| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | August 10, 2017 |
| Latest Amendment Date: | August 10, 2017 |
| Award Number: | 1736896 |
| 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: | August 15, 2017 |
| End Date: | July 31, 2022 (Estimated) |
| Total Intended Award Amount: | $440,188.00 |
| Total Awarded Amount to Date: | $440,188.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
3720 S FLOWER ST FL 3 LOS ANGELES CA US 90033 (213)740-7762 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
3651 Trousdale Pkwy, ZHS 117 Los Angeles CA US 90089-0740 |
| 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): | 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 goal of the international GEOTRACES program is to understand the distributions of many chemical elements and their isotopes in the oceans. The National Science Foundation is supporting a U.S. GEOTRACES sampling expedition in the Pacific Ocean 2018, from Alaska to Tahiti. This award will focus on measurement of the stable isotopes of iron (Fe), nickel (Ni), zinc (Zn), copper (Cu), and cadmium (Cd) in seawater, filtered particles, and atmospheric aerosol particles on this expedition. The trace metals Fe, Ni, Zn, Cu, and Cd strongly influence marine biogeochemistry and carbon cycling. Measurements of isotope ratios -- the relative abundance of different forms of the same chemical element -- provide insights not possible from concentration measurements alone. The investigators will use isotope data to learn more about the inputs and outputs of these elements to the ocean as well as the biological processes that influence their distributions within the oceans, leading to greater understanding of the role these metals play in oceanic carbon cycling. The award will also host an international inter-lab comparison exercise for Cd isotope ratios at low concentrations in seawater. The project will support an early career investigator, a postdoctoral researcher, and undergraduate and graduate students.
The investigators will measure delta-56Fe, delta-60Ni, delta-65Cu, delta-66Zn, and delta-114Cd at high spatial resolution along the U.S. GEOTRACES Pacific Meridional Transect (PMT). The resulting oceanic sections of all five isotope systems will enable them to distinguish between competing ideas about the controls on trace metal distributions. A wide variety of hypotheses about marine biogeochemical trace metal cycling, addressing topics of global importance will be explored and tested, including: 1) How do different sources, productivity and export regimes, coupled with overturning circulation, control the distribution of Fe, Ni, Zn, Cu and Cd and their isotopes in the Pacific? 2) Do oxygen minimum zones act as sinks for Cd, Zn, Cu and Ni, while acting as sources for Fe? and 3) What sources are most important for supplying Fe to the North Pacific Ocean? The PMT section crosses two high nutrient-low chlorophyll (HNLC) regions and two oligotrophic gyres, as well as transecting the oldest waters in the ocean, allowing the investigators to use high-resolution isotope datasets to investigate competing hypotheses about the effect of vertical, horizontal and in situ biogeochemical processes on the distribution of all five metals and their isotopes. Aerosol dust, volcanogenic and reducing margin sediments, and hydrothermal vents such as the East Pacific Rise have all been hypothesized as major contributors to the dissolved Fe cycle in the Pacific. Measurement of iron isotope signatures in aerosols and near to oceanic sources will enable the identification and quantification the importance of these different iron sources and processes in supplying iron to the iron-limited surface ocean, especially important for the two HNLC regions along the PMT section.
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.
Nickel and copper are important nutrients for algae which live in the oceans, where they are the base of the food chain for important fisheries, and where they help to draw down carbon dioxide. Just as humans require these important nutrients to be healthy, the microscopic photosynthetic algae which live in the oceans require small amounts of nickel and copper in order to survive. Humans obtain nickel, copper, and other nutrients from the food we eat, while algae in the oceans must obtain these nutrients from seawater. Therefore, it is important to understand how these metals get into seawater, and how they are distributed thorughout the global oceans.
The primary goal of this project was to measure nickel (Ni) and copper (Cu) in the North Pacific Ocean, using samples collected during the US GEOTRACES GP15 oceanographic cruise. Hundreds of seawater samples were collected during this cruise, at locations from the coast of Alaska, down past Hawaii, over the equator, and into the South Pacific near Tahiti, at depths ranging from the surface ocean down to near the ocean floor thousands of meters below. These samples were then returned to our laboratories, where we extracted Ni and Cu to measure both their concentrations in seawater, and their stable isotope ratios.The concentrations of Ni and Cu both decrease towards the surface ocean. This reflects the fact that phytoplankton in the surface ocean are taking these metals out of seawater to use as nutrients, then subsequently dying, and sinking into the deep ocean, taking their nickel and copper with them. By measuring exactly how much Ni and Cu concentrations decrease in the upper ocean, we can better understand how much is removed by phytoplankton. Metal stable isotope 'fingerprints' provide unique information about nickel and copper. Specifically, we find that there are more heavy nickel isotopes in the surface ocean than at depth, reflecting the fact that phytoplankton are preferentially removing the lighter isotopes of nickel. Additionally, we find that nickel isotopes are especially heavy in the South Pacific ocean near the equator, which suggests an especially high demand for Ni by phytoplankton living here, perhaps for the process of nitrogen fixation.
These data contribute to the global database of Ni and Cu concentrations and stable isotope ratios produced from the GEOTRACES program. By combining our data with other data from across the world, we will better understand how these important algal nutrients affect life in the oceans.
Last Modified: 01/10/2023
Modified by: Seth G John
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