Phosphorus release and microbial community alterations in submerged areas of Qinghai Lake

The formation of submerged areas in Qinghai Lake, driven by rising water levels, has resulted in substantial changes in environmental characteristics, phosphorus dynamics, and microbial community composition. Climate-driven hydrological expansion promotes phosphorus remobilization in submerged sediments, necessitating targeted management to mitigate eutrophication risks in Qinghai Lake and analogous alpine ecosystems. This study examines the impacts of submersion on water chemistry, sediment properties, and microbial communities across multiple sites around the lake, including submerged regions, estuaries, and the lake body. Water quality analysis revealed that eutrophication and pollution were more pronounced in flooded areas compared to the lake and estuarine zones, with particulate matter and chlorophyll significantly increased. pH and redox potential measurements revealed that submerged areas exhibited similar characteristics to the lake, with elevated pH and distinct redox shifts. Sediment analysis demonstrated significant changes in particle composition, with coarse sands larger than 0.63 mm accounting for most of the sediment in submerged zones, whereas finer particles (<0.16 mm) predominated in the lake and estuarine sediments, reflecting alterations in sediment texture due to flooding. Phosphorus concentration in water bodies was significantly elevated in submerged areas, with higher levels of both total phosphorus and inorganic phosphorus forms compared to the lake. Moreover, microbial diversity analysis indicated that microbial communities in submerged areas exhibited distinct characteristics from those in the lake and estuary, with greater complexity in co-occurrence networks and shifts in dominant microbial taxa, notably Rhodobacteraceae and Pseudomonadaceae. The abundance of phosphorus-related genes, particularly those involved in phosphate metabolism, was higher in submerged areas, indicating an enhanced microbial contribution to phosphorus cycling. These findings suggest that newly submerged zones not only accelerate internal phosphorus loading but also restructure microbial networks, thereby enhancing the risk of eutrophication. It emphasized shifts in nutrient cycling and microbial dynamics that may affect the overall health and stability of the aquatic ecosystem.