Redfield-ratio

The cycles of carbon and the other main plant nutrients are coupled in a fundamental way by the involvement of these elements in photosynthetic assimilation and plant growth. Redfield (1934) and several others have shown that there are approximately constant proportions of C, N, S, and P in marine plankton and land plants ("Redfield ratios") see Chapter 10. This implies that the exchange flux of one of these elements between the biota reservoir and the atmosphere - or ocean - must be strongly influenced by the flux of the others. 

A TBma,) explicit functions of the available concentrations of the other nutrients. This approach allows for a pronounced interdependence between the fluxes of the different nutrients but it does not ensure that the Redfield ratios are maintained. In the second approach the contents of the nutrients in the biota reservoir are forced to remain close to the Redfield ratios. This method was used by Mackenzie et al. (1993) in their study of the global cycles of C, N, P, and S and their interactions. They were able to demonstrate how a human perturbation in one of these element cycles could influence the cycles of the other elements. 

Anderson, L. A. and Sarmiento, J. L. (1994). Redfield ratios of remineralization by nutrient data analysis. Glob. Biogeochem. Cycles 8,65-80. 

Takahashi, T., Broecker, W. S. and Langer, S. (1985). Redfield ratio based on chemical data from iso-pycnal surfaces. /. Geophys. Res. 90, 6907-6924. 

In addition to adsorption processes, phytoplankton can absorb (assimilate) certain nutrient metal ions (or metal ions that are by the organisms mistaken as nutrients). As with other nutrients, this uptake can occur in stoichiometric proportions. The uptake (and subsequent release upon mineralization) of nutrients in stoichiometric proportions was claimed already 1934 by Redfield. In referring to the atomic proportions C N P Si etc. one refers to the Redfield Ratios. This stoichiometry is well established (at least for the conventional nutrients) in oceanic waters it has also been postulated for lakes (Stumm and Morgan, 1970). 

Zhang, J.-Z., C.W. Mordy, L.I. Gordon, A. Ross, H. Garcia, M. Pahlow, and U. Riebesell. 2000. Temporal trends in deep ocean redfield ratios. Science 289 1839a. 

Stoichiometry is defined as the mass balance of chemical reactions as they relate to the law of definite proportions and conservation of mass. The Redfield ratio provides the most well-known example of stoichiometric distinction where the average atomic ratios of C, N, and P in phytoplankton are relatively consistent (106 16 1) in most marine species. 

Shifts in the stoichiometry of regenerated nutrients in sediments from the expected Redfield ratio has been suggested as an important factor controlling the metabolism of shallow estuaries. 

Concentration of DOC was converted from that of DON and the Redfield ratio. 

Selective changes in the relative abundance of bioactive elements delivered by rivers/estuaries also results in changes in the Redfield ratio, which can in some cases cause significant shifts in the composition and abundance of coastal phytoplankton. 

Redfield ratio a ratio originally used compared the ratios of C, N, and P of dissolved nutrients in marine waters to that of suspended marine particulate matter (seston) (essentially phytoplankton). 

The uptake of these nutrients into tissues occurs in constant relative amounts. The ratio (i.e., Redfield ratio) for C/N/P is 106 16 1. Silicate is utilised by some organisms, particularly diatoms (phytoplankton) and radiolaria (zooplankton), to form siliceous skeletons. Such skeletons... 

Stoichiometric analyses that have shown, relative to the availabihty of carbon (C), phosphorus (P), sificon (Si) and other nutrients, N often falls below the nutrient supply ratio needed to sustain balanced plant growth (i.e., Redfield ratio of 105 16 1 for C N P, Redfield, 1958 Smith, 1990)... 

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