Seawater carbonate chemistry and calcification rate of cold-water coral Lophelia pertusa during experiments, 2011

Ocean acidity has increased by 30% since preindustrial times due to the uptake of anthropogenic CO2 and is projected to rise by another 120% before 2100 if CO2 emissions continue at current rates. Ocean acidification is expected to have wide-ranging impacts on marine life, including reduced growth and net erosion of coral reefs. Our present understanding of the impacts of ocean acidification on marine life, however, relies heavily on results from short-term CO2 perturbation studies. Here we present results from the first long-term CO2 perturbation study on the dominant reef-building cold-water coral Lophelia pertusa and relate them to results from a short-term study to compare the effect of exposure time on the coral's responses. Short-term (one week) high CO2 exposure resulted in a decline of calcification by 26-29% for a pH decrease of 0.1 units and net dissolution of calcium carbonate. In contrast, L. pertusa was capable to acclimate to acidified conditions in long-term (six months) incubations, leading to even slightly enhanced rates of calcification. Net growth is sustained even in waters sub-saturated with respect to aragonite. Acclimation to seawater acidification did not cause a measurable increase in metabolic rates. This is the first evidence of successful acclimation in a coral species to ocean acidification, emphasizing the general need for long-term incubations in ocean acidification research. To conclude on the sensitivity of cold-water coral reefs to future ocean acidification further ecophysiological studies are necessary which should also encompass the role of food availability and rising temperatures.

自前工业化时代以来，由于吸收人为排放的二氧化碳（anthropogenic CO₂），海洋酸度已上升30%；若二氧化碳排放维持当前速率，预计到2100年前将再升高120%。海洋酸化（ocean acidification）预计将对海洋生物产生广泛影响，包括珊瑚礁生长减缓及净侵蚀。然而，目前我们对海洋酸化影响海洋生物的认知，在很大程度上依赖于短期二氧化碳扰动研究（short-term CO₂ perturbation studies）的结果。本文呈现针对优势造礁冷水珊瑚Lophelia pertusa开展的首次长期二氧化碳扰动研究（long-term CO₂ perturbation studies）结果，并将其与短期研究结果关联，以比较暴露时间对该珊瑚响应的影响。短期（一周）高二氧化碳暴露下，pH值降低0.1个单位会导致钙化率下降26%至29%，并出现碳酸钙净溶解现象。相比之下，L. pertusa在长期（六个月）培养中能够适应酸化环境，甚至钙化率略有提升。即使在文石（aragonite）不饱和的水体中，净生长仍得以维持。适应海水酸化并未导致代谢速率出现可测量的提升。这是首个珊瑚物种成功适应海洋酸化的证据，凸显了海洋酸化研究中开展长期培养的普遍必要性。为明确冷水珊瑚礁对未来海洋酸化的敏感性，需开展进一步的生理生态学研究（ecophysiological studies），且这些研究应涵盖食物可获得性及温度升高的作用。