Baletaud Florian, Lecellier Gaël, Gilbert Antoine, Mathon Laëtitia, Côme Jean-Marie, Dejean Tony, Dumas Mahé, Fiat Sylvie, Vigliola Laurent
ENTROPIE, Institut de Recherche pour le Développement (IRD), UR, UNC, IFREMER, CNRS, Centre IRD de Nouméa, 98848 Noumea, New Caledonia, France.
GINGER SOPRONER, 98000 Noumea, New Caledonia, France.
Biology (Basel). 2023 Nov 17;12(11):1446. doi: 10.3390/biology12111446.
Seamounts are the least known ocean biome. Considered biodiversity hotspots, biomass oases, and refuges for megafauna, large gaps exist in their real diversity relative to other ecosystems like coral reefs. Using environmental DNA metabarcoding (eDNA) and baited video (BRUVS), we compared fish assemblages across five environments of different depths: coral reefs (15 m), shallow seamounts (50 m), continental slopes (150 m), intermediate seamounts (250 m), and deep seamounts (500 m). We modeled assemblages using 12 environmental variables and found depth to be the main driver of fish diversity and biomass, although other variables like human accessibility were important. Boosted Regression Trees (BRT) revealed a strong negative effect of depth on species richness, segregating coral reefs from deep-sea environments. Surprisingly, BRT showed a hump-shaped effect of depth on fish biomass, with significantly lower biomass on coral reefs than in shallowest deep-sea environments. Biomass of large predators like sharks was three times higher on shallow seamounts (50 m) than on coral reefs. The five studied environments showed quite distinct assemblages. However, species shared between coral reefs and deeper-sea environments were dominated by highly mobile large predators. Our results suggest that seamounts are no diversity hotspots for fish. However, we show that shallower seamounts form biomass oases and refuges for threatened megafauna, suggesting that priority should be given to their protection.
海山是人们了解最少的海洋生物群落。海山被视为生物多样性热点、生物量绿洲和大型动物的避难所，但与珊瑚礁等其他生态系统相比，其实际多样性仍存在很大差距。我们使用环境DNA宏条形码（eDNA）和诱饵视频（BRUVS），比较了不同深度的五种环境中的鱼类群落：珊瑚礁（15米）、浅海山（50米）、大陆坡（150米）、中海山（250米）和深海山（500米）。我们使用12个环境变量对群落进行建模，发现深度是鱼类多样性和生物量的主要驱动因素，尽管人类可达性等其他变量也很重要。增强回归树（BRT）显示深度对物种丰富度有强烈的负面影响，将珊瑚礁与深海环境区分开来。令人惊讶的是，BRT显示深度对鱼类生物量有驼峰状影响，珊瑚礁上的生物量明显低于最浅的深海环境。鲨鱼等大型捕食者在浅海山（50米）的生物量是珊瑚礁上的三倍。所研究的五种环境显示出相当不同的群落。然而，珊瑚礁和深海环境之间共享的物种以高度移动的大型捕食者为主。我们的结果表明，海山并非鱼类的多样性热点。然而，我们表明较浅的海山形成了生物量绿洲和受威胁大型动物的避难所，这表明应优先保护它们。
