Physiological and ecological variables measured at the high and low pCO2 reef sections@en

Experiments have shown that ocean acidification due to rising atmospheric carbon dioxide concentrations has deleterious effects on the performance of many marine organisms. However, few empirical or modelling studies have addressed the long-term consequences of ocean acidification for marine ecosystems. Here we show that as pH declines from 8.1 to 7.8 (the change expected if atmospheric carbon dioxide concentrations increase from 390 to 750 ppm, consistent with some scenarios for the end of this century) some organisms benefit, but many more lose out. We investigated coral reefs, seagrasses and sediments that are acclimatized to low pH at three cool and shallow volcanic carbon dioxide seeps in Papua New Guinea. At reduced pH, we observed reductions in coral diversity, recruitment and abundances of structurally complex framework builders, and shifts in competitive interactions between taxa. However, coral cover remained constant between pH 8.1 and ~7.8, because massive Porites corals established dominance over structural corals, despite low rates of calcification. Reef development ceased below pH 7.7. Our empirical data from this unique field setting confirm model predictions that ocean acidification, together with temperature stress, will probably lead to severely reduced diversity, structural complexity and resilience of Indo-Pacific coral reefs within this century.实验结果表明，大气二氧化碳浓度升高引发的海洋酸化，对多种海洋生物的生存表现具有有害影响。然而，针对海洋酸化对海洋生态系统造成的长期后果，现有实证与模型研究仍较为匮乏。本研究针对pH值从8.1降至7.8的场景（该变化对应大气二氧化碳浓度从390ppm升至750ppm，与本世纪末部分预测情景相符），发现部分海洋生物将从中获益，但更多类群将受到不利影响。我们对巴布亚新几内亚三处凉爽浅海的火山二氧化碳喷口区的珊瑚礁、海草床与沉积物开展了调查，这些生境中的生物已适应低pH环境。在pH值降低的区域，我们观测到珊瑚多样性、补充量以及结构复杂造礁生物的丰度均出现下降，同时类群间的竞争互作关系发生改变。不过，尽管块状滨珊瑚（Porites）的钙化速率较低，但其相较于结构型珊瑚占据了优势地位，因此珊瑚覆盖率在pH 8.1至约7.8的区间内仍保持稳定。当pH值低于7.7时，珊瑚礁的发育完全停止。本研究在这一独特野外生境中获取的实证数据，验证了模型预测结果：海洋酸化与温度胁迫共同作用，或将在本世纪内大幅降低印太珊瑚礁的多样性、结构复杂度与恢复力。