It freezes on the surface of the water, and the density of the water is highest at about four degrees, so the water under the ice can slowly accumulate nutrients
Icing on the surface of the water, the density of the water is highest at about four degrees, so the water under the ice can slowly stock up nutrients.
When the surface of water freezes, the density of water is the highest at about four degrees, so the water under the ice can slowly accumulate nutrients