Table_2_Depth-Dependent Structuring of Reef Fish Assemblages From the Shallows to the Rariphotic Zone.docx

Shallow coral reef ecosystems worldwide are affected by local and global anthropogenic stressors. Exploring fish assemblages on deeper reefs is therefore important to examine their connectivity, and to help understand the biodiversity, ecology, distinctiveness, evolutionary history and threats in this sparsely studied environment. Conducting visual surveys on the Bermuda slope and a nearby seamount at depths from 15 to 300 m, we document decreasing fish biomass and diversity with increasing depth. Fish assemblages were primarily depth-stratified, with distinct suites of species inhabiting shallow (<30 m depth) and upper (60 m) and lower (90 m) mesophotic coral ecosystems, and confirming the presence of a distinct rariphotic (∼150–300 m) assemblage. We also report evidence of anthropogenic pressures throughout our surveyed depths. Our results highlight the novelty of deeper reef fish faunas, therefore suggesting limited applicability of the deep reef refuge hypothesis, and showcase the vulnerability of deep reefs to targeted fishing pressure and invasive species.

全球范围内的浅海珊瑚礁生态系统均受到局地与全球性人为胁迫因素的影响。因此，对深水礁体上的鱼类群落开展研究，对探究其连通性，以及认知这一研究程度较低的生境中的生物多样性、生态学特征、独特性、演化历史与威胁因素均具有重要意义。我们在百慕大斜坡及附近一座海山的15至300米水深范围内开展水下目视调查，记录到鱼类生物量与物种多样性随水深增加而逐渐下降的规律。鱼类群落在深度上呈现显著分层：浅水区（水深<30米）、中光层珊瑚礁生态系统（mesophotic coral ecosystems）的上层（60米）与下层（90米）分别栖息着特征鲜明的物种类群，同时证实了稀深带鱼类群落（rariphotic assemblage，约150–300米水深）的存在。我们还在所有调查水深范围内发现了人为压力的相关证据。本研究结果凸显了深水礁鱼类区系的独特性，因此表明深礁避难假说（deep reef refuge hypothesis）的适用范围较为有限，同时揭示了深水礁体面临针对性捕捞压力与入侵物种威胁的脆弱性。