At what depth would you expect to see the highest concentration of oxygen (O2)?

• A. 0 cm
• B. 10 cm
• C. 15 cm
• D. 20 cm

Answer: (A)

The highest concentration of oxygen (O2) in a body of water is typically found at the surface layer, which is influenced by several factors. This is where photosynthesis occurs most effectively due to the availability of sunlight, allowing aquatic plants and phytoplankton to produce oxygen. The mixing of water due to wind action and wave movements also contributes to higher oxygen levels at the surface because it facilitates the exchange of gases between the atmosphere and water.

As depth increases, factors such as reduced light penetration and decreased rates of photosynthesis result in lower concentrations of oxygen. Additionally, the decomposition of organic material at greater depths can consume oxygen, further lowering its levels. Therefore, it is expected that the concentration of oxygen would be highest at a depth of 0 cm, which represents the surface of the water.