(From Phys.org) — The pool of dissolved organic carbon (DOC) in the oceans is as large as all of the carbon in the atmosphere. Phytoplankton, which remove CO2 from the atmosphere and convert into more complex carbon compounds, are the primary source of DOC in the ocean.
Deep ocean DOC concentrations are almost constant throughout the world’s oceans and are thought to be resistant to biological breakdown. However, with the continuous DOC supply from the surface oceans, concentrations in the deep sea are not increasing.
Research published in the journal Nature Geoscience highlights the importance of deep ocean water circulation through hot hydrothermal systems as one of the main removal processes in this environment balancing the supply. The vent systems convert the biological resistant long-lived carbon into more readily available carbon, which organisms can then use.
Read the full article here: http://phys.org/news/2015-09-scientists-deep-ocean-carbon-riddle.html