Carbon cycle phytoplankton photosynthesis

Photosynthesis of terrestrial and aquatic plants, from tall trees to microscopic phytoplanktons, has a significant influence on the global carbon cycle. The better utilization of this biological process is clearly one of the solutions to cope with the rise in atmospheric GO 2 concentration and the possible global warming. 

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. 

The carbon cycle is not at all dependent on the presence of animals or plants. It could continue in the presence of micro-organisms alone and with special intensity in the oceans where the photosynthesis is eight times more intense than that due to land plants. This marine photosynthesis is due to the presence of Diatoms and the Dinoflagellates of phytoplankton. Figure 100 shows a carbon cycle which is entirely microbial in character. 

The conversions conducted in both steps are currently based on empirical relationships that are more or less robust. For example, the relationship between the chlorophyll and carbon content in an average phytoplankton cell is dependent on factors that influence cell metabolism, including nutrient arailability, temperature, and light. The temperature dependence of photosynthesis is associated with an enzyme-mediated step in the Calvin cycle (Figure 7.6a). 

Iron Fertilization of the Oceans. The intentional introduction of iron into the upper layers of certain areas of the ocean to encourage phytoplankton blooms is a form of CDR. The concept rehes on the fact that increasing certain nutrients—such as iron— in nutrient-poor areas stimulates phytoplankton growth. Carbon dioxide is absorbed from the surface of the ocean during the processes of photosynthesis when the phytoplankton, marine animals, and plankton die and sink in the natural cycle, that carbon is removed from the atmosphere and sequestered in the ocean s depths. 

The present model is based on mass balances for three main components representing phytoplankton (A), nutrients (E), and organic phosphorus (C), which can describe phosphorus cycle within a water body as follows. Phytoplankton biomass is produced by the photosynthesis reaction, consuming nutrients (in lakes and reservoirs, the limiting nutrient is phosphorus) and dissolved carbon dioxide, with solar radiation and adequate temperature. Upon death, phytoplankton biomass increases the pool of organic phosphorus, which is in turn converted to phosphate by mineralization bacteria. The model has several kinetic parameters that have to be estimated based on collected data from the specific reservoir under study. 

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