Multiple environmental factors drive the functional dimension of fish communities in the Central East China Sea.

A study of fish functional diversity based on trait-environment relationships offers new insights into comprehending the community structure of fish within marine ecosystems. The East China Sea is one of the most productive marine regions in China, and its fish communities are facing multiple pressures, including environmental changes, human activities, and habitat degradation. This study aims to investigate the functional α- and β-diversity of fish in the region, identify the environmental factors driving these variations, and explore how fish functional traits respond to these factors, using fish survey data from the central part of the Sea in 2016 and 2020, three functional α-diversity indices (functional richness, functional evenness, and functional divergence) and three functional β-diversity indices (functional β-diversity, functional turnover, and functional nestedness) were determined, as well as their comparisons. Random forest models were adopted to explore the influence of environmental factors on fish functional diversity, and RLQ (a combined analysis of environmental variables table R, species occurrence table L, and functional traits table Q) combined with the fourth-corner method was used to detect correlations between fish functional traits and environmental factors. Compared with 2016, functional richness significantly decreased in 2020, whereas functional divergence significantly increased. Functional β-diversity and functional turnover showed an increasing tendency from 2016 to 2020, and functional turnover and functional nestedness exhibited similar contributions to functional β-diversity across both periods. Chlorophyll a and sea surface temperature were the most influential variables, positively to functional divergence, functional β-diversity, and functional turnover but negatively to functional richness. Traits benthic water column preference and sedentary preference were closely related to lower values of Chlorophyll a, sea surface temperature, and pH. Under the current dramatic environmental changes, sedentary and benthic species were likely to be more vulnerable to exterior disturbances, which highlighted the need to incorporate sedentary and benthic fish into coastal management and conservation strategies.