Phosphorus release from newly inundated soils and variation in benthic algal nutrient limitation induced by rising water levels of Qinghai Lake, China

The mobilization of internal phosphorus (P) plays a crucial role in transitioning nutrient limitations within lake ecosystems. While previous research has extensively examined P release in littoral zones influenced by fluctuating water levels, there is a paucity of studies addressing the implications of sustained water level rise in this context, particularly as it pertains to nutrient limitations in benthic algae. To address this gap, we conducted an integrated study in Qinghai Lake. In the field sampling and microcosm experiment, we found that P concentrations are elevated in areas subjected to short-term inundation compared to those enduring prolonged inundation, primarily due to the dissolution of sedimentary P fractions. The results of nutrient diffusing substrata (NDS) bioassays indicated that benthic algae in Qinghai Lake displayed either P limitation or NP co-limitation. The transition from P limitation to NP co-limitation suggested that internal P release may serve to ameliorate nutrient limitations in benthic algae. This phenomenon could potentially contribute to the proliferation of Cladophora in the littoral zones of Qinghai Lake, thereby posing long-term implications for the lake's aquatic ecosystem, particularly under conditions of sustained water level rise.