Interactions of multiple abiotic stresses exacerbate mollusk diversity loss in a high-discharge coastal mangrove wetland

Coastal regions, as a hotspot region of biodiversity and the most densely populated areas in the world, are increasingly threatened by anthropogenic disturbances, including warming, acidification, eutrophication, salinity fluctuation, and oxygen loss. Although massive single-factor studies have revealed the ecological catastrophe caused by these impacts, how these impact stressors interact to endanger coastal biodiversity that is critical for ecosystem stability and human well-being is still poorly understood. To investigate whether and how water warming, acidification, eutrophication, salinity fluctuation and oxygen loss interact with each other to impact the mangrove mollusk diversity, a long-term study was conducted in the mangroves of Chinese Daya Bay from 1987-1993 to 2017-2021. We found that water temperature, chlorophyll-a, total nitrogen (TN) and total phosphorus (TP) increased significantly, while the water pH, salinity, dissolved oxygen (DO) and mollusk species richness decreased obviously, reflecting water warming, eutrophication, acidification, salinity fluctuation, oxygen loss and biodiversity loss occurred in the Daya Bay. The mangrove mollusk diversity had a significant response to the water warming, eutrophication, acidification, salinity fluctuation, oxygen loss (p < 0.001). The average incidences of mollusk diversity loss due to the changes in water pH, temperature, TP, TN, chlorophyll-a, salinity and DO were 47.11 %, 35.56 %, 35.53 %, 34.48 %, 34.22 %, 34.15 % and 33.05 %, respectively. Moreover, the average effect of interactions between any two water factors on the mollusk diversity was 0.998, which was 22.5 % larger than their single effect on biodiversity of 0.814. The findings suggest that interactions between global change stressors can exacerbate biodiversity loss in coastal wetlands. Quantifying those effects in terms of multi-factor interactions will contribute to the coastal management and restoration based upon combined evidence rather than a one-sided single perspective.