What issue is commonly caused by excess nutrients in water?

The issue commonly caused by excess nutrients in water is decreased fish populations. When there are high levels of nutrients, particularly nitrogen and phosphorus, it can lead to a phenomenon known as eutrophication. This process increases the growth of algae blooms, which can deplete oxygen levels in the water as they die and decompose. The resulting low oxygen conditions, or hypoxia, can create a hostile environment for aquatic life, resulting in decreased fish populations and other aquatic organisms.

The relationship between nutrient overload and aquatic health is crucial. Healthy fish populations rely on balanced nutrient levels to ensure proper growth, reproduction, and survival. When nutrient levels are excess, it disrupts the ecosystem balance, leading not only to reduced fish populations but also to broader ecological consequences.