Seasonal patterns and phytoplankton blooms influence sediment FA composition in a large reservoir

This study investigated the spatial and temporal dynamics of sediment fatty acid composition in the backwater areas of two tributaries of the Three Gorges Reservoir, examining its relationships with both phytoplankton communities and water quality. Sediment FA composition was used as an indicator of microbial community structure and organic matter sources, while stable isotope analysis was used to determined whether sediment carbon was primarily autochthonous or allochthonous.

Sampling was conducted at six sites in 2021—three in the Pengxi River and three in the Modao River, including locations with a history of phytoplankton blooms. Samples collected included sediment fatty acid composition, stable isotopes, pelagic phytoplankton communities, and water quality variables. Sampling took place during winter (March), spring (May), and summer (September) to capture seasonal and operational variations in the Three Gorges Reservoir, with additional daily sampling during the bloom period to assess fine-scale variability. In addition, daily sediment stable isotope samples were collected during spring 2022.