What condition is commonly caused by increased oxygen demand in lakes and streams due to organic enrichment?

The correct answer is oxygen depletion, as this condition arises when there is an increased demand for oxygen in aquatic environments, such as lakes and streams, primarily due to organic enrichment. When organic materials, like plant debris and wastewater, enter these water bodies, they become a food source for microorganisms. These microorganisms break down the organic matter, a process that requires oxygen.

As the decomposition activity increases, the available dissolved oxygen levels in the water reduce, which can lead to hypoxic or anoxic conditions, adversely impacting fish and other aquatic organisms that depend on adequate oxygen levels for survival. Therefore, the phenomenon of decreased oxygen levels or oxygen depletion directly correlates with heightened organic enrichment in the water body.

Understanding this process is crucial for managing water quality, especially in industrial and urban areas where runoff can carry organic materials into nearby lakes and streams, significantly affecting their ecological balance.