Trait-based analysis of meiobenthic foraminifera in a glacier-influenced Arctic fjord (Kongsfjorden, Svalbard)

Glacier-influenced Arctic fjords are highly dynamic systems where environmental gradients strongly shape benthic communities. We analyzed live meiobenthic foraminiferan assemblages along an inner–outer gradient in Kongsfjorden (Svalbard) using trait-based approaches, RLQ ordination analysis/fourth-corner analysis, and co-occurrence networks to resolve community assembly and functional resilience. Sixty species were classified into 16 traits and 37 functional entities across nine stations. Community structure was governed by a dominant gradient linking coarser, lower organic inner-fjord sediments to finer, organic-enriched outer-fjord habitats. Infaunal, calcareous, and suboxic-tolerant taxa dominated overall, while epifaunal and oxic-associated species were restricted to well-oxygenated substrates, indicating strong habitat filtering. RLQ analysis confirmed significant trait–environment coupling driven by sediment texture, and organic enrichment. Network analysis revealed three distinct species modules, suggesting non-random assembly and habitat-linked functional guilds. Functional diversity indices remained stable across zones despite shifts in species composition, indicating conservation of functional space. However, 73% of functional entities were represented by single species, revealing low redundancy and high vulnerability. These findings highlight strong environmental filtering and limited functional buffering, suggesting that Arctic fjord ecosystems may be more fragile than taxonomic patterns imply under ongoing climate change.