The response of diatoms in sediment cores to environmental changes in the Changjiang River estuary over the past century

This study analyzed environmental changes in the Changjiang River Estuary over the past century through long-term observations of diatom communities in sediment cores. The increasing species richness and diversity of diatom assemblages in the core sediments since the 1930s, and shifts in dominant species, indicate that severe eutrophication has occurred in the Changjiang River estuary over the past several decades. Coscinodiscus argus and Coscinodiscus radiatus can serve as phytoplankton components for monitoring warm-water conditions, while Paralia sulcata acts as a key indicator of nutrient enrichment. Additionally, reduced sediment discharge has likely led to dissolved silicon (DSi) limitation and an imbalanced dissolved inorganic nitrogen to silicon (DIN:DSi) ratio, driving an ecological shift toward smaller species like, Pseudo-nitzschia pungens (10 μm) and Paralia sulcata (average 30 μm). Consequently, changes in diatom communities within sediment cores from the Changjiang River estuary and adjacent waters provide critical evidence for environmental evolution in this region.