What causes oxygen depletion when organic wastes are discharged into water?

When organic wastes are discharged into water, the primary cause of oxygen depletion is the consumption of oxygen by bacteria as they decompose the organic material. Bacteria are microorganisms that thrive in nutrient-rich environments, such as those created by organic waste. As these bacteria metabolize the organic matter, they require oxygen in the process of respiration, which leads to a reduction in the dissolved oxygen levels in the water.

This oxygen depletion can create a critical situation for aquatic life, as many aquatic organisms, such as fish and invertebrates, rely on dissolved oxygen to survive. If the oxygen levels drop too low, it can lead to hypoxic conditions, depriving these organisms of the essential oxygen they need to thrive.

In contrast, while higher temperatures can indeed influence oxygen levels and reduce solubility, they are not the primary mechanism by which organic waste leads to oxygen depletion. Reduced water flow can impact oxygen saturation; however, it is not the direct cause in the context of organic matter breakdown. Similarly, while chemical reactions can consume oxygen, the phenomenon related to organic waste specifically relates most directly to biological consumption by bacteria.