Taxonomic and functional diversity patterns of nematode assemblages were examined in a trawl-restricted gulf (Pagasitikos Gulf, Central Aegean Sea). The goal was to determine the drivers that structure nematode communities and examine whether functional approaches add information beyond taxonomic patterns. Samples were taken from 36 stations across three nutrient zones and genus-level abundances were combined with categorical traits to calculate taxonomic and functional indices. Environmental drivers were examined using multivariate analyses, including RLQ ordination, variance partitioning, null models, and generalized additive models of functional groups. Genus richness, Shannon diversity, Rao’s Q, functional dispersion, functional richness and maturity index differed among zones and these differences remained significant after accounting for depth. The lower external zone contained 76.71% of the total genus pool and 82.69% of the total functional entity pool, whereas the upper external zone showed the lowest representation (27.4% of genera and 30.77% of functional entities). Functional space occupancy was high in both the inner gulf (92.89%) and lower external zone (90.63%), but lower in the upper external zone (70.74%). RLQ showed poor fit between single traits and abiotic variables, whereas trait complexes were better responses to environmental gradients. The upper external zone exhibited the worst ecosystemic condition, associated with nematode genera that belonged to trophic group 2A, heavily annulated cuticle, capsulated head and very complex amphids. These findings show that ecological zonation captures community structure better than depth alone and that functional patterns largely mirror taxonomic structure, while providing additional context on redundancy, vulnerability, and the distribution of ecological strategies. The combination of moderate functional redundancy and localized functional vulnerability suggests uneven resilience across zones, with lower-quality areas showing reduced functional representation and increased sensitivity to disturbance. This combined taxonomic–functional approach strengthens benthic assessment in coastal systems.
Voulgaris et al. (Fri,) studied this question.