Phytoplankton: The Invisible Forest
Recent news reports regarding the ongoing fires in the Amazon Rain Forest have been a bit inaccurate about the oxygen generated by this wondrous landscape. The title “lungs of the Earth”—is a gross overestimate. As several scientists have pointed out
recently, the Amazon’s net contribution to the oxygen we breathe likely hovers around zero.
Plants also use
oxygen during times of lowered oxygen availability (like during nighttime), and decomposing plant matter also uses oxygen. “Because of this balance between oxygen production and consumption, modern ecosystems barely budge oxygen levels in the atmosphere. Instead, the oxygen we breathe is the legacy of phytoplankton in the ocean that have over billions of years steadily accumulated oxygen that made the atmosphere breathable”, explains Scott Denning
, at atmospheric scientist at Colorado State University.
A sea water filled soda can holds 75-100 million phytoplankton. Phytoplankton are microscopic algae that live wherever sunlight shines on water, creating their own food via photosynthesis. Over 50% of the oxygen we breath is made by this Invisible Forest, which also removes CO2 added by human activities from the oceans & atmosphere…effectively maintaining the CO2/O2 balance for the past 550 million years.
Phytoplankton use carbon, water, and nutrients in sea water to live and grow. Nutrient-rich waters rise, from the cold ocean’s depths to the surface in an ongoing cycle called “The Biological Pump”, or Ocean Inversion, an upwelling of water caused by differences in water densities, temperatures, and currents. As plankton blooms deplete the nutrients and die, their remains sink to the ocean floor and, through inversion, resurface as nutrients to feed other plankton…much like tilled-in plants feed the soil in our gardens.
This plankton-nutrient-plankton cycle takes about 1600 years. Some of the dead plankton form layers of carbon-rich matter on the sea floor acting as the Earth’s carbon sink…effectively holding carbon as a soil-turned-to-rock layer for 100’s of millions of years. The White Cliffs of Dover were thus formed by calcium-rich plankton. Chemicals released by decaying phytoplankton give the sea-shore area it’s familiar “sea air” scent.
Global warming is increasing precipitation rates and melting sea ice, adding fresh water to the ocean. This reduces sea water density, effectively capping the seas with a light layer of water causing the Ocean Inversion action to slow. The cycling of nutrient-rich waters from the depths to feed phytoplankton are slowed and their populations suffer. Oxygen manufacturing by phytoplankton is thus slowed, CO2 cycling is reduced, and the health of our atmosphere is disrupted.
This elevated level of CO2 causes a wetter, warmer atmosphere…increasing the occurrences and strengths of storms, adding yet more fresh water to the ocean, further depleting phytoplankton populations…
By the way, over 50% of Earth’s oxygen comes from phytoplankton.