Ecological and spatial factors shaping abyssal and hadal peracarid crustacean communities in the eastern Aleutian Trench (NE Pacific)

The abyssal and hadal deep sea, characterised by high pressures, low temperatures, and limited light availability, hosts a remarkable diversity of organisms that have adapted to these harsh conditions. Despite its vastness, the deep sea remains relatively unexplored, and our understanding of the factors governing its community composition, diversity, and abundance is still limited. In this study, we aim to elucidate the various factors that contribute to shaping deep-sea peracarid communities and provide insights into their ecological dynamics. Benthic material was collected during the AleutBio (SO293) expedition aboard the RV Sonne from July 24th to September 6th, 2022 in the Northeast Pacific Ocean. A total of 19 samples were collected with an epibenthic sledge at depths ranging from 3,517 to 7,254 m. In total, 5,400 peracarid specimens were collected, with amphipods and isopods being the most dominant groups, accounting for 35 % and 36 % (1,546 and 1,591 ind./1,000 m haul) respectively, followed by cumaceans and tanaidaceans, which each contributed 13 % of the total peracarid composition (584 and 556 ind./1,000 m). Hierarchical cluster analysis and non-metric multidimensional scaling (nMDS) revealed dissimilarity in the abundance patterns between hadal and abyssal stations, highlighting significant variation in assemblage structure. Further Redundancy Analysis (RDA), showed that depth was the primary environmental factor driving peracarid abundance across the stations. The results contribute valuable insights into the distribution patterns of peracarids in the Aleutian Trench region and underscores the need for further investigations into the role of environmental variables in structuring deep-sea communities.