California Wastewater Grade 3 Certification Practice Test – Practice Questions & Exam Prep

Nutrient overload in aquatic systems, often referred to as eutrophication, primarily leads to oxygen depletion and can cause significant harm to aquatic life. When an excess of nutrients, particularly nitrogen and phosphorus, enters the water, it promotes excessive growth of algae, known as algal blooms. As these algae die off, their decomposition consumes a substantial amount of dissolved oxygen in the water. This reduction in oxygen levels can create hypoxic (low-oxygen) or anoxic (no oxygen) conditions, which are detrimental to fish and other aquatic organisms.

In hypoxic conditions, fish and other aerobic organisms may struggle to survive due to insufficient oxygen for respiration. This can result in fish kills and a decline in overall biodiversity within the aquatic ecosystem. The impact of nutrient overload on oxygen levels is especially critical during warmer months when water temperatures are higher, and oxygen solubility decreases. Hence, the correct choice emphasizes the negative effects of nutrient overload, highlighting its potential to disrupt aquatic life through oxygen depletion.