Final answer:
When too much fertilizer is added to soil, it can lead to nutrient pollution in waterways, causing algal overgrowth and harming aquatic organisms.
Step-by-step explanation:
When people add too much fertilizer to soil, it can lead to nutrient pollution in waterways through runoff. Excess nitrogen and phosphorus from the fertilizers can cause the overgrowth of algae in bodies of water, a process known as eutrophication.
This overgrowth can clog waterways, reduce sunlight penetration, deplete oxygen levels, and ultimately harm aquatic organisms like fish and shellfish. Additionally, some algal blooms can produce toxins that pose a health risk to humans when they consume contaminated fish or shellfish.