Research Foci
Physiology and Genetics of Nitrifying Bacteria
Environmental Controls on N2O Production by Nitrifying Bacteria
Nitrifying Bacteria and d18O signatures of NO3- in the Ocean
Isotopic Signatures as Indicators of Nitrification & Denitrification
Sources of N2O in Past Ocean Ecosystems
Do-Evolution of Organisms and Environment

Sources of N2O in Past Ocean Ecosystems

The balance of the nitrogen cycle in the present ocean and over glacial/interglacial timescales is a question of great interest. As nitrogen can be a limiting nutrient to ocean primary productivity and export production, changes in the supply of nitrogen may impact climate through altering the biological drawdown of CO2. There is strong evidence for changes in the rate of denitrification in the three main oxygen minimum zones on glacial/interglacial timescales, with characteristically lower denitrification rates during glacial periods. The concentrations of N2O in the atmosphere also are lower during glacial periods than during intervening warm periods. I am interested in exploring a possible connection between the strength of marine denitrification and N2O concentrations/isotopic signatures in the atmosphere. Using concentrations and stable isotope signatures of N2O trapped in ice cores, we may be able to add an additional constraint on the strength of water column denitrification and/or surface nitrification (driven by productivity) during glacial/interglacial periods and transitions.


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