Estuaries are most affected by human-induced nutrient loading, which leads to problems like algal blooms and hypoxia.

Estuaries are particularly sensitive to nutrient loading—the introduction of excess nutrients (often from fertilizers, sewage, or industrial runoff) into coastal waters. This can lead to eutrophication, where overgrowth of algae depletes oxygen levels in the water, creating "dead zones." This process significantly impacts biodiversity, fish populations, and overall ecosystem health. While coral reefs, wetlands, and mangrove forests can also be affected by nutrient loading, estuaries are most prone due to their proximity to urban and agricultural runoff.