Diel partitioning of animals within ecological communities is widely acknowledged, yet rarely quantified. Investigation of most ecological patterns and processes involves convenient daylight sampling, with little consideration of the contributions of nocturnal taxa, particularly in marine environments. Here we assess diel partitioning of reef faunal assemblages at a continental scale utilizing paired day and night visual census across 54 shallow tropical and temperate reefs around Australia. Day–night differences were most pronounced in the tropics, with fishes and invertebrates displaying distinct and opposing diel occupancy on coral reefs. Tropical reefs in daytime were occupied primarily by fishes not observed at night (64% of all species sighted across day and night, and 71% of all individuals). By night, substantial emergence of invertebrates not otherwise detected during sunlit hours occurred (56% of all species, and 45% of individuals). Nocturnal emergence of tropical invertebrates corresponded with significant declines in the richness and biomass of predatory and herbivorous diurnal fishes. In contrast, relatively small diel changes in fishes active on temperate reefs corresponded to limited nocturnal emergence of temperate invertebrates. This reduced partitioning may, at least in part, be a result of strong top‐down pressures from fishes on invertebrate communities, either by predation or competitive interference. For shallow reefs, the diel cycle triggers distinct emergence and retreat of faunal assemblages and associated trophic patterns and processes, which otherwise go unnoticed during hours of regular scientific monitoring. Improved understanding of reef ecology, and management of reef ecosystems, requires greater consideration of nocturnal interactions. Without explicit sampling of nocturnal patterns and processes, we may be missing up to half of the story when assessing ecological interactions.

中文翻译：

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鱼类和无脊椎动物群落在热带珊瑚礁上表现出比温带珊瑚礁更大的昼夜分割


生态群落内动物的 Diel 分区被广泛承认，但很少被量化。对大多数生态模式和过程的研究都涉及方便的日光采样，很少考虑夜间类群的贡献，特别是在海洋环境中。在这里，我们利用澳大利亚 54 个浅热带和温带珊瑚礁的配对昼夜视觉普查，在大陆尺度上评估了珊瑚礁动物群落组合的 diel 分区。昼夜差异在热带地区最为明显，鱼类和无脊椎动物在珊瑚礁上表现出明显且相反的 diel 占据。白天的热带珊瑚礁主要被夜间未观察到的鱼类占据（占白天和黑夜观察到的所有物种的 64%，占所有个体的 71%）。到了晚上，在阳光照射下没有检测到的无脊椎动物大量出现（占所有物种的 56%，占个体的 45%）。热带无脊椎动物的夜间出现与掠食性和草食性昼夜鱼类的丰富度和生物量的显著下降相对应。相比之下，活跃在温带珊瑚礁上的鱼类的 diel 变化相对较小，对应于温带无脊椎动物的有限夜间出现。这种减少的分区可能至少部分是由于鱼类对无脊椎动物群落施加的自上而下的巨大压力，无论是通过捕食还是竞争性干扰。对于浅水珊瑚礁，diel 循环会触发动物群落组合以及相关的营养模式和过程的不同出现和后退，否则在定期科学监测的数小时内不会注意到这些。提高对珊瑚礁生态学的理解和对珊瑚礁生态系统的管理，需要更多地考虑夜间相互作用。 如果不对夜间模式和过程进行明确的采样，我们在评估生态相互作用时可能会错过多达一半的故事。