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Award Detail

Doing Business As Name:Princeton University
  • Daniel M Sigman
  • (609) 258-2194
Award Date:03/28/2011
Estimated Total Award Amount: $ 619,900
Funds Obligated to Date: $ 619,900
  • FY 2011=$619,900
Start Date:04/01/2011
End Date:03/31/2016
Transaction Type:Grant
Awarding Agency Code:4900
Funding Agency Code:4900
CFDA Number:47.050
Primary Program Source:040100 NSF RESEARCH & RELATED ACTIVIT
Award Title or Description:Understanding the nitrogen isotopes of planktonic foraminifera: A modern Sargasso Sea study
Federal Award ID Number:1060947
DUNS ID:002484665
Parent DUNS ID:002484665
Program:Chemical Oceanography
Program Officer:
  • Henrietta Edmonds
  • (703) 292-7427

Awardee Location

Street:Off. of Research & Proj. Admin.
Awardee Cong. District:12

Primary Place of Performance

Organization Name:Princeton University
Street:Off. of Research & Proj. Admin.
Cong. District:12

Abstract at Time of Award

Nitrogen (N) and phosphorus are the two nutrients required in large quantity by phytoplankton in the ocean, and together they limit productivity throughout most of the tropical, subtropical, and temperate ocean. Both the cycling of N and its input/output budget have been argued to control the fertility of the ocean and the ocean's role in setting atmospheric CO2. The CaCO3 tests of foraminifera can represent a substantial fraction of marine sediments and have been used extensively in paleoceanography; they are an obvious target for isotopic analysis of microfossil-bound organic matter. In recent years, researchers at Princeton have developed a protocol for the isotopic analysis of foraminiferal shell-bound N. The current protocol is at least 100 times more sensitive than typical on-line combustion, allowing for rapid progress with a N isotope archive that was previously not feasible to measure. Measurements on surface sediments and a downcore record from the Caribbean show the promise of foraminifera-bound del15N (fb-del15N) to provide both a robust N isotope archive for paleoceanography, and one with a unique potential of richness, given the existence of multiple foraminiferal species with different depth habitats and behaviors. Moreover, the finding from the Caribbean Sea record -- reduced N fixation in ice age Atlantic -- has changed the scientific conversation about the nature of the input/output budget of oceanic fixed N and its potential to change ocean fertility and atmospheric CO2. However, the controls on fb-del15N have not yet been adequately studied. In this project, as a first major step in developing a foundation for the paleoceanographic application of fb-del15N, the same Princeton University team will study its genesis in the water column, transport to the seafloor, and early diagenesis. They will undertake this study in the Sargasso Sea south of Bermuda. This is one of the best studied regions of the ocean, in general and with respect to foraminifera, and a region that has been has been a focus of the N isotope research of the PI for the last decade and others previously. Moreover, its significant seasonality -- in physical oceanography, biogeochemistry, and foraminiferal species abundance -- will facilitate the effort to understand the controls on fb-del15N at a mechanistic level. The research team will participate in six Bermuda Atlantic Time-series Study (BATS) cruises over two years, collecting foraminifera and other N forms likely to provide insight into the controls on fb-del15N. From the nearby Oceanic Flux Program (OFP) moored sediment traps and from shallow sediments collected in the region, they will pick foraminifera shells and again make relevant ancillary measurements. This work will establish the relationship of foraminiferal biomass to shell-bound del15N for different species, and comparison of the foraminiferal isotope data with the upper ocean N pools will yield empirical isotopic relationships and work toward a mechanistic insight of fb-del15N (e.g., the importance of different N pools to the diets of different foraminifera; the role of algal symbionts). The sediment trap and surface sediment data will support the plankton tow data by integrating over longer time scales and will also address questions regarding late stage (e.g., gametogenic) calcification and the early diagenesis of fb-del15N and fb-N content. Broader Impacts: This study will yield an improved understanding of the nutrient dynamics of foraminifera, a class of organisms whose shells are a central tool in micropaleontology and paleoclimatology. The project will also build on the principal investigator's involvement in the Bermuda Institute of Ocean Sciences as an asset for integrating ocean-related education and research at both the undergraduate and graduate levels.

