What is a common consequence of untreated sewage being released into aquatic systems?

The release of untreated sewage into aquatic systems often leads to oxygen depletion, which is a significant environmental issue. When sewage enters a water body, it increases the nutrient levels, particularly nitrogen and phosphorus. This nutrient overload can cause excessive growth of algae in a process called eutrophication. As the algae eventually die off, their decomposition consumes a substantial amount of dissolved oxygen in the water, leading to hypoxic conditions or zones where oxygen levels are too low to support most aquatic life.

Oxygen depletion can have severe consequences for fish and other organisms that rely on dissolved oxygen to survive. In extreme cases, this can result in dead zones where aquatic life cannot be sustained, leading to a decline in fish populations and overall biodiversity in the affected water bodies. Therefore, the relationship between untreated sewage and oxygen depletion is crucial for understanding the impacts of pollution on aquatic ecosystems.