What impact does agricultural runoff have on water bodies?

Agricultural runoff has a significant impact on water bodies primarily because it introduces fertilizers and pesticides, which lead to nutrient pollution. When rain or irrigation water flows over agricultural fields, it can carry excess nutrients such as nitrogen and phosphorus from fertilizers into nearby rivers, lakes, and streams. This influx of nutrients can cause a process known as eutrophication, where excessive nutrients fuel the growth of algae blooms. These algae can deplete oxygen levels in the water, harm aquatic life, and disrupt ecosystems.

In contrast, the other options do not accurately reflect the impact of agricultural runoff. For instance, agricultural runoff does not typically reduce water levels; rather, it affects water quality. It also does not create habitats for aquatic wildlife as the introduction of pollutants can degrade those habitats instead. Additionally, agricultural runoff is not involved in the removal of harmful substances from water; rather, it contributes to pollution, which can harm aquatic ecosystems. Thus, the choice regarding the introduction of fertilizers and pesticides leading to nutrient pollution correctly identifies the detrimental effects of agricultural runoff on water bodies.