What effect can large amounts of decomposing plants have on dissolved oxygen levels in water?

Large amounts of decomposing plants can significantly lower the dissolved oxygen levels in water. This process occurs because as plants decompose, microorganisms break down the organic material. This decomposition process consumes oxygen from the water, leading to a decrease in dissolved oxygen levels.

Dissolved oxygen is essential for aquatic life, as fish and other organisms rely on it for respiration. When large quantities of plant matter decompose, the increased microbial activity can lead to a rapid depletion of available oxygen, potentially resulting in hypoxic conditions (low oxygen levels) that can harm or even kill fish and other aquatic organisms.

This phenomenon is particularly noticeable in bodies of water that experience eutrophication, where nutrient overload promotes excessive plant growth. The subsequent decay of these plants can create a cycle of oxygen depletion and can adversely affect the overall health of the aquatic ecosystem.