Question

when water pollution reduces the amount of sunlight in an aquatic ecosystem, which of these happens?
fish grow larger and larger indefinitely.
turbidity (cloudiness) increases leading to less plant growth.
dissolved oxygen completely disappears and is replaced with helium.
more sunlight causes more plants to grow along the bottom.

Explanation:

Water pollution often increases turbidity (cloudiness) in aquatic ecosystems. This reduces the amount of sunlight that can penetrate the water. Aquatic plants need sunlight for photosynthesis. With less sunlight due to increased turbidity, plant growth is reduced. Fish do not grow indefinitely as they have biological limits. Dissolved oxygen does not disappear and get replaced by helium. And if sunlight is reduced (not increased as in the last option), it cannot cause more plants to grow.

Answer:

Turbidity (cloudiness) INCREASES leading to less plant growth.