Sack Lunch Seminar (SLS)

Abstract: Fixed nitrogen availability can regulate atmospheric carbon dioxide concentrations and climate as a whole. Its loss via two anaerobic microbial processes – anammox and denitrification – only occurs where oxygen is sufficiently depleted. Field experiments in the tropical Pacific oxygen minimum zone resolve two long-standing debates critical to understanding global climate. While very low oxygen concentrations are required for fixed nitrogen loss by either anammox or denitrification, organic matter quantity and quality determine the magnitudes of these rates and the partitioning between the two pathways. Dissolved oxygen concentrations also decouple the denitrification steps, allowing for net production of nitrous oxide and accentuating the importance of the oxygen and nitrogen cycles in regulating climate.