The carbon and oxygen cycles

The subsequent oxidation of the organic compounds produced in photosynthesis is coupled with the reduction of molecular oxygen back to water. The most direct means by which this is achieved are combustion and respiration in which organic carbon is converted back to carbon dioxide. Algae and plants, as well as the animals that feed on them, contribute to respiration. 

The bacteria and fungi oxidize the bulk of organic matter. Three general routes of catabolism ( breaking down ) of organic compounds are used by microorganisms  

The microbiology of accidental or routine oil discharges into aquatic environments has been reviewed by Bartha and Atlas [7]. Some of the observations quoted in their review deserve to be mentioned in relation to the environmental carbon cycle, as follows. 

Most of the increases in microbial populations were associated with chronic inputs of petroleum hydrocarbons. Petroleum hydrocarbons can limit the growth of bacteria in sediment and water in non-oil contaminated estuarine ecosystems, and may also result in selective decreases in algal and protozoan populations. Not all microbial populations increase or decrease in response to the addition of petroleum hydrocarbons some microorganisms show a neutral response to certain hydrocarbons, and, in these cases, population size of these organisms remains unchanged. 

The genera of aquatic hydrocarbon degraders reported by various workers are listed in Table 4.9. 

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The Flow of Energy in the Biosphere and the Carbon and Oxygen Cycles Are Intimately Related... 

FIGURE 18.3 The flow of energy in the biosphere is coupled primarily to the carbon and oxygen cycles. 

Photosynthesis adds oxygen to the atmosphere. Oxygen is a component of biomass in the biosphere and most rocks in Earth s crust are composed of oxygen-containing compounds. With its chemical formula of H2O, water in the hydrosphere is predominantly oxygen. In addition to the carbon and oxygen cycles described above, three other important life-element cycles are those of nitrogen, sulfur, and phosphorus ... 

Feedbacks Between the Nitrogen, Carbon and Oxygen Cycles... 

Evolutionary History of the Nitrogen, Carbon, and Oxygen Cycles 1537... 

Biological feedbacks to the global nitrogen, carbon, and oxygen cycles 1549... 

Biological feedbacks into the global nitrogen and oxygen cycles are intricately dependant on cfimate patterns and oceanic circulation which also influence trace metal availabifity in the upper ocean (Fig. 35.5). In this section we explore future scenarios in the oceanic nitrogen, carbon and oxygen cycles due to shifts in aeolian iron availabifity, variations in climate, and ocean circulation. 

Schidlowski M., Appel P. W. U., Eichmann R., and Junge C. E. (1979) Carbon isotope geochemistry of the 3.7 X 10 yr-old Isua sediments, West Greenland implications for the Archaean carbon and oxygen cycles. Geochim. Cosmochim. Acta 43, 189-199. 

Schidlowski M. and Junge C. E. (1981) Coupling among the terrestrial sulfur, carbon and oxygen cycles numerical... 

Figure 1.5 extends this notion to the geochemical level which shows an estimate of the influence of the global biosphere carbon and oxygen cycles on the fluxes of major elements through the terrestrial reservoirs, and includes the effects of both primary and secondary biogeochemical processes. 

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