Global meta-analysis deciphering ecological restoration performance of dredging: Divergent variabilities of pollutants and hydrobiontes.

Global "Sustainable Development Goals" propose ambitious targets to protect water resource and provide clean water, whereas comprehensive understanding of restoration performance and ecological mechanisms are lacking for dredging adopted for purifying polluted waterbodies and maintaining navigation channels. Here, we conducted a global meta-analysis to estimate ecological restoration consequence of dredging as pollution mitigation and navigation channel maintenance measures using a dataset compiled from 191 articles covering 696 studies and 84 environmental and ecological parameters (e.g., pollutants and hydrobiontes). We confirm that dredging shows negative influences on 77.50% pollutants in the BA model (before dredging vs. after dredging) and 84.21% pollutants in the CI model (control vs. impact) as well as on sediment nutrient fluxes. Additionally, 57.14% attributes (i.e., richness, diversity, biomass, and density) of hydrobiontes in the BA model and 89.47% attributes of hydrobiontes in the CI model responded negatively to dredging. As a result, 76.32% of the pollutants and 61.11% of the hydrobiont attributes responded uniformly to dredging in the BA and CI models. Our findings emphasize that dredging generally decreases pollutants and mitigates algal blooms, controlling phosphorus is easier than controlling nitrogen by dredging, and attributes (i.e., richness, diversity, and biomass) of hydrobiontes (i.e., zooplankton, phytoplankton, and zoobenthos) are density-dependent in dredging-disturbed environments. Our findings broaden our knowledge on ecological restoration performance of dredging as a mitigation measure in global aquatic ecosystems, and these findings might be helpful to use and optimize dredging to efficiently and sustainably purify polluted aquatic ecosystems.