Final answer:
Water molecules form a distinct structure when they freeze, causing ice to have a lower density than liquid water. This unique property allows ice to float on water. In a frozen lake, ice serves as an insulating barrier, protecting fish and other organisms from freezing in the water.
Step-by-step explanation:
In the liquid state, the hydrogen bonds of water can break and reform as the molecules flow from one place to another. When water is cooled, the molecules begin to slow down. Eventually, when water is frozen to ice, the hydrogen bonds become more rigid and form a well-defined network. The bent shape of the molecules leads to gaps in the hydrogen bonding network of ice. Ice has the very unusual property that its solid state is less dense than its liquid state. As a result, ice floats in liquid water.
Ice's impact on a population of rainbow trout fish, Oncorhynchus mykiss, in a frozen lake in winter is significant. The layer of ice that forms on the surface of the lake creates an insulating barrier, protecting the fish and other organisms living beneath from freezing in the water. Without this layer of ice, the fish would freeze and be unable to move freely, making survival in cold temperatures difficult or impossible.