Approximately 50% of oxygen comes from the ocean, where algae not only release oxygen during photosynthesis, but also serve as the base of most oceanic food webs. In this imagery, areas of the ocean with lower amounts of surface chlorophyll are colored blue, areas with higher concentrations are colored green to yellow. The large patches of gray are areas where the satellite cannot measure the ocean surface due to cloud cover. Read more here: https://sos.noaa.gov/Datasets/dataset.php?id=461 | NOA