This is what happens when bodies of water, like lakes, estuaries, or slow-moving streams, receive excess nutrients that promote excessive plant growth. This plant growth reduces dissolved oxygen in the water when dead plant material decomposes and causes the death of other organisms present:

eutrophication

Explanation: eutrophication occurs when chemicals like fertilizers are washed into water bodies and excess algae growth occurs. This excess growth occurs due to plenty of nutrients in the water. Such algae when they eventually die can cause oxygen depletion in water bodies thereby affect the ability of other organisms found in the water,to breath. This may lead to death of fishes and other aquatic lives. Causing the water to have bad odour and taste.

Algae growth may also prevent sunlight from reaching plants that are at the bottom of the water bodies,as a result affecting the aquatic food chain