Coupled Biogeochemical Cycles in Rivers
Much of our research in rivers addresses interactions among the carbon (C), nitrogen (N), and phosphorus (P) cycles. Specifically, we have been interested in relative importance of and interactions between primary production (photosynthesis that leads to plant growth) and removal of N by the process of denitrification (reduction of NO3 to N2 gas by heterotrophic microbes). In both desert streams and spring-fed rivers, we have found that despite the high productivity of these systems, the largest influence of vegetation is to stimulate denitrification by the introduction of organic matter and reduction of sediment oxygen concentrations. This work has included spatial surveys, greenhouse experiments, and analysis of high-frequency time series of metabolism and N concentration. More recently, we have expanded our use of in situ sensors to include diel variation in P as well as O2 and NO3. We have also used natural gradients in dissolved organic matter to understand how these inputs from terrestrial systems influence the N cycle in aquatic systems.
Our current grants supporting this work are nearing their end, but we have several proposals in preparation to extend various aspects of this work, including to NSF and the St. John's River Water Management District.
Our current grants supporting this work are nearing their end, but we have several proposals in preparation to extend various aspects of this work, including to NSF and the St. John's River Water Management District.
