Which process by phytoplankton contributes to global oxygen production and carbon cycling?

Which process by phytoplankton contributes to global oxygen production and carbon cycling?

• A. Cellular respiration
• B. Chemosynthesis
• C. Fermentation
• D. Photosynthesis

Answer: (D)

Photosynthesis. Phytoplankton capture light energy to convert carbon dioxide and water into organic matter, releasing oxygen in the process. This makes them a major source of global oxygen and a key driver of carbon cycling in the oceans. The produced organic matter becomes the base of the marine food web, and some of the carbon is stored when organisms die or produce sediments, helping sequester carbon in deep waters. In contrast, cellular respiration uses oxygen to release energy and consumes oxygen; fermentation can occur without light and does not produce oxygen; chemosynthesis uses chemical energy rather than sunlight and is not the typical process carried out by phytoplankton.