Which of these can decrease due to fertilizer in waterways? oxygen, nitrogen, bacteria, algae

The correct answer is oxygen.

The agricultural runoff result in carrying away the fertilisers in the water bodies. The nutrients present in the fertilizers allow the blooming of the algae, the extensive growth of algae block the water ways. Due to presence of large colonies of algae, a large number of algae die. The dead algae sink into bottom and decompose, which removes the oxygen from the water.

the answer to your question is a plant

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