Which gas is released by marine organisms and contributes to ocean oxygen levels?

Marine organisms, particularly phytoplankton, perform photosynthesis, a process in which they utilize sunlight, carbon dioxide, and water to produce glucose and release oxygen as a byproduct. This oxygen is crucial for both marine life and the atmosphere; it contributes significantly to the overall oxygen levels in the ocean. As these organisms spread throughout the sunlit layers of the ocean, they become vital players in the carbon cycle, helping to regulate carbon dioxide levels while simultaneously enriching the ocean with oxygen. Thus, the release of oxygen by marine organisms directly supports the respiration needs of many aquatic creatures and plays a key role in maintaining the health of ocean ecosystems.