The ocean plays a crucial role in producing oxygen through a process called photosynthesis performed by marine plants, primarily phytoplankton. However, it is important to note that the exact percentage of oxygen produced by the ocean is challenging to determine accurately.
Estimates suggest that marine plants, including phytoplankton, contribute approximately 50-85% of the oxygen in Earth's atmosphere. Phytoplankton are microscopic marine plants that carry out photosynthesis using sunlight, carbon dioxide, and nutrients dissolved in the water. They are responsible for about half of the global primary production of organic matter, making them significant contributors to oxygen production.
Additionally, other marine organisms, such as seaweeds (macroalgae) and marine plants in coastal ecosystems like seagrasses and mangroves, also contribute to oxygen production. These habitats contribute to the overall oxygen production by the ocean.
While the ocean is a vital oxygen producer, it's important to note that terrestrial plants, including trees and forests, contribute a significant portion of the Earth's oxygen as well. The exact balance between oxygen production by the ocean and terrestrial ecosystems is complex and interconnected, making it challenging to assign precise percentages.