Answer:
Freezing
Step-by-step explanation:
During cold winter months, the water on the surface of lakes/water bodies changes its state from liquid to solid state (ice) and the process is known as freezing. This phenomenon helps the flora and fauna living under such water bodies survive even in extremely cold weather. The ice being less dense than water floats on the surface of lake and acts as a shield. This shield of ice acts as an insulator and restricts the outside cold waves from entering the water beneath the ice cover and maintains optimum temperature inside. Hence due to the change of state of water, the flora and fauna is able to survive even in harsh winter season.