The effects of water injection dredging on low-salinity estuarine ecosystems: Implications for fish and macroinvertebrate communities

Subaqueous dredging is a management activity undertaken globally to improve navigation, remove contaminants, mitigate flood risk and/or generate aggregate. Water Injection Dredging (WID) hydrodynamic technique involving the turbation and downstream displacement of fine sediments using vessel-mounted water jets. Despite being widely applied internationally, environmental ecological effects WID are poorly understood. For first time, this study used Before-After-Control-Impact (BACI) experimental design assess on physicochemistry, macroinvertebrate fish communities within 5.7 km-long reach tidal river. targeted central channel (thalweg) avoid disturbance margins banks. Mean but not peak turbidity levels were substantially elevated, dissolved oxygen reduced during periods WID, although relatively short-lived (?3 h average). resulted in significant reductions benthic community abundance (particularly taxa that burrow into sediments), taxonomic richness diversity. In contrast, minor changes detected marginal dredged following WID. Reductions diversity recorded most likely due behavioural avoidance sediment plume. No visibly stressed or dead sampled dredging. Results suggest mobile organisms largely unaffected by thalweg represents more ecologically sensitive alternative traditional margin mechanical techniques.