Plant populations in the lake increase. More predatory birds feed on lake animals. Phosphate levels in the lake decrease. Fish populations in the lake decline.
I gave my students this multiple choice question: An increase in phosphate levels in a lake increases the population of algae in the lake. Increased algae blocks sunlight into the lake and results in a decrease in dissolved oxygen in the lake's water. Which of the following should be expected as a result?

Only one answer is correct among these 4 choices:
- Plant populations in the lake increase.
- More predatory birds feed on lake animals.
- Phosphate levels in the lake decrease.
- Fish populations in the lake decline.

Could you tell me which one is correct?

Fish populations in the lake decline.