Question

question 3
what causes eutrophication of a body of water?
○ an increase in the nutrients available to the primary producers.
○ the build-up of toxins in the system over time.
○ a significant decrease in the amount of sunlight reaching the bottom.
○ the introduction of a non-native species of plant or animal.

Explanation:

Eutrophication is driven by excess nutrients (like nitrogen and phosphorus) entering water bodies. These nutrients fuel rapid growth of primary producers (algae, aquatic plants), leading to oxygen depletion and ecosystem disruption. The other options describe different aquatic issues: toxin buildup is bioaccumulation, reduced sunlight is light limitation, and non-native species cause biological invasion.

Answer:

An increase in the nutrients available to the primary producers.