The process in which diurnal oxygen shifts can occur in a river after organic matter is added is called ______.

Question

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Self-purification is the process in which a river can naturally cleanse itself of pollutants through various physical, chemical, and biological processes. When organic matter is added to a river, it can lead to an increase in oxygen demand by microorganisms that decompose the organic matter. This can cause diurnal oxygen shifts, where oxygen levels are lower at night when photosynthesis by aquatic plants ceases and respiration by microbes continues. However, during the day, oxygen levels can increase as photosynthesis by plants produces oxygen. Overall, self-purification can help maintain the health of a river ecosystem.

The Process in Which Diurnal Oxygen Shifts Can Occur in a River