The ratio of species of Atlantic and Pacific origin in modern Arctic fauna of bivalve molluscs

Abstract

The present work aims to estimate the ratio of species of the bivalve molluscs of the Atlantic and the Pacific origin in different geographical and bathymetrical regions of the Arctic basin. Seven shallow-water regions of the Arctic, with depths of 0300 m, (the Norwegian, Barents, Kara, Laptev, East Siberian, Chukchi and Beaufort Seas) and three deep-sea regions with depths exceeding 1000 m (the Norwegian and Greenland Basins, Nansen and Amundsen Basins, Canada Basins) are considered. For the identification of origin we combined fossil records with records of the distribution of living genera and, when possible, used molecular genetic data. The distribution patterns of 265 species from 132 genera were analysed. The share of species of Atlantic origin decreases in marginal Eurasian seas from the Norwegian Sea to the Chukchi Sea, and then increases in the Beaufort Sea. The share of species of Pacific origin is higher only in the Chukchi and Beaufort Seas, the species of the Atlantic and the Pacific origin are equally represented in the East-Siberian Sea. The share of species of the Atlantic origin is much higher in all deep-sea regions. Many taxa of bivalves that dispersed into the Arctic from the North Pacific also penetrated into the North Atlantic. In contrast, most taxa of the Atlantic origin remained in the Arctic Ocean, having stopped at the Bering Strait. Differences between the Arctic boundaries, the Arctic-Atlantic (the Greenland-Iceland-Faeroe Ridge) and the Arctic-Pacific (the Bering Strait) as barriers for dispersal are discussed.

Biogeography of epibenthic assemblages in the central Beaufort Sea

“…Alongside, Atlantic Boreal ARctic decapod and isopod biomass represented an important fraction of the total biomass of the Coastal Zone, the Polar Mixed Layer and the Arctic Halocline. This documents that Atlantic Boreal Arctictaxa can compete with species of other biogeographic affinities on Pacific shelves (Krylova et al 2013;this study).…”

“…Rather, low temperatures prolong larval duration and survival and, thus, Atlantic Boreal Arctic taxa, in contrast, occurred in all water masses across the full depth range of our sampling, again confirming our hypothesis of their broad vertical distribution ranges. The proportion of these taxa of total biomass in deeper water masses (especially Atlantic Water and Canadian Basin Deep Water) increased substantially for mollusks and echinoderms, albeit not for decapods and isopods and agrees with the dominance of Atlantic taxa in the Arctic Basins (Krylova et al 2013;Mironov et al 2013). A similar although less dramatic increase with deeper water masses was observed for Atlantic Boreal Arctic taxon richness in all taxon groups.…”

“…This inflow provides ample opportunity for propagules of deep-water or eurybathic species to spread into the Arctic. Highest faunal similarity between the North Atlantic and Arctic occurs in the Barents Sea region and extending to Svalbard's west coast (Krylova et al 2013), but over geological time North Atlantic species have clearly dispersed all the way into the Canada Basin and the adjacent Beaufort Sea slope with the flow of the Atlantic Water and Arctic Deep Water (Bilyard and Carey 1979;Krylova et al 2013; this study). Notably, however, Atlantic Boreal Arctic taxa also occur, and in some cases even dominate, the shallower water masses on the Beaufort shelf, such as some echinoderm taxa in the Coastal Zone.…”

The Pan-Arctic Continental Slope: Sharp Gradients of Physical Processes Affect Pelagic and Benthic Ecosystems

“…Similarly, fish species richness is higher at the upper slope than adjacent shelf and slower slope in the Beaufort Sea (Majewski et al, 2017) and northern Kara Sea (Dolgov and Benzik, 2017). Biogeographically, the Arctic continental slope seafloor is primarily the domain of species of Atlantic-Arctic affinity, cosmopolitan deep-sea and -at the upper slope -amphiboreal species, while Pacific-Arctic species are largely absent in and below the Atlantic Layer, even on the Amerasian side (benthos: Bilyard and Carey, 1979;Krylova et al, 2013;Zhulay et al, 2019;Ravelo et al, 2020;fish: Dolgov, 2013;Mecklenburg et al, 2016).…”

Bryozoans of the Kara Sea: estimation of species diversity and patterns of biogeographic composition

“…Такой результат был вполне предсказуем, поскольку тихоокеанские виды, встречающиеся в арктическом регионе, изначально рассматриваются как более стенобионтные в связи с тем, что их проникновение в Арктику в позднем плейстоцене ограничивалось мелководностью Берингова пролива (Golikov and Skarlato 1989;Denisenko and Grebmeier 2015). По всей видимости виды мшанок тихоокеанского происхождения, аналогично другим группам донных беспозвоночных (например, Krylova et al 2013), распространились до Карского моря во время одного из резких потеплений, имевших место в позднем плейстоцене -раннем голоцене.…”