黄土高原多泥沙河流叶绿素a时空格局及其水体荧光特征OA

The main productivity of rivers comes from the energy conversion and material cycling of multi-trophic organisms in water ecosystems.This is very important for keeping water ecosystems in balance.The mass concentration of chlorophyll-a is an important indicator of primary productivity in water bodies.The mass concentration of chlorophyll-a is determined by the density of phytoplankton,and the yield of chlorophyll fluorescence is influenced by the photosynthetic activity of phytoplankton.Chlorophyll fluorescence has been extensively studied and used in aquatic ecological assessment as a probe for photosynthesis research.However,there is relatively limited research on the impact of the water environment on sediment-laden river characteristics in the Loess Plateau. This study established 27 sampling locations in the Beiluo River during the summer and fall of 2023 to collect surface water samples and provide insights into the state of primary productivity and its impact on chlorophyll-a fluorescence characteristics in a sediment-laden river on the Loess Plateau.Measurements were taken of the chlorophyll-a mass concentration and chlorophyll fluorescence parameters(fluorescence yield,absorption flux,trapping flux,electron transport flux,dissipated energy flux,etc.)of the water samples.Based on this,the spatiotemporal patterns of chlorophyll-a mass concentration in the Beiluo River were defined,and the relationship between chlorophyll-a mass concentration and the water body's fluorescence characteristics was determined. The findings demonstrated that phytoplankton photoinhibition was more severe in the fall than in the summer.A stable state was maintained by the positive correlation between the absorption,trapping,electron transport,and dissipated energy fluxes.chlorophyll-a mass concentration significantly affected the quantum yield of electron transport in the summer but had no discernible effect on chlorophyll fluorescence characteristics in the fall. There is spatial heterogeneity in the Beiluo River's chlorophyll-a mass concentration and chlorophyll fluorescence value.The lower reaches of the Beiluo River had a higher mass concentration of chlorophyll-a during the summer than the upper and middle reaches.The chlorophyll fluorescence value was higher in tributaries than in the middle reaches.The middle reaches had a higher mass concentration of chlorophyll-a in the fall than the lower reaches and tributaries.The tributaries had higher chlorophyll fluorescence values than the upstream.The phytoplankton in the Beiluo River can maintain a stable state of capturing and converting light energy in both summer and autumn to meet their energy requirements for growth and development.The amount of chlorophyll-a depends on phytoplankton density.Phytoplankton is closely related to water quality conditions.Therefore,future research needs to further reveal the cascade effect of water quality,phytoplankton,chlorophyll-a,and chlorophyll fluorescence characteristics in the Beiluo River,providing more comprehensive scientific support for the assessment and protection of water ecological quality in sediment-laden rivers.