Hierarchical approach reveals site-scale drivers of nematode assemblages on the west coast of Korea

This study was performed to assess the spatial variability of free-living marine nematode assemblages in tidal flats along the west coast of Korea to understand natural and anthropogenic factors shaping nematode community structures. Sediment and nematode samples were collected in August and September 2023 using a hierarchical sampling design comprising three regions, each with three sites (W1-W9), and three patches within each site. Significant differences in nematode density, diversity, and community composition were observed at smaller spatial scales (the site and patch levels), whereas no significant variation was detected at the regional scale. A distance-based multivariate multiple regression analysis revealed that sediment composition, total nitrogen, and arsenic concentration were key environmental variables influencing nematode communities. These findings suggest that free-living nematodes are sensitive indicators of small-scale environmental heterogeneity and can provide a useful basis for assessing benthic ecosystem variability across Korean tidal flats.