Virginia Institute of Marine Science
Global Biogeochemical Cycles
Biogeochemical rate processes in the Arctic are not currently well constrained, and there is very limited information on how rates may change as the region warms. Here we present data on the sensitivity of ammonium (NH4+) uptake and nitrification rates to short-term warming. Samples were collected from the Chukchi Sea off the coast of Barrow, Alaska, during winter, spring, and summer and incubated for 24h in the dark with additions of (NH4+)-N-15 at -1.5, 6, 13, and 20 degrees C. Rates of NH4+ uptake and nitrification were measured in conjunction with bacterial production. In all seasons, NH4+ uptake rates were highest at temperatures similar to current summertime conditions but dropped off with increased warming, indicative of psychrophilic (i.e., cold-loving) microbial communities. In contrast, nitrification rates were less sensitive to temperature and were higher in winter and spring compared to summer. These findings suggest that as the Arctic coastal ecosystem continues to warm, NH4+ assimilation may become increasingly important, relative to nitrification, although the magnitude of NH4+ assimilation would be still be lower than nitrification.
Inorganic Nitrogen Uptake; Nitrifying Bacteria; Oxidation-Kinetics; Solvent-Extraction; Oxidizing Bacteria; Microbial-Growth; Climate-Change; Polar Oceans; Fresh-Water; Archaea
Baer, SE; Connelly, TL; Sipler, RE; Yager, PL; and Bronk, DA, Effect of temperature on rates of ammonium uptake and nitrification in the western coastal Arctic during winter, spring, and summer (2014). Global Biogeochemical Cycles, 28(12), 1455-1466.