Spatio-temporal evolution of wetland landscape and their ecological effects in the Liaohe Estuary, China

Estuarine wetlands support biodiversity, regulate land-sea material fluxes, provide ecosystem services, and buffer the effects of sea-level rise. However, rapid anthropogenic disturbances over the past decade have significantly altered the natural landscape of estuarine wetlands, threatening the living of ecosystem. In this study, we used Landsat images from 2015, 2021, and 2024 to quantify the landscape changes in the Liaohe Estuary wetland, China. Meanwhile, 22 surface sediments were collected in this estuary in 2021 and measured for concentrations of heavy metals to characterize their spatial distributions, potential sources, and ecological risks. Results revealed that the concentrations of Pb, As, Cr, Cu, Zn, and Cd were lower than values reported in 2014, whereas Ba, Pb, Hg, Zn, and Cd exceeded their corresponding local soil background values. Compared with other global wetland systems such as the Yellow River Delta, the overall heavy metal levels in the study area were relatively lower, except for Ni and Cd. Principal component analysis indicated that Cu, Zn, Pb, Hg, As, and Cd were mainly sourced from anthropogenic activities, including industrial wastewater discharge and aquaculture. Because sediment chemistry was measured only in 2021 and no statistical association with landscape metrics was detected, spatial co-occurrence with artificial landscapes is interpreted as hypothesis-generating rather than causal evidence. The integrated potential ecological risk index classified 23% of stations as low risk, 50% as moderate risk, and 27% as high risk, with Hg and Cd dominating the risk. These findings provide a baseline for targeted monitoring and wetland management.