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Nitrification in Sediments of Selected Wisconsin Lakes¹

ABSTRACT

Nitrification rates in lake sediment-water systems were investigated in the laboratory. Samples from Wisconsin eutrophic and oligotrophic hard- and soft-water lakes were incubated at 10C or 25C in the dark using nonstirred (i.e. quiescent) and stirred (magnetic stirrer) systems open to the atmosphere. Nitrate was not formed in the acid sediments from soft-water lakes. However, in calcareous sediments from hard-water lakes, nitrification proceeded readily when the systems were stirred to increase oxygen diffusion. Nitrate did not accumulate when the samples were not stirred. Experiments with N-Serve indicated that autotrophic organisms were mainly responsible for nitrification in the Lake Mendota samples.

Considering the high oxygen diffusion rate required for nitrification in sediments, it is likely that this process occurs only at the sediment-water interface in oxygenated waters.

Key Words: Eutrophication • N cycle • dissolved oxygen • N-Serve

¹ Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison, and by a grant from Federal Water Quality Administration, U. S. Dep. Int., Grant no. 16010 EHR. Published with the approval of the Director, Research Division, College of Agricultural and Life Sciences, University of Wisconsin, Madison 53706.

² Research Assistant and Associate Professor, Department of Soil Science, and Research Specialist, Wisconsin Department of Natural Resources, respectively.

Received for publication April 29, 1971.