Which conclusion about the environmental impact of farming is supported by observing fertilizer run-off?

Observing fertilizer run-off supports the conclusion that it can cause algal blooms due to the excess nutrients, particularly nitrogen and phosphorus, that enter water bodies. When fertilizers are applied to crops and then washed away by rain or irrigation, they can flow into nearby lakes, rivers, or oceans.

The introduction of these nutrients into aquatic ecosystems can stimulate rapid growth of algae, leading to a phenomenon known as algal blooms. Algal blooms can deplete oxygen in the water, leading to dead zones where marine life cannot survive, and they can also produce toxins that affect both aquatic animals and humans. Thus, the observation of fertilizer run-off directly correlates with the potential for these harmful algal blooms, making this conclusion supported by evidence in real-world environmental science.