Seasonal variation in the functional structure of demersal fish communities and response to the environmental changes in the Pearl River Estuary, China

Abstract

Estuaries are one of the most important ecosystems with high biological productivity. They connect freshwater and marine ecosystems, and the fish community assemblages face intense environmental changes, so estuarine fish communities have unique ecological characteristics. With the increase of human activities and the discharge of pollutants, the pressure on the ecosystem of the Pearl River Estuary (PRE) is intensifying, and its ecosystem functions and services are inevitably affected. To better understand the functional structure of the fish community in the PRE and its response to environmental changes, we analyzed the trait composition of the community and its relationships to environmental factors based on 10 functional traits of 130 fish species collected in the PRE during the summer and winter of 2020–2021. In addition, we built a multi-dimensional functional space to visualize the overall functional structure of the PRE and explore the seasonal variation of the selected traits in the functional space. Our findings suggest that the functional traits of the fish communities in the PRE were mainly affected by temperature, dissolved oxygen, chlorophyll-a, and depth. Among them, the effects of dissolved oxygen, temperature, and chlorophyll-a on CWM traits were reflected in seasonal differences, while the effects of depth were reflected in spatial differences. We also found the main trait categories that occupied the most functional space and contributed the most to the seasonal differences in functional space. The results of this study are significant for understanding the seasonal variation of the functional structure in the PRE and how environmental gradients drive the functional traits of fish communities, and also provide insights for effective ecosystem-based management in the PRE.