海洋酸化，而不是变暖或热浪，通过简化栖息地，限制了范围扩大的鱼类的浅水行为

摘要(中文译文)

社会背景是行为对气候变化的适应能力的一个关键但尚未被充分探索的决定因素。群居可以通过增强警觉性、降低捕食风险和提升觅食效率来缓冲个体面对环境压力的影响。然而，这些行为表现是否在慢性（变暖、酸化）和急性（海洋热浪）气候胁迫下持续存在仍不清楚。利用涵盖当前、海洋变暖以及变暖-酸化复合条件的天然气候类似物，我们量化了群体大小如何影响一种分布范围正在扩展的礁鱼（Pomacentrus coelestis）的行为表现。在所有气候条件下，较大群体中的鱼始终表现出更高的觅食和活动水平以及更低的避险行为，而变暖、酸化和热浪对行为的直接影响可忽略不计。相比之下，海洋酸化最可能通过简化底栖栖息地间接限制了集体行为，该处鱼类密度比变暖礁区低84%，导致群体规模比变暖礁区和对照礁区小多达79%。综合来看，我们的数据表明群体大小介导了觅食与避捕之间的行为表现，而酸化驱动的栖息地简化可通过降低鱼类密度和大群体的形成来间接改变行为表现。我们得出结论：气候变化可通过栖息地驱动的社会结构侵蚀间接改变群居鱼类的行为表现。

Abstract

Social context is a critical yet underexplored determinant of behavioural resilience to climate change. Group living can buffer individuals against environmental stress through enhanced vigilance, reduced predation risk and improved foraging efficiency. However, whether these behavioural expressions persist under chronic (warming, acidification) and acute (marine heatwaves) climate stressors remains unclear. Using natural climate analogues spanning present-day, ocean warming and combined warming-acidification reefs, we quantified how shoal size influences behavioural expression in a range-extending reef fish (Pomacentrus coelestis). Across all climate conditions, fish in larger shoals consistently exhibited higher foraging and activity levels and reduced risk-avoidance behaviours, whereas direct effects of warming, acidification and heatwaves on behaviour were negligible. In contrast, ocean acidification most likely constrained collective behaviour indirectly by simplifying benthic habitats, where fish densities were 84% lower than at the warming reef, resulting in shoals that were up to 79% smaller than the Warming and Control reefs. Combined, our data suggest that shoal size mediates behavioural expression between foraging and predator avoidance and that acidification-driven habitat simplification can alter behavioural expression indirectly by reducing fish densities and the formation of large shoals. We conclude that climate change can indirectly modify behavioural expression in shoal-forming fishes through habitat-driven erosion of social structure.

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