Each winter, ice covers a lake. during this time, fish in the lake have a smaller food supply. what kind of disturbance is this?

This kind of a disturbance is the  Cylical  disturbance. During winter, ice covers a lake, however the fish wont freeze but will have  smaller food supply; this is because the fish go further down than the ice, the ice usually does not freeze all the way to the bottom, but remains at the surface since it is less denser than the liquid water. 

We can plant more trees and plants.