Decadal spatial trends in the feeding-type composition of Arctic deep-sea nematodes at LTER-HAUSGARTEN: A dual classification approach

This study examined functional changes in free-living meiobenthic nematode communities across different water depths and sediment layers over a 20-year period along a bathymetric transect at LTER HAUSGARTEN observatory in the Fram Strait (1200 m, 2500 m, and 4000 m). The focus was on changes in feeding type composition and comparing the performance two different classification systems (Wieser’s and Hodda’s) to assess whether they yield consistent functional interpretations or highlight differences. Published datasets were used to analyse nematode communities, with specimens identified morphologically to the lowest possible taxonomic level and assigned to feeding types. The study investigated how the trophic structure of nematode communities varied over time, with depth, and between sediment layers, aiming to reveal long-term spatio-temporal patterns at LTER-HAUSGARTEN. Microbial feeding nematodes were consistently dominant across all stations and years. While feeding type composition changed significantly over time at each respective station and to a similar strength with water depth, sediment layer had a stronger influence than the temporal variation. Interannual variation of feeding types as well as within-group dissimilarity and dispersion were lowest at the shallowest station and increased with water depth. Similarly, feeding-type composition in the uppermost sediment layer remained most stable over the years and was gradually decreasing with sediment depth. Despite a decline in nematode abundances over time, the overall feeding type composition remained unchanged. Both classification systems produced comparable results, indicating that functional interpretations of nematode communities are robust across classification approaches.