Nutrient cycling in a simulated pond ecosystem.

Mathematical modeling of ecosystems requires a considerable amount of knowledge about the subsystems functioning within the broad framework and the various rate processes and transfer coefficients that control the dynamic aspects. A detailed analysis of the transfer rates and budget of inorganic carbon and nutrients in a simulated pond was conducted for assessment and comparison with aquatic bodies that undergo cultural eutrophication. In these systems the processes are complicated by a variety of inputs. Such inputs interfere with the assessment of lake background conditions and water quality. We used the compartmental model of biogeochemical cycling to calculate transfer rate of inorganic carbon and nutrients through various processes. The major external variables or forcing functions considered were light and temperature, while the state variables included the biotic and the abiotic compartments. The major processes studied were: photosynthesis, respiration and decomposition that play an important partin balancing the nutrient content of the system and maintain a dynamic equilibrium. The study illustrates how computational modeling studies are useful for analysis and management of systems for control and optimization of processes. The system shows a perfect cycling of carbon and the rate of withdrawal is equal to the return keeping the system in balance. About 0.284 m moles l(-1) is withdrawn from the reservoir for primary production each day and returned back through respiration and decomposition. The concentration of nitrates and phosphates resonate in tune with the utilization of carbon and productivity.