Publications Produced as a Result of this Research

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Wang, X. T., M. G. Prokopenko, D. M. Sigman, J. F. Adkins, L. F. Robinson, H. Ren, S. Oleynik, B. Williams, G. H. Haug "Isotopic composition of carbonate-bound organic nitrogen in deep-sea scleractinian corals: A new window into past biogeochemical change" Earth and Planetary Science Letters, v.400, 2014, p.. doi:10.1016/j.epsl.2014.05.048 

Treibergs, Lija A and Fawcett, Sarah E and Lomas, Michael W and Sigman, Daniel M "{Nitrogen isotopic response of prokaryotic and eukaryotic phytoplankton to nitrate availability in Sargasso Sea surface waters}" Limnology And Oceanography, v.59, 2014, p.972--985. doi:10.4319/lo.2014.59.3.0972 

Wang, X T and Sigman, D M and Cohen, A L and Sinclair, D J "{Isotopic composition of skeleton-bound organic nitrogen in reef-building symbiotic corals: a new method and proxy evaluation at Bermuda}" {\ldots} et Cosmochimica Acta, v., 2015, p.. doi:10.1016/j.gca.2014.09.017 

Fawcett, S E and Lomas, M W and Ward, B B "{The counterintuitive effect of summer-to-fall mixed layer deepening on eukaryotic new production in the Sargasso Sea}" Global {\ldots}, v., 2014, p.. doi:10.1002/(ISSN)1944-9224 

Erler, D V and Wang, X T and Sigman, D M and Scheffers, S R "{Controls on the nitrogen isotopic composition of shallow water corals across a tropical reef flat transect}" Coral Reefs, v., 2015, p.. doi:10.1007/s00338-014-1215-5 

Straub, Marietta and Sigman, Daniel M and Ren, Haojia and Mart{\'\i}nez-Garcia, Alfredo and Meckler, A Nele and Hain, Mathis P and Haug, Gerald H "{Changes in North Atlantic nitrogen fixation controlled by ocean circulation}" Nature, v.501, 2013, p.200--203. doi:10.1038/nature12397 

Erler, D. V., X. T. Wang, D. M. Sigman, S. R. Scheffers, B.O. Shepherd "Controls on the nitrogen isotopic composition of shallow water corals across a tropical reef flat transect" Coral Reefs, v., 2014, p.. doi:10.1007/s00338-014-1215-5 

Meckler, A N and Sigman, D M and Gibson, K A and Francois, R and Martinez-Garcia, A. and Jaccard, S L and R{\"o}hl, U and Peterson, L C and Tiedemann, R and Haug, G H "{Deglacial pulses of deep-ocean silicate into the subtropical North Atlantic Ocean}" Nature, v.495, 2013, p.495--498. doi:10.1038/nature12006 

Costa, K M and Mcmanus, J F and Anderson, R F and Ren, H and Sigman, D M and Winckler, G. and Fleisher, M. Q. and Marcantonio, F. and Ravelo, A. C. "{No iron fertilization in the equatorial Pacific Ocean during the last ice age}" Nature, v., 2016, p.1--16. doi:10.1038/nature16453 

Ren, Haojia and Brunelle, Brigitte G and Sigman, Daniel M and Robinson, Rebecca S "{Marine Chemistry}" Marine Chemistry, v.155, 2013, p.92--101. doi:10.1016/j.marchem.2013.05.016 

Fawcett, Sarah E and Ward, Bess B and Lomas, Michael W and Sigman, Daniel M "{Vertical decoupling of nitrate assimilation and nitrification in the Sargasso Sea}" Deep-Sea Research Part I, v.103, 2015, p.64--72. doi:10.1016/j.dsr.2015.05.004 

Wang, Xingchen T and Sigman, Daniel M and Cohen, Anne L and Sinclair, Daniel J and Sherrell, Robert M and Cobb, Kim M and Erler, Dirk V and Stolarski, Jaros{\l}aw and Kitahara, Marcelo V and Ren, Haojia "{Influence of open ocean nitrogen supply on the skeletal $\delta$15N of modern shallow-water scleractinian corals}" Earth And Planetary Science Letters, v.441, 2016, p.125--132. doi:0.1016/j.epsl.2016.02.032 

Wang, X. T., D. M. Sigman, A. L. Cohen, H. Ren, D. J. Sinclair, R. M. Sherrell, M. A. Weigand, D. V. Erler, H. Ren "Isotopic composition of skeleton-bound organic nitrogen in reef-building symbiotic corals: a new method and proxy evaluation at Bermuda" Geochemica et Cosmochimica Acta, v.148, 2014, p.. doi:10.1016/j.gca.2014.09.017 

Rafter, P A and DiFiore, P. J. "{Coupled nitrate nitrogen and oxygen isotopes and organic matter remineralization in the Southern and Pacific Oceans}" Journal of Geophysical {\ldots}, v., 2013, p.. doi:10.1002/jgrc.20316 

Ren, Haojia and Studer, Anja S and Serno, Sascha and Sigman, Daniel M and Winckler, Gisela and Anderson, Robert F and Oleynik, Sergey and Gersonde, Rainer and Haug, Gerald H "{Glacial-to-interglacial changes in nitrate supply and consumption in the subarctic North Pacific from microfossil-bound N isotopes at two trophic levels}" Paleoceanography, v.0, 2015, p.1--16. doi:10.1002/2014PA002765 

Altieri, Katye E and Fawcett, Sarah E and Peters, Andrew J and Sigman, Daniel M and Hastings, Meredith G "{Marine biogenic source of atmospheric organic nitrogen in the subtropical North Atlantic}" Proceedings of the National Academy of Sciences, v.113, 2016, p.925--930. doi:10.1073/pnas.1516847113 

