Marine organisms produce over half of the oxygen that land animals need to breathe.
Humans and almost all other animals depend on oxygen in the atmosphere or water to respire—that is, to produce energy at the cellular level necessary for survival. Most sea animals extract oxygen directly from ocean water, while land animals breathe air from Earth’s atmosphere, which consists of about 21 percent pure oxygen.
Oxygen has not always been a given element in the air; in fact, its presence is a relatively recent development in Earth’s history. Until around 600 million years ago, our atmosphere was composed of less than five percent oxygen, instead being mainly a nitrogen and carbon dioxide mixture dating back to Earth’s formative volcanic activity over four billion years ago.
Fortunately for us, organisms evolved that could use carbon dioxide, along with solar radiation, to produce metabolic energy and oxygen—a process called photosynthesis. Whlie we may think of photosynthesis as the life process of land plants, algae and a variety of other microscopic organisms called phytoplankton had been using photosynthesis long before terrestrial plants appeared…
(read more: NOAA Ocean Explorer)
Image courtesy of the NOAA MESA Project