| Contributors | Affiliation | Role |
|---|---|---|
| Granger, Julie | University of Connecticut (UConn) | Principal Investigator |
| Bourbonnais, Annie | University of Massachusetts Dartmouth (UMass Dartmouth) | Co-Principal Investigator |
| Wilson, Samuel | University of Hawai'i (UH) | Co-Principal Investigator |
| Biddle, Mathew | Woods Hole Oceanographic Institution (WHOI BCO-DMO) | BCO-DMO Data Manager |
Comparison of MIMS to IRMS
We tested whether the mass-specific signal ratios returned by MIMS accurately quantitate the relative isotopic abundance of 15N2 in the range typically used for N2 fixation incubations. Incremental 15N2 gas aliquots were equilibrated in seawater, and respective solutions were then dispensed into replicate gas-tight vials. 15N atom % of dissolved N2 values were measured in parallel by continuous flow IRMS on a GV Isoprime IRMS (Charoenpong et al., 2014) and by MIMS (Bay Instruments), on the assumption that values returned by IRMS are accurate.
BCO-DMO Processing Notes:
- table was extracted from original spreadsheet.
- added conventional header with dataset name, PI name, version date
- modified parameter names to conform with BCO-DMO naming conventions
| File |
|---|
mims_2_irms.csv (Comma Separated Values (.csv), 465 bytes) MD5:7b8dbeb0ef6ce3be753fead18af7c9e9 Primary data file for dataset ID 778065 |
| Parameter | Description | Units |
| Subsample | subsample identification | unitless |
| MIMS_at_pcnt | MIMS at% | unitless |
| stdev_MIMS_at_pcnt | stdev MIMS at% | unitless |
| IRMS_15N_at_pcnt | IRMS 15N at% | unitless |
| stdev_IRMS_15N_at_pcnt | stdev IRMS 15N at% | unitless |
| IRMS_at_pcnt_no_furnace | IRMS at% no furnace | unitless |
| stdev_IRMS_at_pcnt_no_furnace | stdev IRMS at% no furnace | unitless |
| Dataset-specific Instrument Name | Isotope Ratio Mass Spectrometer |
| Generic Instrument Name | Isotope-ratio Mass Spectrometer |
| Dataset-specific Description | continuous flow Delta V Isotope Ratio Mass Spectrometer (Smith et al. 2015), and continuous flow-GV Isoprime IRMS (Charoenpong et al., 2014) |
| Generic Instrument Description | The Isotope-ratio Mass Spectrometer is a particular type of mass spectrometer used to measure the relative abundance of isotopes in a given sample (e.g. VG Prism II Isotope Ratio Mass-Spectrometer). |
| Dataset-specific Instrument Name | Membrane Inlet Mass Spectrometer |
| Generic Instrument Name | Membrane Inlet Mass Spectrometer |
| Dataset-specific Description | Membrane Inlet Mass Spectrometer (Bay Instruments) |
| Generic Instrument Description | Membrane-introduction mass spectrometry (MIMS) is a method of introducing analytes into the mass spectrometer's vacuum chamber via a semipermeable membrane. |
NSF Award Abstract:
The availability of nitrogen is required to support the growth and production of organisms living in the surface of our global ocean. This element can be scarce. To alleviate this scarcity, a special class of bacteria and archaea, called nitrogen fixers, can derive the nitrogen needed for growth from nitrogen gas. This project would carefully examine one specific method for measuring nitrogen fixation that has been used recently to suggest the occurrence of small amounts of nitrogen fixation in subsurface ocean waters. If these reports are verified, then a revision of our understanding of the marine nitrogen cycle may be needed. The Ocean Carbon and Biogeochemistry program will be used as a platform to develop community consensus for best practices in nitrogen fixation measurements and detection of diversity, activity, and abundances of the organisms responsible. In addition, a session will be organized in a future national/international conference to communicate with the broader scientific community while developing these best practices.
The goal of this study is to conduct a thorough examination of potential experimental and analytical errors inherent to the 15N2-tracer nitrogen fixation method, in tandem with comprehensive molecular measurements, in mesopelagic ocean waters. Samples will be collected and experimental work conducted on a cruise transect in the North Atlantic Ocean, followed by analytical work in the laboratory. The specific aims of this study are to (1) determine the minimum quantifiable rates of 15N2 fixation based on incubations of mesopelagic waters via characterization of sources of experimental and analytical error, and (2) seek evidence of presence and expression of nitrogen fixation genes via comprehensive molecular approaches on corresponding samples. The range of detectable rates and diazotroph activity from the measurements made in this study will be informative for the understanding of the importance of nitrogen fixation in the oceanic nitrogen budget.
| Funding Source | Award |
|---|---|
| NSF Division of Ocean Sciences (NSF OCE) |