Rafter, Patrick A and Sigman, Daniel M "{Spatial distribution and temporal variation of nitrate nitrogen and oxygen isotopes in the upper equatorial Pacific Ocean}" Limnology And Oceanography, v.61, 2015, p.14--31. doi:10.1002/lno.10152 

Treibergs, L. A., S. E. Fawcett, M. W. Lomas, D. M. Sigman "Nitrogen isotopic response of prokaryotic and eukaryotic phytoplankton to nitrate availability in Sargasso Sea surface waters" Limnology and Oceanography, v.59, 2014, p.. doi:10.4319/lo.2014.59.3.0972 

Martinez-Garcia, A. and Sigman, D M and Ren, H and Anderson, R F and Straub, M and Hodell, D A and Jaccard, S L and Eglinton, T I and Haug, G H "{Iron Fertilization of the Subantarctic Ocean During the Last Ice Age}" Science, v.343, 2014, p.1347--135. doi:10.1126/science.1246848 

Erler, Dirk V and Wang, Xingchen T and Sigman, Daniel M and Scheffers, Sander R and Mart{\'\i}nez-Garcia, Alfredo and Haug, Gerald H "{Nitrogen isotopic composition of organic matter from a 168 year-old coral skeleton: Implications for coastal nutrient cycling in the Great Barrier Reef Lagoon}" Earth And Planetary Science Letters, v.434, 2016, p.161--170. doi:10.1016/j.epsl.2015.11.023 

Straub, M and Tremblay, M M and Sigman, D M and Studer, A S and Ren, H and Toggweiler, J R and Haug, G H "{Nutrient conditions in the subpolar North Atlantic during the last glacial period reconstructed from foraminifera-bound nitrogen isotopes}" Paleoceanography, v.28, 2013, p.79--90. doi:10.1002/palo.20013 

Project Outcomes Report


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.

In order for us to understand how climate and the environment may change into the future, observing changes from year to year will simply not provide enough information. Year-to-year variations are typically minor and affected by random chance. If we seek to understand how climate and the environment behave on a meaningful time scale, we must observe them over at least many decades, probably centuries, as these are the shortest times over which conditions change significantly. The problem is that we only recently starting measuring the global environment, and we will not accumulate enough data if we just collect it one year after the next. Instead, scientists have to find ways to reconstruct changes before the time that measurements were being made. This usually involves a natural property that can be measured in material from a natural record such as a sediment or glacial ice core. We often refer to this measurable natural property as an environmental or climate “proxy,” signifying that it provides a replacement (albeit an imperfect one) for direct instrumental measurements of the environment.

The purpose of this project was to provide background information on a new “proxy” that the principle investigator’s research group recently developed for reconstructing nutrient conditions in the ocean. Nutrients are chemicals required for the growth of plankton, and their availability often controls the biological productivity of the ocean. This biological productivity can affect natural resources such as fisheries and can also affect climate by changing the concentration of the greenhouse gases (most importantly, carbon dioxide) in the atmosphere. The proxy being studied is the ratio of stable nitrogen isotopes of the organic matter trapped in the fossil shells of single-celled protist zooplankton called “foraminifera.” It took decades to develop the ability to make this measurement, in part because there is so little organic matter in the fossil shells. With the ability to make the measurement in hand, the NSF-funded project produced data to test the proxy’s ability to reconstruct nutrient conditions by studying the proxy in the modern ocean and in the fossils of recently deposited sediments that should reflect modern conditions.

Most of the study was conducted in the North Atlantic near Bermuda, taking advantage of the Bermuda Atlantic Time-series Study (BATS), a site in the open ocean visited by a ship every month to monitor conditions. Living foraminifera were collected with a net towed behind the ship, and the resulting samples were preserved and sent back to the lab for isotopic analysis. Many other types of dissolved and solid samples were collected at the same time and also analyzed. Analysis of these samples along with the information routinely collected by BATS provided information on the nutrient conditions that the foraminifera are believed to record. Foraminifera were also recovered from deep “sediment traps” that collect particles sinking out of the surface ocean as well as from the seafloor sediments where the fossils naturally accumulate. Comparison of the foraminifera measurements with the environmental data provided a test of the foraminifera nitrogen isotope proxy.

The results indicate that the foraminifera shells reflect the nitrogen of the organism’s biomass, a critical requirement if this tool is to be reliable. The isotopic differences among foraminifera species were shown to be relatively constant through time and similar in the surface ocean, sinking material, and the sediments. The nitrogen isotope ratio of individual foraminifera species showed signs of tracking the very subtle seasonal variation in the phytoplankton nitrogen isotopes at BATS, providing unexpected evidence that the proxy can be very precise. Moreover, there was no significant change in the for...

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