The Izu Ridge off the southern coast of Japan is composed of many seamounts and knolls and is an important fishery ground and hatchery for commercially important fish. As pelagic copepods link lower and higher trophic levels, we investigated the epipelagic copepods in the Izu Ridge using 28S DNA/RNA metabarcoding and microscopic approaches. In comparison with off-ridge regions, a low water temperature and high chlorophyll a concentration were observed in the Izu Ridge, possibly attributed to high levels of nutrients supplied by strong turbulences around the complex topography. We observed unique copepod communities with a large total biomass in the Izu Ridge, owing to the increased dominance of large copepod species. rRNA:rDNA (28S ratio) of these large species mainly showed positive correlations with the chlorophyll a concentration, suggesting a rapid response to the food supply. Migrating copepods were less dominant around the Izu Ridge with a shallow water depth. Higher species diversity and more rare species were detected in the Izu Ridge, which might be maintained by complex environment conditions including temporal and spatial variations in the concentration of chlorophyll a. Thus, the combined approach characterized copepod community structure and diversity supporting the rich pelagic ecosystems in the Izu Ridge.

中文翻译：

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日本南部海岸伊豆海脊表层桡足类群落的 DNA/RNA 元条形码和形态学分析

日本南部海岸的伊豆海岭由许多海山和小丘组成，是重要的渔场和重要商业鱼类的孵化场。由于远洋桡足类将较低和较高的营养水平联系起来，我们使用 28S DNA/RNA 元条形码和显微方法研究了伊豆海脊中的上层桡足类。与山外地区相比，伊豆海岭的水温较低，叶绿素 a 浓度较高，这可能是由于复杂地形周围的强烈湍流提供了高水平的养分。由于大型桡足类物种的优势增加，我们在伊豆岭观察到独特的桡足类群落，其总生物量很大。这些大型物种的rRNA：rDNA（28S比率）主要与叶绿素a浓度呈正相关，表明对食物供应的快速反应。迁移的桡足类在水深较浅的伊豆海脊周围较少。在伊豆海脊中检测到更高的物种多样性和更多的稀有物种，这可能是由复杂的环境条件维持的，包括叶绿素 a 浓度的时空变化。因此，联合方法表征了桡足类群落结构和多样性，支持伊豆海脊丰富的远洋生态系统。