The effects of sediment desiccation on the potential for nitrification, denitrification, and methanogenesis in an Australian reservoir

La Trobe University Faculty of Science, Technology and Engineering Murray Darling Freshwater Research Centre

MDFRC item.

Sediments from an Australian reservoir were selected for varying degrees of in situ desiccation (i.e. non-desiccated, partially desiccated and desiccated). Sediment samples were then chemically amended with appropriate electron donors and acceptors to ascertain the effect of sediment desiccation on the potential for nitrification, denitrification, methanogenesis, and the interaction of these processes. There was no detectable nitrification in these sediments yet up to 75% of added nitrate was converted to dinitrogen. Denitrification was predominantly limited by nitrate although there was evidence of carbon co-limitation. None of the nitrogen cycle processes were notably affected by sediment desiccation. There was no flush of mineral nitrogen from desiccated sediments upon rewetting. Methanogenesis did not begin in these sediments until nitrate concentrations fell below 2.25 * 10-5 M. Methanogenesis was always carbon limited. Methanogens were affected by sediment desiccation but were capable of recovery over time upon rewetting of sediments.