Data from: Coralline algae in a naturally acidified ecosystem persist by maintaining control of skeletal mineralogy and size

To understand the effects of ocean acidification (OA) on marine calcifiers, the trade-offs among different sublethal responses within individual species and the emergent effects of these trade-offs must be determined in an ecosystem setting. Crustose coralline algae (CCA) provide a model to test the ecological consequences of such sublethal effects as they are important in ecosystem functioning, service provision, carbon cycling and use dissolved inorganic carbon to calcify and photosynthesize. Settlement tiles were placed in ambient pH, low pH and extremely low pH conditions for 14 months at a natural CO2 vent. The size, magnesium (Mg) content and molecular-scale skeletal disorder of CCA patches were assessed at 3.5, 6.5 and 14 months from tile deployment. Despite reductions in their abundance in low pH, the largest CCA from ambient and low pH zones were of similar sizes and had similar Mg content and skeletal disorder. This suggests that the most resilient CCA in low pH did not trade-off skeletal structure to maintain growth. CCA that settled in the extremely low pH, however, were significantly smaller and exhibited altered skeletal mineralogy (high Mg calcite to gypsum (hydrated calcium sulfate)), although at present it is unclear if these mineralogical changes offered any fitness benefits in extreme low pH. This field assessment of biological effects of OA provides endpoint information needed to generate an ecosystem relevant understanding of calcifying system persistence.

为明确海洋酸化（OA）对海洋钙化生物的影响，需在生态系统背景下解析单个物种内不同亚致死响应间的权衡效应，以及此类权衡所催生的涌现效应。壳状珊瑚藻（CCA）可作为测试这类亚致死效应生态后果的模式生物，因其在生态系统功能维持、生态服务供给、碳循环过程中发挥关键作用，且依赖溶解无机碳完成钙化与光合作用。研究人员将定植板部署于天然CO2喷口区域的环境pH、低pH及极低pH三种条件中，开展为期14个月的原位实验。分别在定植板投放后的3.5、6.5及14个月时，对CCA斑块的尺寸、镁（Mg）含量及分子尺度骨骼无序度进行检测评估。尽管低pH环境下CCA的种群丰度有所下降，但来自环境pH与低pH区域的最大CCA个体尺寸相近，镁含量及骨骼无序度也无显著差异。这提示，在低pH环境中适应性最优的CCA并未通过牺牲骨骼结构来维持生长。然而，定植于极低pH环境的CCA个体尺寸显著更小，且骨骼矿物学特征发生改变（由高镁方解石转变为石膏（水合硫酸钙）），但目前尚不明确这类矿物学变化是否能为极端低pH环境下的CCA带来适合度收益。本项针对海洋酸化生物效应的野外评估，可为构建贴合生态系统实际的钙化系统存续认知提供所需的核心终点指标信息。