Answer:
Eutrophication: An abundance of cyanobacteria (an algal bloom) is caused by an excess amount of nutrients in the water (phosphorus and/or nitrogen) which depletes the water of oxygen which is vital for plant an animal life. Oxygen is crucial for the survival of an organism, so when there is a lack of oxygen, the results can be fatal. That is why when there are reports of algal blooms, there are almost always mentions of an abundance of dead fish, birds, and other water dwelling organisms (these organisms live in the water, drink from it or use it as breeding grounds etc,) Not only that, but algal blooms produce toxins that can make animals and humans fall ill.
Dead zones: As stated previously, harmful algal blooms deprive the water of oxygen.This can lead to the extreme and create dead zones. Dead zones are zones in an aquatic body where the oxygen levels are not sufficient enough to support aquatic life. Hence why there is no life in dead zones because all of the fish either die, or leave.
Both affect the population of native species and the overall wellbeing of the bodies of water.
Step-by-step explanation:
put above answer line for anyone who can only see preview :)