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Simple Summary: The warming of Arctic regions has led to an increase in extended ice-free periods in the continental shelf of the northeastern Barents Sea. A study on the Makarov Strait in the southwestern part of the St. Anna Trough in autumn 2019 investigated the effect of this process on the structure and functioning of benthic communities. It was found that the biodiversity and structure of local macrozoobenthos were connected with the duration of ice-free periods because this variable influenced vertical carbon flux and was found to be the primary predictor for faunal abundance and diversity indices. Two faunal groups were identified, corresponding to short and long open-water periods. Our results may have important implications for the conservation and monitoring of this region. The continental shelf of the northeastern Barents Sea is presently experiencing a weak influx of Atlantic water from the west. In recent times, warming in Arctic regions has led to an increase in extended ice-free periods in this area, instead of significantly elevating water temperatures. The implications of this phenomenon on the structure and functioning of benthic communities were investigated during the autumn of 2019 within the Makarov Strait, located in the southwestern part of the St. Anna Trough. The macrozoobenthic communities exhibited a clear connection with the duration of ice-free periods. This variable influenced a vertical carbon flux, which subsequently served as the primary predictor for faunal abundance and diversity, as demonstrated by redundancy and correlation analyses. Two faunal groups were identified, corresponding to short and long open-water periods. Both groups had similar alpha diversity (65 ± 6 and 61 ± 9 species per station) and biomasses (39 ± 13 and 47 ± 13 g m−2) but displayed differing abundances (1140 ± 100 vs. 4070 ± 790 ind. m−2) and other diversity indices. We observed a decline in the proportion of polychaetes, accompanied by an increase in the proportion and diversity of bivalves, as well as a rise in the abundance of infaunal species, sub-surface deposit feeders, and mobile suspension feeders, in response to the increasing vertical carbon flux. The potential increase in anthropogenic pressures related to oil development in the northeastern Barents Sea highlights the importance of our study for conservation and monitoring efforts in the region. [ABSTRACT FROM AUTHOR]

Franz Josef Land is located in the northern region of the Barents Sea and is subjected to the constant influx of cold Arctic water. Although this area is difficult to access, several benthic surveys have been conducted to evaluate the spatial patterns and community structure of the local fauna. However, there is a lack of information regarding the structure of bryozoan communities in this region during the ongoing climate change period. Therefore, we studied the species composition and spatial distribution of bryozoan diversity and biomass at 17 stations sampled by a 0.1 m2 Van Veen grab in the southern region of the archipelago between 2006 and 2008. We found 151 bryozoan species, with Turbicellepora incrassata , Celleporina ventricosa , Leieschara subgracilis , Porella compressa , and Escharopsis lobata being the most prevalent. The proportions of Boreo-Arctic, Arctic, and boreal taxa were 55.6%, 35.8%, and 8.6%, respectively. Twenty-two species were recorded for the first time in this region, including seven boreal species (31.7% of their total number) probably as a result of climate change in the Arctic. Alpha-diversity ranged from 3 to 76, with a mean value of 26 species. Bryozoan biomass ranged from 0.1 to 742 g m−2, averaging 139.4 g m−2. Cluster analysis revealed three groups of stations following the depth gradient and sediment composition in shallow and deep waters. The primary environmental drivers of bryozoan communities were depth and temperature (negative association) and contents of stones and shells (positive link). Our research addresses crucial knowledge gaps, such as benthic diversity shifts during the climate change period and the impact of ecological factors on community structure. [Display omitted] • Species of Boreo-Arctic origin dominated the community. • Twenty-two species were recorded for the first time in the region. • Bryozoan biomass was higher compared to other parts of the Barents Sea. • Depth, temperature, and sediment type were the most important drivers of the fauna. [ABSTRACT FROM AUTHOR]

Simple Summary: Bryozoans are colonial organisms that are usually found attached to solid substrata. They are known to be common components of benthic communities from the littoral zone to deep-sea areas. Despite the long history of bryozoan research in the Barents Sea, intertidal communities of this group are less studied than those at open water sites. This is particularly true for the assessment of the role of environmental factors in diversity and biomass fluctuations of Arctic bryozoan assemblages. We collected bryozoans at two adjoining coastal sites in the southern Barents Sea and detected range extension of one boreal species, which reflects a warming trend and borealization of the benthic fauna in the region. In general, the total bryozoan biomass and diversity were lower than in deep-water sites of the sea. Salinity and temperature were found to be the main predictors of bryozoan species richness and biomass, respectively, with more diverse and abundant assemblages occupying habitats with higher salinity and lower temperature. Our findings are in accordance with a general opinion that benthic communities of the coastal Barents Sea are mainly controlled by temperature regime fluctuations and freshwater runoffs. There is a lack of knowledge regarding the modern status of intertidal bryozoan communities in the coastal Barents Sea. Here, we studied species composition, richness, and biomass of bryozoans in Yarnyshnaya and Dalnezelenetskaya Bays, both located in the eastern part of the Kola Peninsula (Barents Sea), in summer. Species composition and biodiversity were consistent with previous research but the record of the ctenostome bryozoan Walkeriauva is the first for the region indicating eastward range expansion of this species associated with climate forcing in the Arctic. Mean biomass was relatively low accounting for 2.25 ± 0.95 g·m−2. The most common species were Eucratea loricata, Harmeria scutulata, Crisia eburnea, and Cribrilina cryptooecium averaging 96% of the total biomass. Cluster analysis delineated two distinct groups of stations, one with true marine conditions and another with brackish water conditions. Redundancy analysis revealed that bryozoan diversity was strongly associated with salinity fluctuations being extremely low at brackish water sites. In contrast, water temperature was found to be a significant contributor to biomass with the lowest values found at warmer waters probably owing to the predominance of Boreo-Arctic species which prefer lower-temperatures. Other hydrological variables (dissolved organic matter, silicates, and oxygen) were consistent with usual summer values and had no significant effects on the bryozoan assemblages. Our study provides a reference point for further biodiversity studies in changing marine ecosystems of the Arctic region. [ABSTRACT FROM AUTHOR]