Anthropogenic regulation governs nutrient cycling and biological succession in hydropower reservoirs

Hydropower plays an important role in the supply of renewable energy, but it also exerts a great influence on the river continuum. Understanding nutrient cycling and microbial community succession in hydropower reservoirs is key to weighing hydroelectric pros and cons. However, the underlying control mechanisms are still not well known, especially with respect to the impacts of hydrological conditions. Based on a comprehensive survey of hydropower reservoirs along the Wujiang River in SW China and an integration of published data, we found that reservoir physicochemical and biological stratifications and planktonic microbial community assembly were synergistically evolving, and reservoir hydraulic load (i.e., mean water depth per unit retention time) was a key factor controlling the strength of stratifications, CO2 and N2O fluxes, nutrient retention efficiency, and bacterioplankton diversity. Hydraulic loads are artificially designed for hydropower reservoirs, and nutrient cycling and biological succession in reservoirs are thus governed by anthropogenic regulation. This study provides a theoretical basis to mitigate the environmental impacts of hydropower dams by regulating reservoir hydraulic load.

Automated summary

The study reveals that the hydraulic load of hydropower reservoirs is a key factor influencing stratification, gas fluxes, nutrient retention efficiency, and microbial diversity. Regulating the hydraulic load can mitigate the environmental impacts of hydropower dams.