What primarily causes low dissolved oxygen levels in swamp water?

Low dissolved oxygen levels in swamp water are primarily caused by the rapid consumption of oxygen by decomposing organic matter. In swamp environments, where organic material like dead plants and animals accumulates, the decomposition process is often facilitated by bacteria and other microorganisms. This process consumes large amounts of dissolved oxygen, especially when there is a significant amount of organic matter present. When the decomposition rate exceeds the rate at which oxygen is replenished, it leads to a decrease in dissolved oxygen levels, creating conditions that can be detrimental to aquatic life.

Although high water temperatures can impact gas solubility, excessive phytoplankton blooms can lead to oxygen depletion during nighttime respiration, and high sediment levels can affect light penetration and habitat quality, the most direct and immediate cause of low dissolved oxygen in swamps is the breakdown and decay of organic materials, which draws down the available oxygen in the water.