Spatio-seasonal variations in functional trait composition and diversity patterns of marine fish communities in coastal waters

Despite the consensus that the distribution of functional traits within a community provides insights into community assembly and maintenance mechanisms, few studies have explored spatio-seasonal variations in the functional patterns of marine fish communities. Seven functional traits within the context of 2 distinct groups—habitat use and trophic niche—were selected to assess functional richness (FRic), functional evenness (FEve), and functional dispersion (FDis) across various spatio-seasonal scales. Community-weighted mean redundancy analysis (CWM-RDA) was used to identify the impact of environmental factors on dominant traits. We found seasonal and spatial variations in dominant traits of the fish community, notably influenced by the latitudinal-depth gradient (from shallower stations in the north to deeper stations in the south), east-west (longitudinal) dynamics, and temperature gradient. Latitude was negatively correlated with the CWM values of most functional trait categories. FRic showed more pronounced seasonal variations than other indices, with higher values observed in autumn. Fish assemblages displayed more similarity in functional traits in winter than in other seasons, with lower FRic, higher FEve, and lower FDis. Overall, our findings illustrate that fish assemblages undergo continuous formation and dissolution across different seasons and zones, resulting in various forms of functional diversity patterns.