Circulation of carbon from the surface ocean to sediments, including hydrothermal plumes
Louis Legendre
Pierre and Marie Curie University Paris 6
Three vertical ocean carbon pumps have been known for almost three decades to
sequester atmospheric carbon in deep-water and sediment reservoirs, i.e. the solubility
pump, the carbonate pump, and the soft-tissue (also known as organic, or biological)
carbon pump. These three pumps maintain the vertical gradient in total dissolved
inorganic carbon between the surface and deep waters. The more recently proposed
microbial carbon pump maintain a gradient between short and long-lived dissolved
organic carbon (DOC; average lifetimes of <100 and >100 years, respectively).
Long-lived DOC is an additional proposed reservoir of sequestered carbon in the ocean.
In addition, Fe oxyhydroxide particles formed in hydrothermal plumes could carry
with them into the sediments significant amount of carbon from deep-ocean
DOC. This lecture examines critically various aspects of the four ocean carbon pumps, in
particular their physical dimensions and their mechanisms of carbon sequestration, and
it discusses the potential contribution of hydrothermal plumes to oceanic carbon
cycling at the deep seafloor.