HR: 09:45h
AN: NB31D-06    [Abstracts]
TI: Temporal Patterns in Sediment Denitrification Rates in an Agricultural Stream
AU: * Royer, T V
EM: troyer@kent.edu
AF: Kent State University, 256 Cunningham Hall, Kent, OH 44242 United States
AU: Tank, J L
EM: tank.1@nd.edu
AF: University of Notre Dame, Galvin Hall, Notre Dame, IN 46556 United States
AU: David, M B
EM: mbdavid@uiuc.edu
AF: University of Illinois, Turner Hall, Urbana, IL 61801 United States
AB: Denitrification is an important component of the nitrogen cycle in streams, representing a true nitrogen sink. Few long-term studies of stream denitrification have been made, making it difficult to identify factors responsible for temporal patterns in denitrification rates. We measured denitrification, water chemistry, and sediment and hydrological characteristics in an Illinois stream for two years during all seasons. Denitrification rates spanned nearly 3 orders of magnitude, from 0.05 to 25 micrograms N/g AFDM/hr. The mean (n=16) was 7.0 micrograms N/g AFDM/hr, with a coefficient of variation of 115%. Sediment characteristics (total C, N, C:N) varied little during the study, and did not explain temporal variation in denitrification rates. Nitrate-N (range = 0.6 to 14 mg/L), water temperature, and discharge varied substantially during the study, but were not correlated with denitrification rates. DOC explained 39% of the variation in denitrification rates, if both variables were log-transformed. These results suggest that sediment denitrification was not directly controlled by characteristics of the water column or standard measures of sediment quality, or these variables were not measured at a relevant spatial scale. Variation in denitrification rates may reflect microbial population changes or community interactions that are not accounted for with typical environmental variables.
DE: 1845 Limnology
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly