Using stable isotopes and gas concentrations for independent constraints on microbial methane oxidation at Arctic Ocean temperatures


Contact
Christiane.Uhlig [ at ] awi.de

Abstract

Microbial oxidation of methane in oxic water bodies is an important control on the amount of dissolved methane which is released from the ocean to the atmosphere. We explored the use of stable isotope methane spikes to quantify methane oxidation rates in Arctic seawater samples. A Picarro G2201-i cavity ring-down spectrometer was used to determine methane concentration and isotope ratios from headspace samples in foil incubators. The methane mass balance and the change in stable isotope ratios served as independent constraints on methane oxidation. For a fractionation factor of 1.025 oxidation rate constants determined with both methods agreed within 20% for small changes in isotope ratio (e.g., 10‰). For large changes in isotope ratio (e.g., 90‰), which was outside the calibration range, methods diverged. Rate constants down to 0.01 / d could be resolved with high statistical support. Stable isotope infrared spectroscopy to determine methane oxidation in foil incubators (ISMOFI) was successfully tested on under ice seawater from Utqiagvik, Alaska, by repeated sampling from each incubation vessel. Depending on the amount of isotope spike added, we determined oxidation rates of 0.15 ± 0.02 nmol / (L*d) at in situ methane concentration and a maximal oxidation potential of 271 ± 41 nmol / (L*d). The ISMOFI method permits variable incubation durations from days to months in a single incubator. The method is transportable and applicable in a variety of field or seagoing laboratory environments, and it avoids the use of hazardous substances such as radioisotopes and toxic chemicals.



Item Type
Article
Authors
Divisions
Primary Division
Programs
Primary Topic
Peer revision
ISI/Scopus peer-reviewed
Publication Status
Published
Eprint ID
45456
DOI 10.1002/lom3.10199

Cite as
Uhlig, C. and Loose, B. (2017): Using stable isotopes and gas concentrations for independent constraints on microbial methane oxidation at Arctic Ocean temperatures , Limnology & Oceanography: Methods . doi: 10.1002/lom3.10199


Download
[img]
Preview
PDF
Uhlig_et_al-2017-Limnology_and_Oceanography__Methods.pdf

Download (603kB) | Preview
Cite this document as:

Share


Citation

Research Platforms
N/A

Campaigns


Actions
Edit Item Edit Item