Theoretical limits of oxygen: carbon and oxygen: nitrogen ratios during photosynthesis and mineralisation of organic matter in the sea

• Autores: Fernando Fraga, Aida Fernández Ríos, Fiz Fernández Pérez, Francisco Gómez Figueiras
• Localización: Scientia Marina, ISSN 0214-8358, Vol. 62, Nº. 1-2, 1998, págs. 161-168
• Idioma: varios idiomas
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• Resumen

  • It is frequent to observe disagreements between the relationships RC =-?O2/?C and RN = -?O2/?N found during photosynthesis-mineralisation studies in the ocean and those expected according to the Redfield plankton composition. That is because RC and RN depend on the C/N and Carbohydrates/Lipids ( Cbh/Lip) ratios of the organic matter. Starting from the mean biochemical composition of the main groups of phytoplankton biomolecules and from the stoichiometry of photosynthesis-mineralisation, we establish a new formulation to enable us to calculate RC and RN as a function of C/N and Cbh/Lip ratios independent of the variance in the N/P ratio. The approach proposed here permits the theoretical limits of RC and RN to be calculated. The RC value can vary between 1 and 1.58 while RN can vary between 5.8 and infinity with the interrelationships between the ratios being defined by RN/RC=C/N which, in its turn, can vary between 3.67 and infinity. For a given RC the limits of RN become narrower and vice versa. When C/N ratio is fixed the limits of the RC and RN values also become narrower. A graphic representation to check and visualise these limits and other experimental biochemical composition values is developed. According to the average value of the Cbh/Lip relationship, 0.82 in carbon, recovered from the literature and for a C/N = 106/16, the estimate mean RC and RN values are 1.41 and 9.33 respectively which are coincident with previous ratios given by other authors.