| |
Communication at the NABS Annual meeting, Keystone, 2000
(323) AMMONIFICATION, NITRIFICATION, AND DENITRIFICATION IN SHINGOBEE RIVER SEDIMENTS, MINNESOTA: THEIR COMBINED AFFECT ON SEASONAL SURFACE WATER CHEMISTRY.
J.H. Duff1, F.J. Triska1, R.J. Avanzino1, A.P. Jackman2, and R.W. Sheibley III2. 1U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025, 2University of California, Department of Chemical Engineering, Davis, CA 95616
Due to its role in biosynthesis, inorganic N is an important component in lotic environments. Microbial processes can influence inorganic N availability for channel biota, in part by regulating the oxidation state of N in sediments. In the Shingobee River, groundwater discharge through the streambed is an important source of available N in the channel. Large fluctuations of ammonium and nitrate occur in the channel between summer and winter. To examine the seasonal effects of microbial processes on N availability, we measured ammonification, nitrification, and denitrification in sediment enzyme assays. We found that retention and transformation of DIN by microbial processes was constrained by fluctuation in water temperature. During winter, when the surface of the streambed dropped below 1 oC, ammonification rates decreased by 75% (85 to 20 ng N/cc sed/h) and nitrification rates decreased by 60% (115 to 45 ng N/cc sed/h). Denitrification rates were suppressed by 95% in the winter (306 to 15 ng N/cc sed/h), possibly do to elevated DO levels in the sediment in addition to low temperature. Lower rates of inorganic N cycling in sediments during winter resulted in significantly higher concentrations of both ammonium and nitrate in the channel.
Presented at 3:15 PM on Thursday, June 1, 2000 in Groundwater and Surface Water Interactions II
|
|
