Carbon cycling potential from Utricularia breviscapa decomposition in a tropical oxbow lake (São Paulo, Brazil)

The rate of decomposition of aquatic macrophytes is controlled by environmental factors such as temperature and oxygen availability. Laboratory assays were carried out to evaluate the decomposition rates of Utricularia breviscapa under controlled conditions of dissolved oxygen and temperature. Measured decomposition rates were then used in model simulations of expected decomposition rates using field collected monthly temperature and dissolved oxygen measures. The incubations were comprised of U. breviscapa detritus added to Óleo Lagoon water under aerobic and anaerobic conditions at 15.3 °C, 20.8 °C, 25.7 °C and 30.3 °C in the dark. Mass loss and leachate formation were monitored over 180 days. Overall, the decomposition process was faster under aerobic than anaerobic conditions and by increasing at higher temperature. Considering the seasonal changes of temperature and oxygen availability of Óleo Lagoon, the simulated values of mineralization rates of dissolved organic carbon (DOC) and refractory particulate organic carbon (POCR) suggest faster carbon cycling in November. Based on these simulations, in the cold months (June and July) the DOC and COPR mineralization processes were 22% and 25% lower than in the warmer months (October and November), respectively. On average, the DOC mineralization process was 3.7 times faster than POCR.