starch) can be transferred from leaves to rhizomes for long-term storage. The higher variability is due to tissue differentiation: compounds involved in photosynthesis and carbon fixation are primarily in the leaves and not in the roots. Moreover, there is much more variability in the composition of benthic primary producers, particularly in macrophytes. The composition of seagrasses and, in particular, emergent saltmarsh vegetation and mangrove trees deviates from unicellular primary producers: higher C:N and C:P ratios, less proteins and nucleic acids and more structural carbohydrates and lignins. Individual species may deviate from ideal or revised Redfield ratios, but over larger spatial and temporal scales these differences average out. The composition of marine particles is rather uniform because phytoplankton and bacteria (and their remains) dominate plankton, and these organisms are primarily made up of proteins (>50%) supplemented by lipids, carbohydrates, nucleic acids and pigments. This lower oxygen content has consequences for the O 2:C respiration coefficient. 2002) rather than C 106H 260O 106N 16P of the ideal Redfield ratio. 2002), arrive at average compositions of C 106H 175O 42N 16P (Anderson 1995) and C 106H 177O 37N 16PS 0.4 (Hedges et al. Estimates of marine organic matter based on mixing of proteins, lipid, carbohydrates and nucleic acids and using modern analytical tools (Anderson 1995 Hedges et al. Moreover, there is also hydrogen loss during the transformation of the NH 3-group in ideal Redfield organic matter to the NH-amide group in proteins. Hydrogen and oxygen loss results from dehydration, wherein CH 2O is transformed into CH 2 chains in proteins and lipids. While simple carbohydrates are the first molecules formed during carbon fixation, the biosynthesis of proteins, lipids and polysaccharides results in the loss of hydrogen and oxygen. 6.1 and 6.2 is that it simplifies marine organic matter into an elementary carbohydrate (CH 2O), whereas newly produced marine organic matter is better represented as a mixture of proteins (~65%), lipids (~19%), and carbohydrates (~16%) and other compounds (pigments and nucleic acids Hedges et al. The problem with the traditional Redfield ratios as formulated in Eqs. Primary production based on nitrate (new production) or ammonium (recycled productions) has consequences for the quantity of oxygen released. The O 2:C coefficient for aerobic respiration (including nitrification) is thus 1.3. These RKR equations indicate that 138 units of oxygen are required for oxidation of one mole of Redfield organic matter: 106 oxygen molecules to convert CH 2O to CO 2 and 32 oxygen molecules to convert the NH 3 all the way to HNO 3. ( 1963) presented the (canonical) overall reaction for marine organic matter production: Moreover, they have shown that N and P limitation during cell growth results in N:P ratios below or above the Redfield ratio, respectively. Loladze and Elser ( 2011) have shown that protein and ribosome synthesis results in a protein:rRNA ratio of ~3, which corresponds to an atomic N:P ratio of 16, as observed in the ocean for plankton. At the cellular level, nitrogen is primarily used for the construction of proteins and phosphorus for the synthesis of ribosomal ribonucleic acids (rRNA). The original Redfield ratio has been extended to include other elements and heterotrophic organisms (ecological stoichiometry) and has been related to cellular level and global scale processes (Falkowski 2000 Sterner and Elser 2002 Box 6.1). They are used in reconstruction of anthropogenic carbon inventories and are in the equations underlying Earth System modelling (Sarmiento and Gruber 2006). Redfield ratios have shown useful in a wide range of topics, from nutrient limitation to biogeochemical modelling in the present and past ocean. ( 1963), at 106C:16 N:1P, has been validated by thousands of observations, and the overall ratios appear to be robust. The Redfield ratio as formalized by Redfield et al.
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