Question

phosphate and nitrogen from fertilizers have entered a lake, causing eutrophication. as a result, algae populations grow rapidly, forming thick layers on the surface of the water. these algae block sunlight from reaching underwater plants, and when the algae die and decompose, the amount of dissolved oxygen in the water decreases. which of the following outcomes is most likely to occur in this lake? a phosphate levels in the lake decrease. b fish populations in the lake decline. c plant populations in the lake increase. d plant populations in the lake remain unchanged.

Explanation:

When algae block sunlight from underwater plants, the plants' photosynthesis is affected and their populations may decline. When algae die and decompose, dissolved - oxygen levels decrease. Fish need dissolved oxygen to survive. So, a decrease in dissolved oxygen will likely cause fish populations to decline. Phosphate levels initially increase due to fertilizer runoff and won't decrease without external processes to remove them.

Answer:

B. Fish populations in the lake decline.