Under-ice observations by trawls and multi-frequency acoustics in the Central Arctic Ocean reveals abundance and composition of pelagic fauna

Abstract

The rapid ongoing changes in the Central Arctic Ocean call for baseline information on the pelagic fauna. However, sampling for motile organisms which easily escape vertically towed nets is challenging. Here, we report the species composition and catch weight of pelagic fishes and larger zooplankton from 12 trawl hauls conducted in ice covered waters in the Central Arctic Ocean beyond the continental slopes in late summer. Combined trawl catches with acoustics data revealed low amounts of fish and zooplankton from the advective influenced slope region in the Nansen Basin in the south to the ice-covered deep Amundsen Basin in the north. Both arctic and subarctic-boreal species, including the ones considered as Atlantic expatriate species were found all the way to 87.5o N. We found three fish species (Boreogadus saida, Benthosema glaciale and Reinhardtius hippoglossoides), but the catch was limited to only seven individuals. Euphausiids, amphipods and gelatinous zooplankton dominated the catch weight in the Nansen Basin in the mesopelagic communities. Euphausiids were almost absent in the Amundsen Basin with copepods, amphipods, chaetognaths and gelatinous zooplankton dominating. We postulate asymmetric conditions in the pelagic ecosystems of the western and eastern Eurasian Basin caused by ice and ocean circulation regimes.

Fluctuating Atlantic inflows modulate Arctic atlantification

“…4E). An increased influence of the Barents Sea may cause the eastern Eurasian Basin to be more productive and provide more suitable living conditions for subarctic-boreal species than its western part ( 51 ), which is consistent with recent observations ( 50 ). Improved knowledge of asymmetric conditions in the pelagic ecosystems of the western and eastern Eurasian Basin is imperative to properly understand and manage the central Arctic Ocean fisheries agreement established in 2021.…”

Investigating pelagic biodiversity and gelatinous zooplankton communities in the rapidly changing European Arctic: An eDNA metabarcoding survey

“…finmarchicus , and Oithona spp. This is in line with morphological studies in the same area (Darnis & Fortier, 2014; Gluchowska, Dalpadado et al., 2017; Ingvaldsen et al., 2023; Kosobokova et al., 2011), as well as findings in the Chukchi Sea (Questel et al., 2021). We recovered sequences from holoplanktonic (e.g., physonect siphonophores and calanoid copepods) and benthic taxa (e.g., bryozoans and polychaete worms), including many with meroplankton life stages (e.g., echinoderms and poriferans).…”

“…They serve major ecosystem roles as predators and are important in pelagic-benthic coupling and vertical carbon export (Jaspers et al, 2023;Lebrato et al, 2012Lebrato et al, , 2013, particularly when occurring in high numbers (aggregations or blooms). Recent studies have shown poleward expansions of the distribution ranges of boreal species, e.g., for the large scyphozoan Periphylla periphylla around Svalbard and in the Nansen Basin (Geoffroy et al, 2018;Ingvaldsen et al, 2023). Additionally, increased abundances of the arcto-boreal hydrozoan Aglantha digitale have been found in warmer water masses in the North Atlantic (Haberlin et al, 2019) and in Atlantic water masses in Fram Strait (Mańko et al, 2020), where it is predicted to become a dominant species as the Arctic warms (Mańko et al, 2020;Pantiukhin et al, 2023a).…”