常见条件：温度24~31℃、溶解氧2~7 mg O₂/L、总尺度pH值（pHT, total scale）7.2~8.0。 高温胁迫对双壳类的生理表现影响最为稳定，且可产生正向与负向的生理效应。低溶解氧（dissolved oxygen, DO）与低pH值单因素胁迫均会降低各双壳类的存活率、壳生长速率及/或组织重量，其中海湾扇贝（*A. irradians*）为最脆弱的物种。低溶解氧胁迫还可显著提升海湾扇贝与硬壳蛤的呼吸速率，表明二者存在针对低氧的代偿性生理响应。紫贻贝与硬壳蛤均表现出对酸化胁迫的体型依赖性脆弱性，个体越小则敏感性越高。 低溶解氧与低pH值的复合胁迫通常会产生拮抗交互作用，使得双壳类的生长速率高于单一胁迫下的预测值，这或暗示部分厌氧代谢通路在高碳酸胁迫（hypercapnia）下可实现最优功能。高温与低pH值的交互作用同时存在拮抗与协同效应，其产生的结果无法通过单一胁迫的响应模式进行预测。 综上，本研究揭示了双壳类对海岸胁迫因子的物种特异性与体型特异性脆弱性，同时发现了这些胁迫因子间此前未被预见的交互效应。