Evolution of aquatic food web structures under cascade hydropower development in the upper yellow river

Area of Science:

• Ecology
• Environmental Science
• Fisheries Science

Background:

• Cascade hydropower development significantly alters river hydrology and habitats.
• These alterations impact fish community assembly, food web structure, and ecosystem stability.
• Understanding these changes is critical for managing regulated river ecosystems.

Purpose of the Study:

• To investigate temporal changes in fish food webs within the Longyangxia-Liujiaxia cascade system in the upper Yellow River.
• To quantify changes in food web complexity and stability across different hydropower development phases.
• To assess the trade-offs between complexity and stability under hydropower regulation and invasive species presence.

Main Methods:

• Integrated historical records with contemporary field surveys for temporal analysis.
• Developed phase-specific food web models to quantify network complexity (species richness, number of links, link density, connectance).
• Assessed food web stability using metrics like mean trophic level, omnivory, modularity, and quasi-stationary state.

Main Results:

• Cascade development favored resident species and increased habitat heterogeneity, leading to non-native species invasions.
• Non-native species restructured trophic interactions, increasing species richness and topological complexity.
• Despite increased complexity metrics (links, density, trophic levels, omnivory, modularity), the quasi-stationary state declined, indicating reduced local stability.

Conclusions:

• Hydropower development and invasive species create complexity-stability trade-offs in river ecosystems.
• Intensive hydropower regulation impacts ecosystem resilience.
• Integrated management strategies are needed to balance engineering impacts, invasive species control, and ecological resilience.