Assimilable organic carbon, dissolved

The carbon cycle in seas involves the assimilation of carbon dioxide dissolved in sea water by the phytoplankton with a simultaneous oxygen release. Zooplankton and fish use this oxygen for the respiration. During the organic matter decomposition, CO2 is supplied into the atmosphere. On land, the exchange of carbon dioxide with the atmosphere is accomplished by respiration, photosynthesis and by the combustion of fossil fuels. 

I.C. Escobar, S. Hong and A. Randall, Removal of assimilable and biodegradable dissolved organic carbon by reverse osmosis and nanofiltration membranes, J. Membr. Sci., 175 (2000) 1-17. 

To increase the reliability of assessing the role of the World Ocean in the global carbon cycle, a more detailed description is needed of the production processes in ocean ecosystems. Along with the physical and chemical processes of transformation and motion of carbon in the ocean medium, the biological processes play an important role. In particular, phytoplankton, just like the nutrient elements, assimilates dissolved C02 from saltwater. As a result, an organic substance is formed that partially goes to the nutrient chains of the trophic pyramid of a given basin of the World Ocean and partially descends to bottom sediments. The totality of all the... 

Williams, P. J. leB. (1995). Evidence for the seasonal accumulation of carbon-rich dissolved organic material, its scale in comparison with changes in particulate material and the consequential effect on net C/N assimilation ratios. Mar. Chem. 51, 17-29. 

Carbonates occur in natural waters at higher concentrations only very rarely. Concentrations which can be analytically determined are formed during intensive photosynthetic assimilation of green organisms in waters when dissolved CO2 is exhausted and thus, the carbonate equilibrium is shifted in favour of the formation of CO3 ions. By this process the pH value is increased (pH > 8.3). 

Figure 3. Idealized carbon isotope cycle in a small stratified lake. The isotopic composition of organic matter buried in sediments is determined by the proportions of different terrestrial and lacustrine organic mailer. Ihccartron isotopic composition of dissolved inorganic carbon (DlC), and the rates of primary production and respiration within the water column. Isotope enrichment factors (e), listed here as the difference between the product and the substrate, vary with the form of DlC that lake algae assimilate (e.g., C02(aq) or HCOy ). Inorganic carbonate (CaC03> typically forms in isotopic equilibrium with the dissolved inorganic carbon pool and. as such, is indirectly affected by organic matter sources and primary production and respiration rales.

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