Emerging environmental risks to the largest coastal lagoon (Pinqing Lagoon) on the Chinese mainland: Assessment through a water-sediment-ecological perspective.

Abstract

Coastal lagoons are vital yet vulnerable marine ecosystems. This study analyzes a five-year dataset to evaluate changes in water quality and their impacts on biota in Pinqing Lagoon (PQL). Seasonal surveys conducted from 2019 to 2023 across 14 sites revealed significant variability in water and sediment quality parameters. During the wet summer season, water quality deteriorated significantly as nutrient levels peaked. In contrast, the dry winter season posed a high ecological risk from heavy metals (HMs), specifically Cu, Hg, and Cd, in sediments. Sediment core analysis indicates upward trends in HMs since the 1950s. Salinity and pH are the primary drivers shaping the benthic communities in transitional zones, while nutrients and HMs primarily affect organisms in the inner bay. Nutrient enrichment has exacerbated HM accumulation and ecological degradation, with tolerance to HMs emerging as a critical factor for benthic survival. This comprehensive assessment of PQL highlights the seasonal patterns of pollution in urban lagoons, providing valuable insights for future conservation efforts.