How does a surface layer of ice help aquatic life survive winter?

Because ice is less dense than liquid water, it forms a layer on the surface of lakes and rivers rather than sinking to the bottom. This surface ice acts as an essential insulating cover that protects aquatic life during the winter.1234

By creating a barrier between the cold air above and the water below, the ice layer prevents the entire water column from freezing solid. This insulation helps regulate the temperature of the water beneath, allowing it to remain in a liquid state where many aquatic organisms can survive the cold season. While surface temperatures may reach the freezing point, the water deeper down often remains warmer, providing a necessary refuge for fish and other ectotherms that rely on the surrounding environment to regulate their body temperature.5216