Meroplankton Diversity, Seasonality and Life-History Traits Across the Barents Sea Polar Front Revealed by High-Throughput DNA Barcoding

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.

Oceanic Fronts Shape Biodiversity of Gelatinous Zooplankton in the European Arctic

“…The two passive fronts of the investigated area have maintained distinct communities of the GZ (Figures 5, 6), in that a portion of taxa were unique for a particular frontal zone, but the few, most abundant ones, were common everywhere. Previous studies from the region arrived at a similar conclusion, like Descôteaux et al (2021) who found that only one-third of meroplankton were shared among both sides of the PF. In any other place in the world's ocean, the presence of the same taxa on both sides of the front would lead to the conclusion of the GZ community exchange across the passive fronts.…”

Origin of marine invertebrate larvae on an Arctic inflow shelf

“…For some, the dispersal stage is short, lasting from minutes to a few hours and resulting largely in recruitment to the parent population, while others disperse for up to several months (Shanks 2009) and, in rare cases, years (Strathmann & Strathmann 2007). In a previous seasonal study in the Barents Sea, most meroplanktonic taxa were found at discrete time points suggesting a larval phase of no more than a few months, though a minority of taxa showed evidence of longer dispersal periods (though still shorter than a year; Descôteaux et al 2021). Those taxa with the potential for longdistance dispersal may be better adapted to finding new habitat following periods of change (Wares & Cunningham 2001, Hardy et al 2011.…”

“…Such a strategy relies on species-level identification of larvae, which has historically been challenging because of the general lack of speciesspecific features at the larval stage for most taxa. New molecular methods, however, now enable reliable identification of planktonic early life stages of benthic invertebrates (Ershova et al 2019, Descôteaux et al 2021.…”

“…This information can provide some indication of which boreal taxa currently have the means of reaching the Barents Sea during their larval stage and therefore may be some of the first to settle once conditions there become favorable for establishment of a new population. Finally, based on our previous observation of a larva of Bohuslania matsmichaeli in the Barents Sea (Descôteaux et al 2021), a nudibranch species otherwise only known from one fjord in southern Norway (Korshunova et al 2018), we performed an additional particle tracking analysis where particles were released from a single point in southern Norway and allowed to drift for 1 yr. We hypothesized that a few of those particles would reach the Barents Sea and Svalbard within 1 yr, though fewer in the northern Barents Sea north of the Polar Front where the influence of the northward-flowing Atlantic Water is comparatively low.…”

Metabarcoding survey of meroplankton communities in the South China Sea and Philippine Sea: Shedding light on inter-basin biogeography in the West Pacific

“…Moreover, the morphological identification of meroplankton is very time-consuming and labor-intensive even for experienced taxonomists (Ershova et al, 2021;Pappalardo et al, 2021). In recent years, with a rapid growth in the number of reference barcodes in public databases as well as the advances in methods specifically designed to barcode meroplankton (Ershova et al, 2019), describing meroplankton into lower taxonomic level has become feasible (Hebert et al, 2003;Descoteaux et al, 2021).…”