Page 37 - living-ice

Sea ice in shallow waters
In shallow and coastal waters, sea ice has a direct physical effect on benthic (or bottom-dwelling) organisms because ice oes and ice ridges gouge and scour the seabed. This activity disturbs both the soft seabed and benthic communities in- habiting it. A seabed that is scraped has fewer organisms and species than other parts of the seabed. Only mobile or opportunistic organisms move into these areas in the summer when the coastal ice has melted. Examples of such mobile and opp- ortunistic organisms include scavengers such as isopods, predators such as certain sand hoppers and rapidly growing bristle worms.
In areas with glaciers and icebergs, gouging by sea ice can affect the seabed down to more than 100 meters water depth, but in shallow waters scouring is most common. Shallow coastal waters with a tidal zone usually have a distinct zonation with distinctive animals and macroalgae, but in the Arctic scouring removes this zonal distribution.
On the one hand the ice disrupts the seabed and benthic communities as described above, while on the other hand sea ice forms a “lid” that prevents ships from entering ice-covered waters. When areas of the continental shelf become ice-free, trawlers may take over the scraping of the seabed in their search for cod and shrimps.
Sidescan sonar mosaic of ice scours offshore of southern Cornwall Island, Canada, 1992 IMAGE: Steve Blasco, Geological Survey of Canada