Dredging and extraction of sand

Dredging is primarily performed to open up bays and to improve the accessibility of boats. But it is also performed to restore aquatic environments, which benefit fish and other aquatic organisms by opening up overgrown river and streams for migrating fish, or removing sediment with high levels of toxins or nutrients.

Picture: Dredging

Where dredging takes place organisms are initially completely wiped out and may at worst never re-colonize the affected area. The dredged sediments also have negative effects on the location where they are dumped, since they may cover the sea floor and its organism. Further, dredge spoils may contain toxins and chemicals which are dislodged in the process and injected into the water column. The location of the dumping of dredge spills is therefore very important.

Sand and gravel extracted from the sea floor is used as material for building roads, making glass and so on. The extraction may have negative effects on bottom-dwelling organisms, and also cause erosion.

Sources

Lundberg, C. et al (2012). Undervattensmiljö i Norra Östersjön – Viktigt att tänka på vid havsnära planering. Närings-, trafik- och miljöcentralen, Helsingfors.