School of Life Sciences, University of Essex, Colchester, UK.
Coastal & Marine Ecosystems Group, School of Biological Sciences, University of Sydney, Sydney, NSW, Australia.
Glob Chang Biol. 2021 Jul;27(13):3166-3178. doi: 10.1111/gcb.15626. Epub 2021 May 4.
Ecological communities are increasingly exposed to multiple interacting stressors. For example, warming directly affects the physiology of organisms, eutrophication stimulates the base of the food web, and harvesting larger organisms for human consumption dampens top-down control. These stressors often combine in the natural environment with unpredictable results. Bacterial communities in coastal ecosystems underpin marine food webs and provide many important ecosystem services (e.g. nutrient cycling and carbon fixation). Yet, how microbial communities will respond to a changing climate remains uncertain. Thus, we used marine mesocosms to examine the impacts of warming, nutrient enrichment, and altered top-predator population size structure (common shore crab) on coastal microbial biofilm communities in a crossed experimental design. Warming increased bacterial α-diversity (18% increase in species richness and 67% increase in evenness), but this was countered by a decrease in α-diversity with nutrient enrichment (14% and 21% decrease for species richness and evenness, respectively). Thus, we show some effects of these stressors could cancel each other out under climate change scenarios. Warming and top-predator population size structure both affected bacterial biofilm community composition, with warming increasing the abundance of bacteria capable of increased mineralization of dissolved and particulate organic matter, such as Flavobacteriia, Sphingobacteriia, and Cytophagia. However, the community shifts observed with warming depended on top-predator population size structure, with Sphingobacteriia increasing with smaller crabs and Cytophagia increasing with larger crabs. These changes could alter the balance between mineralization and carbon sequestration in coastal ecosystems, leading to a positive feedback loop between warming and CO production. Our results highlight the potential for warming to disrupt microbial communities and biogeochemical cycling in coastal ecosystems, and the importance of studying these effects in combination with other environmental stressors.
生态群落越来越多地受到多种相互作用的压力源的影响。例如，变暖直接影响生物的生理机能，富营养化刺激食物网的基础，而捕捞更大的生物体供人类食用则减弱了自上而下的控制。这些压力源在自然环境中经常以不可预测的结果结合在一起。沿海生态系统中的细菌群落是海洋食物网的基础，并提供许多重要的生态系统服务（例如营养循环和碳固定）。然而，微生物群落将如何应对气候变化仍然不确定。因此，我们使用海洋中尺度培养箱，以交叉实验设计研究了变暖、营养富集和改变顶级捕食者种群大小结构（普通滨蟹）对沿海微生物生物膜群落的影响。变暖增加了细菌的 α 多样性（物种丰富度增加 18%，均匀度增加 67%），但这被营养富集的减少所抵消（物种丰富度和均匀度分别减少 14%和 21%）。因此，我们表明，在气候变化情景下，这些压力源的一些影响可能会相互抵消。变暖和顶级捕食者种群大小结构都影响了细菌生物膜群落的组成，变暖增加了能够增加溶解和颗粒有机物质矿化的细菌的丰度，例如黄杆菌、鞘脂杆菌和噬细胞。然而，变暖引起的群落变化取决于顶级捕食者种群大小结构，较小的螃蟹增加了鞘脂杆菌的丰度，而较大的螃蟹增加了噬细胞的丰度。这些变化可能会改变沿海生态系统中矿化和碳固存之间的平衡，导致变暖与 CO2 产生之间的正反馈循环。我们的研究结果强调了变暖可能会破坏沿海生态系统中的微生物群落和生物地球化学循环的潜力，以及研究这些影响与其他环境压力源相结合的重要性。
