Correlation between phytoplankton dynamics and hydrometeorological factors in the Three Gorges reservoir area tributary

ABSTRACT Phytoplankton blooms in reservoir areas’ rivers are a research problem of wide interest. To assess the influence of hydrometeorological factors on the occurrence and development of phytoplankton blooms in the Xiangxi River, a major tributary of the Three Gorges Reservoir. We employed the generalized additive model (GAM) and Random Forest importance analysis to evaluate the impact of hydrometeorological factors on phytoplankton dynamics. The findings revealed that river flow in the Xiangxi River is the most crucial factor affecting phytoplankton, with a significant decrease in phytoplankton observed when the flow exceeds 100 m3/s. At the Xiakou station within the perennial backwater area, phytoplankton exhibited correlations with river flow, temperature, solar radiation, and wind speed, with decreasing levels of importance. At the Pingyikou station and the Zhaojun station within the dynamic backwater area, phytoplankton was correlated with river flow, solar radiation, and precipitation. Furthermore, an increase in wind speed at the Xiakou station was significantly positively correlated with an increase in phytoplankton, suggesting that wind speed plays a promoting role in phytoplankton aggregation in the perennial backwater area. These results underscore the significance of hydrometeorological factors as key determinants in assessing the occurrence and development of phytoplankton blooms. This research provides valuable insights for phytoplankton blooms prediction and warning systems.