
NSF Org: |
OCE Division Of Ocean Sciences |
Recipient: |
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Initial Amendment Date: | May 8, 2017 |
Latest Amendment Date: | May 8, 2017 |
Award Number: | 1733610 |
Award Instrument: | Standard Grant |
Program Manager: |
Henrietta Edmonds
hedmonds@nsf.gov (703)292-7427 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
Start Date: | May 15, 2017 |
End Date: | October 31, 2018 (Estimated) |
Total Intended Award Amount: | $49,900.00 |
Total Awarded Amount to Date: | $49,900.00 |
Funds Obligated to Date: |
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History of Investigator: |
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Recipient Sponsored Research Office: |
285 OLD WESTPORT RD NORTH DARTMOUTH MA US 02747-2356 (508)999-8953 |
Sponsor Congressional District: |
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Primary Place of Performance: |
285 Old Westport Road, Departmen North Dartmouth MA US 02747-2300 |
Primary Place of
Performance Congressional District: |
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Unique Entity Identifier (UEI): |
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Parent UEI: |
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NSF Program(s): |
BIOLOGICAL OCEANOGRAPHY, Chemical Oceanography |
Primary Program Source: |
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Program Reference Code(s): |
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Program Element Code(s): |
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Award Agency Code: | 4900 |
Fund Agency Code: | 4900 |
Assistance Listing Number(s): | 47.050 |
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.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Nitrogen is a key element in all organisms. In the ocean, the availability of nitrogen is often limiting the plankton primary production, but certain micro-organisms can alleviate this shortage by a biological mechanism: nitrogen (N2) fixation. The aim of this study was - through a variety of methods assessments - to investigate the importance of N2 fixation at depths below the sunlit surface layers of the ocean, and to elucidate the overall importance of N2 fixing microbes (diazotrophs) that are not cyanobacteria. A specific focus of this part of the collaborative project was to assess the community composition of these microbes in the water column by determining their relative abundances based on DNA sequencing, by assessing their gene expression activity, and by examining the abundances of the most prevalent community members with additional molecular quantification methods (quantitative Polymerase Chain Reaction). The project involved collection of samples in the North Atlantic Ocean water column, and bioinformatic analyses of these samples in the context of samples collected and analyzed from other ocean regions. The results show wide presence of putative diazotroph sequences from surface ocean extending to several hundred meters deep in the ocean where energy from sunlight does not penetrate. In this study, the deep communities appeared to generally exhibit low to non-detectable N2 fixation activity. The relative roles of the non-cyanobacterial groups potentially contributing to N2 fixation in the ocean appear to vary, with most apparently exhibiting a low N2 fixation activity. Yet, some of the non-cyanobacterial members of the microbial communities that are containing a key gene required for N2 fixation, show persistent depth-specific stratification both in surface (sunlit) and the deep (non-sunlit) layers, suggesting the distributions are not random but likely controlled by biological and/or chemical and physical factors.
Last Modified: 06/25/2019
Modified by: Pia Moisander
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