How is O2 added to aerobic ponds?

• A. Oxygen diffusion
• B. Heat transfer from solar radiation
• C. Algae, or mechanical aeration
• D. Diffusion from groundwater

Answer: (C)

Oxygen is added to aerobic ponds mainly through two mechanisms: the algae in the pond produce oxygen during photosynthesis when there is light, and mechanical aeration devices physically bubble air into the water, increasing gas exchange and dissolving more oxygen. Algae release O2 as a byproduct of photosynthesis, so DO tends to rise during the day. Mechanical aeration, using aerators or diffusers, continually supplies oxygen by increasing contact with air, which is especially important when there isn’t enough light for photosynthesis or when DO drops. Oxygen entering by diffusion from the air is possible but generally slower and not relied on as the primary source, and heat from solar radiation affects DO by changing water temperature (warmer water holds less dissolved oxygen) rather than actively adding oxygen. Groundwater diffusion contributes negligible DO to the pond.