Dissolved oxygen in outdoor systems is produced by which processes?

• A. photosynthesis
• B. photosynthesis, wind/ wave action, aeration
• C. wave action
• D. aeration

Answer: (B)

Dissolved oxygen in outdoor systems comes from both biological production and physical transfer from the air. Photosynthesis by aquatic plants, macroalgae, and phytoplankton releases oxygen as these organisms convert light energy and carbon dioxide into sugars. Wind and wave action keep the surface agitated, boosting gas exchange at the air-water interface so more oxygen from the atmosphere dissolves into the water. Aeration directly adds oxygen by injecting air or oxygen-rich gas into the water, increasing the amount of oxygen that can dissolve. Daylight drives oxygen production through photosynthesis, while wind, waves, and aeration help replenish oxygen whenever it’s needed, including at night when photosynthesis drops.