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

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