Jornal de Ecossistema e Ecografia

Abstrato

Global Redox Carbon Cycle and Photosynthesis Development

Ivlev AA

The principle of actualism and recent findings on carbon isotope fractionation in photosynthesis, combining with data on isotopic ratio of carbon in sedimentary rocks in form of carbonates and coeval organic matter allowed developing a new model of the redox carbon cycle. According to the model, carbon transfer between biosphere and geospheres is a conversion of the element from the oxidized state to the reduced one, and back. The transfer proceeds under the control of photosynthesis, which is an essential element of the carbon cycle. The lithospheric plates’ movement exerts impact on photosynthesis development via periodic injections of CO2 into “atmosphere – hydrosphere” system during plates’ collisions. Due to irregular lithospheric plates’ movement the orogenic cycle consists of a short-term orogenic period of active volcanism, magmatism and mountain building and a long-term geosynclynal period of low volcanic activity and quiet development of Earth crust processes. In short-term orogenic periods, when plates move fast and collide frequently, a great amount of CO2 evolves from the subduction zones of the Earth’s crust (where plates collide) and fills the “atmosphere – hydrosphere” system. It causes expansion of photosynthesis. At the same time oxygen concentration drops due to oxidation of reducing magmatic rocks. In longterm geosynclynal period, due to photosynthesis, the CO2 concentration gradually drops whereas O2 concentration increases and achieves the maximum by the end of the cycle. In the following relatively extended geosynclynal periods, the collisions of plates are seldom, and the rate of CO2 emission from subduction zones becomes weaker than the rate of CO2 assimilation. The pulsating movement of plates exerts an impact on dynamics and development of photosynthesis. It, in turn, determines periodicity of numerous processes, including climatic cycles, changes in the rate of biodiversity, irregular accumulation of organic matter in sediments, uneven stratigraphic oil distribution, sea level changes, etc. The redox carbon cycle is a self-organizing system due to negative feedback between CO2 assimilation and photorespiration in response to oxygen growth. It made carbon cycle to shift to ecological compensation point. In this point the system become sensitive to separate plates’ collisions what results in shortterm climatic oscillations.