The Brainliest Answer!
In specific words , 
growth of algae leads to EUTROPHICATION .
which leads to unavability  of nutrients in water and it prevents sunlight to reach the plants at the bottom as the algae formation laeds to the formation of layer above the water.
HOPE IT HELP!!!!!!!!!
4 4 4
It covers the whole water hiding it from air, sun light this cause deficiency of oxygen and animals living in that water body are died
2 4 2