Abstract


LAKE NITROGEN CYCLING DYNAMICS EXPLORED WITH ISOTOPE TRACING AND MATHEMATICAL MODELING

Nitrogen biogeochemistry is intimately coupled to phytoplankton ecology (e.g. nitrogen fixing vs. non-nitrogen fixing cyanobacteria). We use isotope tracing and mathematical modeling to understand nitrogen dynamics in Lake Taihu, China, which is plagued by cyanobacteria blooms. A three-dimensional hydrodynamic model is coupled with a biogeochemical model, which has two sediment layers and state variables for multiple phytoplankton (with variable nutrient quotas) and various nutrients, including the nitrogen species PON, DON, NH4, NO3, NO2 and phytoplankton N, all for nitrogen-14 and -15, and processes for nitrification, denitrification, phytoplankton uptake and excretion, ammonia regeneration (DON>NH4), and DNRA. We use the full model to simulate the whole lake. The laboratory sediment core incubations experiments were spiked with 15NO3 and produce “potential” rates, which are not directly comparable with the full lake model. Therefore, we use the same model (without hydrodynamics) to simulate each core experiment, calibrate the rate constants to the observations and then use those parameters in the full model. The core incubation simulations as in the actual experiments, they take their initial conditions directly from the whole lake model.

Authors

Fredrick, N. D., Northeastern University, USA, fredrick.n@husky.neu.edu

Li, W., Nanjing Institute of Geography and Limnology, China, liwei@niglas.ac.cn

McCarthy, M. J., University of Texas Marine Science Institute , USA, mjm.kingston@gmail.com

Zhu, G., Nanjing Institute of Geography and Limnology, China, gwzhu@niglas.ac.cn

Qin, B., Nanjing Institute of Geography and Limnology, China, qinbq@niglas.ac.cn

Gardner, W. S., University of Texas Marine Science Institute , USA, wayne.gardner@utexas.edu

Hellweger, F. L., Northeastern University, USA, ferdi@coe.neu.edu

Details

Oral presentation

Session #:060
Date: 5/23/2014
Time: 14:15
Location: B 110 - 112

Presentation is given by student: Yes