Why does ice float on water? how does this affect life in earth’s aquatic environments?

This because ice is less dense than water of particular temperature range.  Water reaches its maximum density at 4 degrees. Ice is important especially for aquatic  life in the polar regions. Polar bears give birth and hunt on sea ice and they need it to travel from one region to another. The ice edge in coastal areas is an important feeding ground for the walrus that uses the ice as diving platforms to feed on clams on the sea floor. Ice algae grow at the porous bottom of sea ice and form the base of the unique marine food web connected to sea ice