In many species of marine benthic invertebrates, a planktonic larval phase plays a critical role in dispersal. Very little is known about the larval biology of most species, however, in part because species identification has historically been hindered by the microscopic size and morphological similarity among related taxa. This study aimed to determine the taxonomic composition and seasonal distribution of meroplankton in the Barents Sea, across the Polar Front. We collected meroplankton during five time points seasonally and used high-throughput DNA barcoding of individual larvae to obtain species-level information on larval seasonality. We found that meroplankton was highly diverse (72 taxa from eight phyla) and present in the Barents Sea year-round with a peak in abundance in August and November, defying the conventional wisdom that peak abundance would coincide with the spring phytoplankton bloom. Ophiuroids, bivalves and polychaetes dominated larval abundance while gastropods and polychaetes accounted for the bulk of the taxon diversity. Community structure varied seasonally and total abundance was generally higher south of the Polar Front while taxon richness was overall greater to the north. Of the species identified, most were known inhabitants of the Barents Sea. However, the nemertean Cephalothrix iwatai and the brittle star Ophiocten gracilis were abundant in the meroplankton despite never having been previously recorded in the northern Barents Sea. The new knowledge on seasonal patterns of individual meroplanktonic species has implications for understanding environment-biotic interactions in a changing Arctic and provides a framework for early detection of potential newcomers to the system.

中文翻译：

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高通量DNA条形码显示巴伦支海极地前线的浮游生物多样性，季节性和生活史特征

在许多海洋底栖无脊椎动物中，浮游幼体阶段在扩散中起关键作用。对于大多数物种的幼虫生物学知之甚少，部分原因是由于历史上相关物种的微观大小和形态相似性阻碍了物种识别。这项研究旨在确定极地前锋在巴伦支海的浮游生物的分类学组成和季节性分布。我们在季节性的五个时间点收集了浮游生物，并使用单个幼虫的高通量DNA条形码获得了有关幼虫季节性的物种水平信息。我们发现，浮游生物种类繁多（八个门类共72个分类单元），全年存在于巴伦支海，在8月和11月的丰度最高，打破了传统的常识，即峰值丰度与春季浮游植物的花期重合。幼虫的丰富度以阿片类，双壳类和多毛类为主，而腹足类和多毛类则占整个分类群的大部分。群落结构随季节而变化，总的丰度通常在极地线以南较高，而分类单元丰富度总体在北部较高。在确定的物种中，大多数是巴伦支海的已知居民。然而，尽管以前从未在北部的巴伦支海记录过，但在浮游生物中，nemertean Cephalothrix iwatai和易碎的Ophiocten gracilis星是丰富的。