Section: Natural Sciences

3) Eutrophication of a lake may occur

1. when essential nutrients are insufficient.
2. as a result of too many fish.
3. during prolonged high temperatures.
4. when there is insufficient phosphorus.
5. when there is excess phosphorus.
6. No Answer Selected

Eutrophication occurs when chemical fertilizers containing phosphorus and nitrogen wash into a lake causing photoplankton and bottom vegetation to reach high productivity. This tremendous growth blocks out light, causing deeper plants to die while certain decomposers use all the oxygen, thus suffocating the fish.