Abstract
Despite a large number of studies, a detailed overall picture of benthic communities zonation in the Arctic fjords is currently lacking. Our study aimed to find out whether there is a universal model for the distribution of benthic communities based on the structural features of the fjords. We examined benthic macrofaunal communities in fjords with various environmental settings on the eastern coast of Novaya Zemlya Archipelago, Kara Sea. The material was collected during five cruises undertaken from 2013 to 2016. A total of 50 stations located in the five fjords were taken. In all five fjords, macrofauna had a similar composition assembled from a regional species pool, with a predominance of species tolerant to glacial sedimentation and fluctuations in temperature and salinity. Benthic communities changed consistently along the axis of the bay from the outer slope to the inner parts. Biodiversity and quantitative characteristics of the macrofauna decreased along the environmental gradient related to terrigenous and glacial runoff, consistent with patterns reported in other studies of Arctic glacial fjords. The most impoverished communities were dominated by bivalvePortlandia arcticaand isopodSaduria sabini. At the same time, fjord walls and sills, characterized by low sedimentation rates, strong currents and the presence of ice-rafted debris, were inhabited by patchy distributed benthic communities dominated by species confined to hard substrates. In general, the distribution of communities corresponded to five zones: depleted inner periglacial areas, the upper subtidal belt with stony substrates, deep inner semi-isolated basin, outer non-isolated basins and upper slope transitioning to lower slope. Our study can provide a reference point for monitoring changes in fjord ecosystems in response to climate change and the potential impact of human activities.
Highlights
Global climate change and increased human activity can significantly and unpredictably alter highlatitude ecosystems (Bluhm et al, 2011; Wassman et al, 2011; Polyakov et al, 2020)
Using similarity percentage routine (SIMPER)-analysis, we evaluated the differences in the species composition of the identified communities to answer whether each community is assembled from different species or whether they are similar in species composition but differ only in dominants
If we consider each of the fjords separately, we found two different models explaining macrofauna distribution patterns
Summary
Global climate change and increased human activity can significantly and unpredictably alter highlatitude ecosystems (Bluhm et al, 2011; Wassman et al, 2011; Polyakov et al, 2020). Climate change, including the widespread decrease of outlet glaciers (Vieli et al, 2002; Thomas et al, 2009) and general variability in seasonality and runoff volume, leads to transformation in the hydrological structure of the water column This results in increased stratification and isolation of the inner parts of semi-isolated fjords, and, on the contrary, to increased interaction between weakly isolated bays and the sea, with consequent effects on community faunal patterns (Beuchel et al, 2006; Renaud et al, 2007; Wêsławski et al, 2011). It remains unclear to what extent the ecosystems of fjords and bays are resilient to such impacts? Are there similar spatial patterns across different bays that would allow us to predict the simultaneity and the magnitude of changes, or is every bay unique and will respond in its own way in a changing environment? The study of ecosystems in a variety of fjords (e.g., with different runoff patterns) within the same regional fauna can identify key factors of community formation and, subsequently, predict ecosystem transformation due to climate change and associated shifts in driving factors
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