Abstract
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.
Highlights
IntroductionIn the Arctic, and around the world’s oceans, benthic invertebrates play important roles in carbon cycling and remineralization of nutrients (Renaud et al, 2007a), as prey for fish (Eriksen et al, 2020), birds (Merkel et al, 2007), and mammals (Dehn et al, 2007), as well as supporting important fisheries (e.g., the Northern shrimp Pandalus borealis, Garcia, 2007), and subsistence harvestingMeroplankton in the Barents Sea (Rapinski et al, 2018)
In the Arctic, and around the world’s oceans, benthic invertebrates play important roles in carbon cycling and remineralization of nutrients (Renaud et al, 2007a), as prey for fish (Eriksen et al, 2020), birds (Merkel et al, 2007), and mammals (Dehn et al, 2007), as well as supporting important fisheries, and subsistence harvestingMeroplankton in the Barents Sea (Rapinski et al, 2018)
Upper layers in the south consisted entirely of Atlantic Water, except in April when the whole water column was well mixed with characteristics of the Barents Sea Water mass
Summary
In the Arctic, and around the world’s oceans, benthic invertebrates play important roles in carbon cycling and remineralization of nutrients (Renaud et al, 2007a), as prey for fish (Eriksen et al, 2020), birds (Merkel et al, 2007), and mammals (Dehn et al, 2007), as well as supporting important fisheries (e.g., the Northern shrimp Pandalus borealis, Garcia, 2007), and subsistence harvestingMeroplankton in the Barents Sea (Rapinski et al, 2018). The Barents Sea, located in the Atlantic gateway to the Arctic, is home to over 3,000 benthic invertebrate taxa, making it one of the most diverse regions of the Arctic (Piepenburg et al, 2011; Renaud et al, 2015). Most studies on the benthic invertebrates of the Barents Sea have focused on the adult stage (Carroll et al, 2008; Cochrane et al, 2009; Jørgensen et al, 2015; Zakharov et al, 2020). Repeated sampling over the course of a year is required to capture as much of the diversity as possible Such seasonal sampling of Arctic meroplankton has mostly been done in fjordic environments to date (Kuklinski et al, 2013; Stübner et al, 2016; Brandner et al, 2017; Michelsen et al, 2017). A peak in larval abundance coinciding with a peak in local primary production, as occurs in Arctic and Antarctic fjords and coasts (Bowden et al, 2009; Arendt et al, 2013; Michelsen et al, 2017; Presta et al, 2019) as well as in lower latitude regions (Highfield et al, 2010), is often assumed but has not yet been corroborated with seasonally resolved sampling on Arctic shelves
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