A possible consequence of fertilizer runoff in aquatic ecosystems is eutrophication , which often leads to algal blooms that deplete oxygen and can kill fish and other aquatic life.

Quick Scoop

When rain washes excess fertilizer (rich in nitrogen and phosphorus) from farms or lawns into rivers, lakes, and coastal waters, those nutrients supercharge algae growth. As the thick algal blooms die and decompose, bacteria use up dissolved oxygen, creating low-oxygen or “dead zone” conditions where many fish and invertebrates cannot survive.

So, in one line for your question:

A likely consequence of fertilizer runoff in aquatic ecosystems is eutrophication, causing algal blooms and oxygen depletion that can lead to fish kills and loss of aquatic biodiversity.

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