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 floating ice significantly complicate 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 influence and glacier influence-free habitats. The filming 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 identified and ascribed to benthic functional groups based on their feeding and mobility type. The morphospecies and functional groups were used for the comparative analysis to reveal the ecologically meaningful differences in benthic community structure in different Arctic benthic habitats. We discovered greater abundances of motile scavengers in glacier-influenced bays whereas glacier influence-free bay had more sessile suspension filters and glacier influence-free riverine bay was dominated by discreetly motile and deposit feeders. Underwater imagery mosaics have proven to be a fairly reliable tool for fieldwork-efficient quantitative characterization of benthic communities in the hard-to-reach Arctic's upper sublittoral.