Spatial and Temporal Variations in Functional Diversity of Bivalve Molluscs in the Southern Barents Sea

ABSTRACT Bivalve functional diversity patterns in the Barents Sea remain unexamined, presenting a critical knowledge gap. To address this, we conducted a comprehensive study on the diversity, functional structure, and environmental drivers influencing bivalve communities in the southern Barents Sea. We identified 38 bivalve species grouped into three coherent functional assemblages: epifaunal, medium‐sized suspension feeders with fragile shells and lecithotrophic larvae; large, mobile, thick‐shelled suspension feeders with planktotrophic larvae; and small, mobile deposit feeders with fusiform shells and lecithotrophic larvae. Taxonomic richness and Shannon diversity declined poleward, while functional responses were more complex: functional dispersion and divergence decreased with latitude, but functional originality increased, indicating a narrower yet more distinct trait space in northern sites. Multivariate analyses (db‐RDA, GLMs) showed bottom temperature as the dominant structuring factor, followed by long‐term sea surface trend, phytoplankton trend, and depth. Temporal shifts from 2015 to 2019 included increases in deposit feeders and boreal‐affinity species and declines in highly boreal‐Arctic taxa, patterns consistent with ongoing ‘borealization’. Functional group trajectories imply a shift from filtration‐dominated to deposit‐driven benthic processes under Atlantification. The three functional groups are proposed as robust bioindicators for monitoring seafloor responses to climate‐driven changes in temperature, productivity, and water‐mass structure in the Barents Sea.