Question

agricultural runoff can carry fertilizers into lakes and streams. this runoff can cause algae populations to greatly increase. which effect does this change in the algae population sizes most likely have on affected lakes and streams? a reduction in water clarity, a reduction in dissolved oxygen needed by fish and shellfish, a reduction in temperature variations near the waters surface, an increase in water level

Explanation:

When algae populations grow rapidly due to nutrient - rich runoff, they eventually die and decompose. The decomposition process consumes dissolved oxygen in the water, which can lead to a reduction in the dissolved oxygen available for fish and shellfish.

Answer:

a reduction in dissolved oxygen needed by fish and shellfish