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The biological pump
The biological pump is the process where CO2 that is captured from the atmosphere is transferred through various marine food webs to oceanic sinks where it contributes to permanent CO2 sequestration. While primary production through phytoplankton blooms, being the lowest trophic level of the marine food chain, does represent the largest organic biomass in ocean systems, it is a labile source of organic carbon being rapidly digested by either bacteria or the next trophic level of secondary production representing the zooplankton. This secondary production, does the bulk of the CO2 draw down in ocean basins. This draw down takes place in upwelling areas where sediments are rich in exoskeleton fragments of chiefly copepods and their dormancy eggs. Copepods, have 12 metamorphosis a year, each time shedding their exoskeletons. This exoskeleton is refractory as it is composed of alternating layers of aragonite and chitin, each requiring a different type of decomposers while they settle down through the water column. Copepods also produce large quantities of eggs designed to overcome longer periods of dormancy. The importance of upwelling areas for the draw down of organic carbon is particularly striking when observing the Mauna Loa diagram, where in December during a La Niña year, the balance between ocean CO2 degassing and draw down results in a CO2 increment to the atmosphere of only 2 ppm, while when during an El Niño year when the CO2 draw down does not take place as upwelling does not take place, the atmospheric increment is of 3 ppm, thus indicating that a healthy cold water upwelling system can draw down 1 ppm of CO2 per year.

Van Waveren, I.M., Visscher, H., 1994. Analysis of the composition and selective preservation of organic matter in surficial deep–sea sediments from a high–productivity area (Banda Sea, Indonesia). Palaeogeography, Palaeoclimatology, Palaeoecology, 112: 85–111.