Abstract

Simple SummaryBryozoans 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 Walkeria uva 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.

Highlights

  • Interactions of the cold Arctic and warm Atlantic waters is the main feature of the Barents Sea [1] making this large marine ecosystem the most productive shelf region of the Arctic [2,3] and supporting abundant stocks of fish and shellfish [4,5,6]

  • The highest wave flow intensity was registered at open Stations 4 and 5 while zero wave intensity occurred at the head of Dalnezelentskaya and Yarnyshnaya Bays (Stations 7 and 9)

  • Bryozoan community structure at two adjoining sites in the intertidal zone of the Barents Sea was linked to local environmental variables, including biogenic element concentrations, silicates, oxygen, wave flow intensity, temperature, and salinity in the period of warming in the Arctic

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Summary

Introduction

Interactions of the cold Arctic and warm Atlantic waters is the main feature of the Barents Sea [1] making this large marine ecosystem the most productive shelf region of the Arctic [2,3] and supporting abundant stocks of fish and shellfish [4,5,6]. The Barents Sea, like other Arctic regions, is being influenced by the effects of global warming and we are witnessing significant shifts in the ecosystem components and processes including strong salinification of the upper Eurasian Basin, attendant reductions in stratification, and altered nutrient fluxes and primary production [7,8,9]. Bryozoan colonies or zoariums are diverse in form, ranging from flat encrusting habits, where all zooids adhere to a hard substrate, to erect, rigid colonies with foliaceous, arborescent, or fenestrate shapes. Others are free-living with bun- or disc-shaped forms [18]

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