Integrating fish taxonomic and functional diversity, co-occurrence networks, and assembly processes to resolve
Yonghua Zhou1, Tianyuan Li1, Wenjing Zhang1
1State Key Laboratory of Marine Environmental Science, Xiamen Key Laboratory of Urban Sea Ecological Conservation and Restoration, College of Ocean and Earth Sciences, Xiamen University, Xiamen, China; National Observation and Research Station for the Taiwan Strait Marine Ecosystem (T-SMART), Xiamen University, Zhangzhou, China.
Abstract:
Fish communities are key components of coastal bay ecosystems, yet the mechanisms governing their seasonal community assembly remain insufficiently understood in dynamic bay systems. Here, we combined 12S rRNA eDNA metabarcoding from 96 water samples collected across four seasons in Xiamen Bay to characterize the seasonality of fish communities and their environmental associations from both taxonomic and functional perspectives, while alsoevaluating community stability and assembly processes. A total of 122 fish species were detected, with α-diversity showing facet-specific seasonality: ACE richness and functional evenness (FEve) peaked in winter, Shannon diversity and Pielou evenness were higher in summer, while functional dispersion (FDis) reached its maximum in autumn. β-diversity partitioning revealed that taxonomic β-diversity was primarily driven by species turnover, whereas functional β-diversity was dominated by nestedness, indicating a nested subset pattern of functional composition despite seasonal species replacement. Consistently, trait composition based on presence-absence data remained broadly stable across seasons, with communities dominated by demersal habitat affiliation, benthivorous feeding, oceanodromous migration, drifting buoyant eggs, warm-water preference, high resilience, and terminal mouth position. Partial redundancy analysis (pRDA) further indicated that temperature, salinity and pH were the main drivers of seasonal variation in taxonomic composition, whereas total phosphorus and salinity showed stronger associations with functional composition. Network analysis indicated higher structural stability in winter and spring, in contrast to summer and autumn. Additionally, stochastic processes, particularly ecological drift and dispersal limitation, played a dominant role in shaping fish communities. Overall, this study provides a seasonal perspective on fish community structure, functional organization, and assembly processes in coastal bays, offering a scientific basis for biodiversity monitoring and fisheries management.
