Science Serving Maryland's Coasts
Jeffrey Cornwell, Ph.D.
Horn Point Laboratory
Effects of Various Sample Containment Methods on the Measurement of Denitrifiction
Increasing amounts of studies are focusing on the role of denitrification in the determination of the total amount of N in an ecosystem, particularly in estuarine environments. Consequently, the methods of measurement and analysis have recently come under close analysis. There is debate over the "best" method for measurement - three of the major methods being acetylene inhibition, r5N isotope tracer, and N2 flux. Everyone's main goal is to find the most accurate method using the simplest procedure. This experiment proposes that it is possible to make sampling for denitrification easier by using the smallest size core that will give accurate results. This was tested using the N2 flux method and sediment collected from a MEERC research tank. The sediment was collected and incubated with stirring overnight. The following day some of the cores were subcored and all cores were sampled along a time course to allow the measurement of rate of denitrification. The 3" and 4" continued to be stirred but the 1" was no longer stirred. It was found that although the 3" and 4" showed comparable results, the 1" cores were significantly different. This was not our hypothesized result, but it does lead us to believe that smaller cores that are not stirred are not suitable at this time for denitrification measurement using the N2 flux method. Because of some experimental variability (especially the fact that the 1" cores were not stirred) additional studies are recommended.
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