Phytoplankton & CO2
Phytoplankton live in the surface, sunlit waters of the ocean. When they
grow and reproduce, they absorb CO2 and other chemicals from the water to
assemble new compounds essential to their life, such as those in cell walls,
in cellular energy stores, etc. When large phytoplankton blooms occur, the
surface waters become depleted in CO2. This disturbs the previous
equilibrium between ocean and atmosphere, and the ocean replenishes its
stocks of CO2 by absorbing more from the atmosphere, thus reducing the
greenhouse effect.
Most of the CO2-removal by phytoplankton growth is only temporary, for
instance ~95% of cells die and are decomposed in the same surface waters,
re-releasing their internal CO2 and negating the original CO2-reduction
effect. Only a small fraction (~5%) sinks to deeper in the ocean, where it
will remain out of contact with the atmosphere for 1000 years or so. A much
smaller fraction (~0.2%) sinks to the sea floor and eventually becomes part
of sedimentary rocks, where it is kept away from the atmosphere for millions
of years.
For more information see
1. Schlesinger WH 1991 "Biogeochemistry: an analysis of global change",
Academic Press, San Diego, CA, USA.
2. Butcher SS, Charlson RJ, Orians GH and Wolfe GV (eds) 1992 "Global
Biogeochemical Cycles", Academic Press, New York, USA.
Ehux
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Toby Tyrrell : T.Tyrrell@noc.soton.ac.uk