| Summary: | The melting and retreat of Arctic glaciers are prime consequences of climate change in the European Arctic, Spitsbergen. The coastal seascapes are freeing from glacials at a rate of 500 m per year, whereas the duration of coastal ice has decreased from 7–9 to 2–3 months in the late winter. Deglaciation of Spitsbergen causes the formation of new habitats not previously accessible. There were observed changes in increased biomass and biodiversity, as well as sublittoral communities moving towards shallower waters, where ice scouring was a limiting factor. Yet, enhanced melting and retreat of the glaciers cause intensive sedimentation of mineral matter and freshwater inflow into the fjords. As a result, macrophyte expansion lowers as a euphotic zone decreases and larger sedimentation rates favor suspension-feeding over depositfeeding organisms. The aim of this study was to compare the structure of benthic communities of upper sublittoral near the retreating glaciers with ice-free areas. An underwater video survey was carried out during 2018–2019 summer months in four bays: Adriabuka and Burgerbukta in Hornsund, and Gipsvika and Borebukta in Isfjorden. In total, 2.8 h of video material were collected using a remotely operated vehicle and a “drop-down” video camera from the polar yacht Magnus Zaremba and RV Oceania. Video footage was transformed into 148 video mosaics that were used for visual analysis. Overall, 43 biological features were identified to the lowest possible taxonomic level. The results showed that benthic communities near the glacial mainly consist of mobile fauna and tube dwellers with relatively low diversity, whereas in ice-free areas communities are more diverse and consist of mobile, sessile, and burrowing benthos. Underwater imagery proved to be a reliable method for the characterization of benthic communities in the upper sublittoral, where access for large research vessels is limited due to floating ice and steep slopes.
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