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Microscopic plankton comes in animal and plant forms. The plants are known as phytoplankton. They lie at the base of the marine food chain because they convert sunlight and carbon dioxide into organic carbon - food for everything else.

Smaller animals such as shrimp-like krill feed on plankton and are themselves eaten by larger organisms, from small fish to the biggest whales. Without phytoplankton, the oceans would soon become marine deserts. Phytoplankton are also important because of the role they play in the carbon cycle, which determines how much carbon dioxide - the most important greenhouse gas - ends up in the atmosphere to cause global warming. Huge amounts of carbon dioxide from the atmosphere, which dissolves in the oceans, are absorbed by phytoplankton and converted to organic carbon. When the phytoplankton die, their shells and bodies sink to the seabed, carrying this carbon with them.

Phytoplankton therefore acts as a carbon "sink" which takes carbon dioxide from the atmosphere and deposits the carbon in long-term stores that can remain undisturbed for thousands of years. If the growth of phytoplankton is interrupted by global warming, this ability to act as a buffer against global warming is also affected - leading to a much-feared positive feedback.

The earth is a living, breathing planet due to photosynthesis. Ocean photosynthesis may become even more important if we further reduce photosynthetic capacity of land surface plants. Photosynthesis is the most important photochemical process on earth because it is through this process that mineral non-living matter uses light energy from the sun to store energy in living matter that feeds all but a few of the other living organisms on the entire planet.

Scientists have developed a new way of determining from satellite images the amount of photosynthesis in the ocean. As compared to previous measurements, the new values are sometimes different by a factor of two or more, depending on the region. Warmer surface water caused by global warming causes greater temperature stratification, with warm surface layers sitting on deeper, colder layers, to prevent mixing of nutrients.

"Scientists have been trying to determine global primary production for a long time," said Michael Behrenfeld of Oregon State University, in a NASA-sponsored teleconference.

Why does NASA care about...phytoplanton? Shouldn't they be pointing their telescopes, space?

It's big business for nature. Although invisible to the naked eye, phytoplankton account for the production of more than 50 billion tons of organic material each year. And because these floating plants absorb as much of the atmosphere's carbon dioxide - a major greenhouse gas - as do terrestrial plants, they are important to any global climate study.

Even though they make up just a small fraction of the total photosynthetic biomass on earth, scientists estimate that phytoplankton organisms are responsible for approximately 40 percent of the planet's total annual photosynthetic output. Amazing, considering they are largely out of sight, and seemingly out of the general thoughts of the populace of Earth.

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