Application of underwater imagery for the description of upper sublittoral benthic communities in glaciated and ice-free Arctic fjords

Abstract

Complex bottom topography and the presence of oating ice signi cantly complicates the use of traditional sampling methods in Arctic coastal waters, forcing to look for alternative approaches. One such technique is underwater imagery, which has grown in popularity in recent decades based on its effectiveness in hard-to-reach places. We demonstrate that an underwater video mosaic can be a reliable method for comparative analysis of Arctic habitats under the glacier in uence and glacier in uence-free habitats. The lming was carried out in the upper sublittoral (2-65 m) of Hornsund and Isfjorden areas, representing two ice-free and two glaciated bays. Video footage was obtained using an ROV mounted and "drop-down" video cameras and transformed into 148 video mosaics. Based on the lowest possible taxonomic level, 31 biological features (morphospecies) were identi ed and ascribed to benthic functional groups based on their feeding and mobility type. The morphospecies and functional groups were used for the comparative analysis of benthic communities. The study found that melting glaciers have a stronger impact on the structure of benthic communities across geographical areas. Morphological and functional composition of macrofauna re ected conditions in glacier in uence and in uence-free, and turbid water riverine bays. We discovered greater abundances of motile scavengers in glacier in uence bays whereas glacier in uence-free bay had more sessile suspension lters and glacier in uence-free riverine bay was dominated by discreetly motile and deposit feeders. Underwater imagery mosaics have proven to be a fairly reliable tool for eldwork-e cient quantitative characterization of benthic communities in the hard-to-reach Arctic's upper sublittoral. HighlightsCombination of underwater imagery and morphospecies approaches provides su cient data to quantify the dominant macrobenthos forms in the arctic fjords.The morphospecies approach makes it possible to reveal the differences in the functional structure of the benthos in the periglacial and glacier in uence-free areas of the upper sublittoral.Underwater imagery may be recommended for eldwork-e cient assessment of benthos in conditions of complex bottom topography and the presence of oating ice.Consequently, this study highlights a greater in uence of melting glaciers on the structure of benthic communities than across geographical areas