Table_1_Impacts of Ocean Warming on Coralline Algal Calcification: Meta-Analysis, Knowledge Gaps, and Key Recommendations for Future Research.DOCX

Coralline algae are foundation species in many hard-bottom ecosystems acting as a settlement substrate, and binding together and even creating reefs in some locations. Ocean acidification is known to be a major threat to coralline algae. However, the effects of ocean warming are less certain. Here we bring multiple lines of evidence together to discuss the potential impacts of ocean warming on these ecologically crucial taxa. We use a meta-analysis of 40 responses within 14 different studies available which assessed the effects of increasing temperature on coralline algal calcification in laboratory experiments. We find a net negative impact of increasing temperature on coralline algal calcification at 5.2°C above ambient conditions. Conversely, negative effects are observed when temperature drops below 2.0°C from ambient conditions. We propose that some coralline algae will be more capable of both acclimatizing and locally adapting to increasing ocean temperatures over the coming decades. This is because many species possess short generation times, the ability to opportunistically rapidly utilize open space, and relatively high phenotypic plasticity. However, less resistant and resilient species will be those that are long-lived, those with long generation times, or with narrow thermal tolerances (e.g., tropical taxa living close to their thermal maxima). Additionally, ocean warming will occur simultaneously with ocean acidification, a potentially greater threat to coralline algae, which could also reduce any tolerance to ocean warming for many species. To maximize the potential to accurately determine how coralline algae will respond to future ocean warming and marine heatwaves, future research should use environmentally relevant temperature treatments, use appropriate acclimation times and follow best practices in experimental design.

珊瑚藻（coralline algae）是众多硬质底栖生态系统中的关键基础物种，既可作为海洋生物的附着基质，还能胶结硬质底质，在部分区域甚至可直接参与造礁过程。海洋酸化（ocean acidification）已被证实是威胁珊瑚藻生存的主要环境压力因子，但海洋变暖对其产生的生态效应尚不明确。本研究整合多维度实证证据，探讨海洋变暖对这类生态关键类群的潜在影响。我们针对已发表的14项相关研究中的40组观测数据开展荟萃分析（meta-analysis），评估实验室控制条件下升温对珊瑚藻钙化作用的影响。研究发现，当温度较环境背景值升高5.2℃时，升温会对珊瑚藻的钙化作用产生显著的净负面效应；反之，当温度较环境背景值降低2.0℃以上时，同样可观测到负面效应。我们推测，在未来数十年间，部分珊瑚藻类群将更有能力通过生理驯化和本地适应来应对海洋变暖。究其原因，该类多数物种具备世代周期短、可快速抢占空白生境的机会主义生存策略，以及相对较高的表型可塑性（phenotypic plasticity）。但对于寿命较长、世代周期长或热耐受范围较窄的类群（例如生存于接近自身热极限的热带类群），其抗逆性与恢复力则相对较弱。此外，海洋变暖往往与海洋酸化同步发生，而后者对珊瑚藻的威胁可能更为显著，这也会降低多数物种对海洋变暖的耐受能力。为尽可能精准地明确珊瑚藻对未来海洋变暖和海洋热浪的响应模式，未来相关研究应采用贴合自然环境的温度处理方案，设置合理的驯化时长，并遵循实验设计的最佳实践规范。