Award Abstract # 1733610
EAGER: Collaborative Research: Detection limit in marine nitrogen fixation measurements - Constraints of rates from the mesopelagic ocean

NSF Org: OCE
Division Of Ocean Sciences
Recipient: UNIVERSITY OF MASSACHUSETTS DARTMOUTH
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: FY 2017 = $49,900.00
History of Investigator:
  • Pia Moisander (Principal Investigator)
    pmoisander@umassd.edu
Recipient Sponsored Research Office: University of Massachusetts, Dartmouth
285 OLD WESTPORT RD
NORTH DARTMOUTH
MA  US  02747-2356
(508)999-8953
Sponsor Congressional District: 09
Primary Place of Performance: University of Massachusetts Dartmouth
285 Old Westport Road, Departmen
North Dartmouth
MA  US  02747-2300
Primary Place of Performance
Congressional District:
09
Unique Entity Identifier (UEI): PMMKPCKNN9R2
Parent UEI:
NSF Program(s): BIOLOGICAL OCEANOGRAPHY,
Chemical Oceanography
Primary Program Source: 01001718DB NSF RESEARCH & RELATED ACTIVIT
Program Reference Code(s): 4444, 7916, 8242
Program Element Code(s): 165000, 167000
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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Moisander, Pia H. and Benavides, Mar E. and Bonnet, Sophie and Berman-Frank, Ilana and White, Angelicque and Riemann, Lasse "Chasing after Non-cyanobacterial Nitrogen Fixation in Marine Pelagic Environments" Frontiers in Microbiology , v.8 , 2017 10.3389/fmicb.2017.01736 Citation Details

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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