1. The Biosphere Total mass of organic carbon in the biosphere : 5E18 g C 20% in living organisms 80% compounds arising from the decay of living organisms (e.g. humus) Sum total of all living and dead organisms in the Earth system

2. Composition of the biosphere Importance of C,H,O Simplification : A generic chemical formula to represent the composition of the bisophere as the stoichiometric equivalent of glucose. Glucose is the ‘building block’ from which other molecules are synthesized in the biosphere. “CH 2 O”Glucose: C 6 H 12 O 6 Other important elements (nutriments) : N, P trace elements (oligo-elements) Biospheric molecule

3. Metabolic processes Autotrophism (photo,chemo) : Synthesis of living protoplasm from minerals (require energy) Heterotrophism (chemo): Synthesis of living protoplasms from organic molecules Biosynthesis (or anabolism) : construction of living protoplasm (living content of a cell) Catabolism: breaking down of organic polymers as a source of energy 2 Photosynthesis Respiration or decay of organic matter

4. Oceanic biosphere The Redfield ratio : represents the average ratio between C,N,P in the ocean biota. It is currently estimated to be 106:16:1 N and P are essential nutrient that have to be introduced in the simple photosynthesis / respiration –decay reactions photosynthesis respiration is replacing “CH2O” However part of H20 generated is released in the environment and lower the content of O and H in the organic polymers. To account for that it is assumed that biomass is synthetised by combining CO2 and H2O is ratio greater than 1:1, e.g 106:64. Finally a more representative equation could be:

5. Continental biosphere The mass of continental biosphere is dominated by tree, rich in lignine and have lower O:C, H:C, and N:C ratios than marine biomass. The budget between photosynthesis and respiration could be written as : Continental “biospheric molecule”

6. Primary production Rate at which C is assimilated or fixed by green plants. Fundamental parameters in Biogeochemical cycles. Gross primary production rates (GPP): Total C assimilated by green plants Net primary production (NPP): Account for respiration loss For terrestrial biosphere, about 50% of the GPP is estimated to stay in the biosphere as NPP (global scale estimation). LF: litter fall D: decay GSOP: gross surface oceanic prod. NSOP: Net surface oceanic prod. U: Upwelling S: Sedimentation Rp: respiration in the photic zone NPP = GPP - Rgp