Response of trophic structure and isotopic niches of the food web to flow regime in the Yellow River estuary

Abstract

Variations in the flow regime lead to changes in the spatial and temporal distributions of nutrients entering the estuary area from the river, which causes corresponding changes in the trophic structure of the estuarine food web and ultimately affects the entire ecosystem. Therefore, studying the responses of estuarine food webs to changes in upstream water and sediment conditions is of great significance for protecting the biodiversity, stability, and functional integrity of estuarine ecosystems. This study focused on the world-famous sandy river, the Yellow River, and the south and north shores of the Yellow River estuary and selected sample areas with different environmental characteristics. Typical species were sampled and measured for carbon- and nitrogen-stable isotopes in the wet and dry seasons, respectively. Based on community indicators of stable isotopes, the trophic structure patterns of the aquatic ecosystem in the Yellow River estuary at different times and spaces were described. The results showed that the north shore area had greater trophic diversity and lower trophic redundancy than the south shore area. This kind of gap was more obvious in the wet season when water was abundant than in the dry season. The south shore area with lower aquatic productivity had greater reliance to input from terrestrial organic matter than the north shore area. The increase in terrestrial material input during the wet season increased the carbon-stable isotope value of the south shore food web and changed the basic food sources. The north shore food web, which did not depend on a single food source, had more abundant organic matter sources. The trophic diversity increased in the wet season, but the trophic redundancy was reduced. Our research suggests that the trophic structure patterns of estuarine ecosystems vary with the hydrological regime and environmental conditions, especially turbidity, which greatly affect the stability of estuarine ecosystems.