It is amazing how some of the smallest things on Earth are very important. Phytoplankton capture CO2 in the ocean and use the carbon to produce mass and release the oxygen. Wikipedia says between 50% to 80 % of our atmospheric oxygen is produced by the phytoplankton. Other reference use about 50%. Phytoplankton have chlorophyll to capture sunlight, and they use photosynthesis to turn it into chemical energy. Really no difference from that of terrestrial plants.
EarthobservatoryNASA, gov describes phytoplankton as follows:
Derived from the Greek words phyto (plant) and plankton (made to wander or drift), phytoplankton are microscopic organisms that live in watery environments, both salty and fresh.
Some phytoplankton are bacteria, some are protists*, and most are single-celled plants. Among the common kinds are cyanobacteria, silica-encased diatoms, dinoflagellates, green algae, and chalk-coated coccolithophores.
*Protists are not animal, nor plant nor fungus. An Amoeba is classified as a protist, for example.
Equally as important to the replenishing of the oxygen is the following:
“Phytoplankton are the foundation of the aquatic food web, the primary producers, feeding everything from microscopic, animal-like zooplankton to multi-ton whales. Small fish and invertebrates also graze on the plant-like organisms, and then those smaller animals are eaten by bigger ones.”
Phytoplankton can also be the harbingers of death or disease. Certain species of 
phytoplankton produce powerful biotoxins, making them responsible for so-called “red tides,” or harmful algal blooms.
All this brings me to the latest Global CO2 Budget graphic shown below:
This graphic does not look like the one you have probably examined before. Those graphics were normally global CARBON budget. This one is global CARBON DIOXIDE budget. CO2 weight ratio to C is 44 to 12. To convert, multiply the C number by 3.67 to convert to CO2.
This chart would suggest that most of the O2 comes from the “land sink” rather than from the “ocean sink”. Error bars on the land sink are big. No big deal, as I suppose most of this is supposition anyway.
The followingxxxxxchart is interesting:
The chart balances emissions—fossil fuels and industry plus land use changes against sinks –land sink, ocean sink and the atmosphere. The ocean is absorbing more CO2. The land sink, since about 1950, has really increased, reflecting the “greening of the planet”.
cbdakota
- It is said that the plankton to krill to Blue whale is about as close a food chain connection as one can find. The Krill eat phytoplankton and the Blue whales eat krill. The blue whale can eat as many as 40 million krill per day or around 8,000 lbs. daily in order to power its massive body.
- “Plankton” is Sponge Bob SquarePants’ big enemy. Just another form of harmful species.
example, the sea level rise is predicated on a rise of temperature in the range of 4 to 7° C or greater by the year 2100. Without the big rise in global temperature, all these supposed disasters will not come to pass.
Climate Change Sanity 