| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | December 8, 2016 |
| Latest Amendment Date: | December 8, 2016 |
| Award Number: | 1703664 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Michael Sieracki
OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | December 15, 2016 |
| End Date: | November 30, 2019 (Estimated) |
| Total Intended Award Amount: | $162,417.00 |
| Total Awarded Amount to Date: | $162,417.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
210 N 4TH ST FL 4 SAN JOSE CA US 95112-5569 (408)924-1400 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
8272 Moss Landing Road Moss Landing CA US 95039-9647 |
| 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 |
| 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
Carbon is fixed into organic matter by phytoplankton growing in the surface ocean, and is naturally sequestered in the ocean interior when particles and organisms sink: a process called the "biological pump." Because of its recognized influence on the global carbon cycle, ocean scientists have studied the biological pump for decades. However, we still do not have a sufficient understanding of the underlying processes to accurately quantify and predict carbon cycling. Much of this uncertainty stems from an inability to directly link specific plankton in the surface ocean with the types of particles sinking out of the surface ocean. To address this missing link in biological pump research, this work will directly observe how plankton are transported out of the surface ocean using novel, particle-specific observational approaches embedded within an interdisciplinary field program that will finely resolve upper ocean plankton groups and the resulting amount of sinking carbon across space and in time. The genetic identity of organisms within different types of sinking particles will be determined by sequencing the genetic contents of individually collected particles. This new application of a molecular method will definitively link surface plankton with sinking particles at five locations across the Pacific Ocean. This work has the potential to transform our understanding of the biological pump by identifying previously unknown links between surface ecosystems and sinking carbon particles. Because this work is embedded within an interdisciplinary field program, including biogeochemical modelers and remote sensing scientists, these data will feed directly into new models of the biological pump, improving our ability to quantify and predict carbon uptake by the ocean. This project will train 1 graduate student and at least 2 undergraduate researchers. Findings will be communicated to the non-scientific public through blogs, videos, and the public communication channels of participating institutions.
Accurate prediction of the global carbon cycle requires an understanding of the specific processes that link surface plankton communities and sinking particulate carbon flux (export) out of the surface ocean, but current methodological paradigms in biological pump research do not directly observe these processes. This project will comprehensively determine who is exported from the surface ocean and how using new, particle-resolving optical and molecular techniques embedded within a sampling scheme that characterizes export events at high time and space resolution. The investigation suggests that different plankton types in the surface waters are transported out of the surface ocean by distinct export pathways, and that an understanding of these connections is critical knowledge for global carbon cycle modeling. If successful, this work has the potential to transform our conceptual understanding of the biological pump by directly identifying mechanisms that link surface plankton with particle export, without relying on bulk sampling schemes and large-scale correlation analysis. Particle export environments will be studied at five open ocean locations during a cruise from Hawaii to Seattle in January-February 2017. The surface plankton communities will be characterized by a combination of satellite observations, sensors attached to a free-drifting, continuously profiling WireWalker, an in situ holographic camera, microscopy, and by sequencing 18S and 16S rRNA gene fragments. Exported particles will simultaneously be captured by various specialized sediment traps and their characteristics will be directly related to their sources in the surface community by identifying the genetic contents of individual particle types. Individual particles will be isolated from gel layers and the 16S and 18S rRNA gene fragments will be amplified and sequenced. This work would, for the first time, combine molecular approaches with particle-specific observations to enable simultaneous identification of both which organisms are exported and the processes responsible for their export.
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.
Right now, in all parts of the ocean, a rain of carbon-containing particles is sinking from the surface and into the deep ocean, effectively transporting carbon away from the atmosphere and sequestering it at depth. The amount of carbon transported by these "marine snow" particles is among the most poorly quantified components of the global carbon cycle and hinders the ability to accurately model current and future changes in the carbon cycle. The uncertainty is largely caused by the lack of data on the complex ecological interactions that eventually result in the vertical export of phytoplankton production. Specific members of the surface phytoplankton community are packaged into different sinking particle types. Each of these particle types contain different quantities of carbon, and differ in their tendencies to sink out of the surface and through the "twilight zone" depths of the ocean. To better quantify the ocean's carbon cycle, this project directly measured 1) which phytoplankton were packaged into specific particle types and 2) how much carbon each particle type exported from the surface ocean. Because these direct observations have traditionally been difficult to collect, we developed new analytical techniques that provide large quantities of biological data about individually-resolved particles. These techniques including sequencing the DNA contents of individually isolated particles, automated image processing of all sinking particle types, and machine learning classifiers to assign particles into ecological groups.
We observed these ecological mechanisms of carbon export during a research cruise that transited between Hawaii and Oregon in February-March 2017. At three location we deployed various instruments, including sediment traps that collected particles sinking 150 meters deep in the ocean. These sediment traps drifted freely from the ship for between 1 and 3 days before we recovered them once again and retrieved the particle samples. These samples included particles collected in a way that allowed us to measure the bulk quantity of organic carbon raining down and also to quantify and isolate individual particles. Particles that settled into a jar containing a viscous gel layer were imaged under the microscope and also individually extracted from the gel for DNA analysis.
We identified a shift in the ecological mechanisms of carbon export between locations in the subtropical ocean and the California Current. Particles sinking in the subtropical locations contained organisms typical of subtropical environments and most of the carbon was packed into aggregates and microzooplankton fecal pellets. In contrast, a larger percentage of the carbon sinking in the California Current was composed of crustaceous and gelatinous zooplankton fecal pellets. These pellets contained a different phytoplankton community than the cooccurring detrital aggregates, and were enriched in diatoms and green algae. The zooplankton in the California Current appear to have provided a distinct export mechanism for a specific subset of the surface phytoplankton community, especially the smallest phytoplankton cells. These data demonstrate how these particle-resolving optical and genetic approaches can generate the data needed to inform the next generation of ocean carbon models that are based on ecological mechanisms. The approaches that this project enabled us to develop are already being incorporated into other large-scale field campaigns (NASA EXPORTS) for the purposes of improving global carbon cycle models. In addition to these intellectual impacts, this work supported the interdisciplinary collaboration among oceanographers and a computer science student and also supported an early career PI. All data are publicly available in BCO-DMO and NCBI data repositories.
Last Modified: 03/24/2020
Modified by: Colleen A Durkin
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