Biological pump
A common method is to estimate primary production fuelled by nitrate and ammonium as these nutrients have different sources that are related to the remineralisation of sinking material. Presently, about one third (approximately 2 Gt C y-1). However, climate change may affect the biological pump in the future by warming and stratifying the surface ocean.Applying the results of local studies to the global scale are complicated by the role the ocean s circulation plays in different ocean regions. The biological pump has a physico-chemical counterpart known as the solubility pump. In reference to the different use of these materials in organisms, the organic carbon portion of this transport is known as the soft tissues pump, while the inorganic carbon portion is known as the hard tissues pump. In the case of organic material, remineralisation (or decomposition) processes such as bacterial respiration, return the organic carbon to dissolved carbon dioxide.
From these it is possible to derive the so-called f-ratio, a proxy for the local strength of the biological pump. Calcium carbonate dissolves at a rate dependent upon local carbonate chemistry.
For an overview of both pumps, see Raven & Falkowski (1999). Land-use changes, the combustion of fossil fuels, and the production of cement have led to a flux of CO2 to the atmosphere. Also, changes in the ecological success of calcifying organisms caused by ocean acidification may affect the biological pump by altering the strength of the hard tissues pump. .
As these processes are generally slower than synthesis processes, and because the particulate material is sinking, the biological pump transports material from the surface of the ocean to its depths. As the biological pump plays an important role in the Earth s carbon cycle, significant effort is spent quantifying its strength. It is believed that this could decrease the supply of nutrients to the euphotic zone, reducing primary production there.
However, because they occur as a result of poorly-constrained ecological interactions usually at depth, the processes that form the biological pump are difficult to measure. The former is a component of all organisms, the latter only of calcifying organisms, for example coccolithophores, foraminiferans or pteropods.
In oceanic biogeochemistry, the biological pump is the sum of a suite of biologically-mediated processes that transport carbon from the surface euphotic zone to the ocean s interior. The organic carbon that forms the biological pump is transported primarily by sinking particulate material, for example dead organisms (including algal mats) or faecal pellets. However, some carbon reaches the deep ocean as dissolved organic carbon (DOC) by physical transport processes such as downwelling rather than sinking. Carbon reaching the deep ocean by these means is either organic carbon or particulate inorganic carbon such as calcium carbonate (CaCO3).
