While marine life is inevitably affected by dredging, research and ongoing monitoring studies have demonstrated that the principal impacts of physical disturbance and removal are confined to the actual dredging area.
These impacts are generally short-lived and so long as the extraction operations are carefully sighted and managed, represent no long-term threat to biodiversity.
After dredging is completed, operators are required to leave the seabed a similar condition to that which existed prior to dredging commencing. Re-colonisation begins almost immediately and typically the seabed is biologically similar within two to ten years, depending on the seabed sediment type and the physical processes (waves, tides and sediment transport) it is naturally exposed to.
Sediment plumes arising from screening operations may also potentially affect life in surrounding areas. However, away from the immediate vicinity of the dredging vessel (>500m), the suspended sediments are present in such low concentrations that they have no discernable effect on biological communities that are already well adapted to live in such conditions naturally.
You can get an expert view on the impact of dredging on marine life by watching a specially commissioned BMAPA video.