Modelling Changes in the Carbon Chemistry of the Aquatic Media during Photosynthesis

Mathematical modeling of systems requires a considerable knowledge about the subsystems, and the various rate processes and transfer coefficients that control the system. One such system involves changes in the carbon chemistry of the aquatic media during photosynthesis because inorganic carbon is a potentially limiting factor in the aquatic media. We used two artificial systems: an aquarium and a pond system with Hydrilla as the major photosynthetic organism to study the changes in the carbon chemistry and the carbon species taken up. The study depicts that carbon dioxide is the major molecular species taken up and in its absence; free carbon dioxide is released initially from the dissociation of bicarbonate ions rather than its direct use. The rate of entry cannot be accounted directly by diffusion alone because of the pH gradients in and out of the cell, and therefore carbon concentrating mechanisms and aquaporins  are thought to be involved in the process. The study gives a clear picture of the amount of carbon dioxide available in the free form and the amount released from bicarbonate ions and used in photosynthesis, and can be accounted perfectly.