Eutrophication of water bodies leading to killing of fishes is mainly due to non-availability of
Depletion of dissolved oxygen content in the water literally chokes the lake to death.
In cultural eutrophication, the prime contaminants are plant nutrients like nitrates and phosphates. They overstimulate the growth of algae, causing unsightly scum and unpleasant odours, and robbing the water of dissolved oxygen vital to other aquatic life.