
NSF Org: |
OCE Division Of Ocean Sciences |
Recipient: |
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Initial Amendment Date: | February 25, 2011 |
Latest Amendment Date: | February 25, 2011 |
Award Number: | 1061876 |
Award Instrument: | Standard Grant |
Program Manager: |
David Garrison
OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
Start Date: | March 1, 2011 |
End Date: | February 28, 2014 (Estimated) |
Total Intended Award Amount: | $445,837.00 |
Total Awarded Amount to Date: | $445,837.00 |
Funds Obligated to Date: |
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History of Investigator: |
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Recipient Sponsored Research Office: |
66 GEORGE ST CHARLESTON SC US 29424-0001 (843)953-4973 |
Sponsor Congressional District: |
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Primary Place of Performance: |
66 GEORGE ST CHARLESTON SC US 29424-0001 |
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
Intellectual Merit: Despite the critical importance of viruses in shaping marine microbial ecosystems, very little is known about the molecular mechanisms mediating phytoplankton-virus interactions. As a consequence, we currently lack biomarkers to quantify active viral infection in the oceans, significantly hindering our understanding of its ecological and biogeochemical impacts. The coccolithophore Emiliania huxleyi (Prymnesiophyceae, Haptophyte) is a cosmopolitan unicellular photoautotroph whose calcite skeletons account for about a third of the total marine CaCO3 production. E. huxleyi forms massive annual spring blooms in the North Atlantic that are infected and terminated by lytic, giant double-stranded DNA containing coccolithoviruses. Findings that lytic viral infection of E. huxleyi recruits the hosts programmed cell death (PCD) machinery demonstrate that viruses employ a sophisticated, co-evolutionary ?arms race? in mediating host-virus interactions. The investigators recently demonstrated that viral glycosphingolipids (vGSLs), derived from unexpected cluster of sphingolipid biosynthetic genes, a pathway never before described in a viral genome, play a crucial functional role in facilitating infection of E. huxleyi. The observations of vGSLs in the North Atlantic and Norwegian fjords further suggest that they may be novel, diagnostic biomarkers for viral infection of coccolithophore populations. At the same time, the discovery of vGSLs and a distinct, protective 802 lipid argues that a host-virus, co evolutionary chemical arms race plays a pivotal role in regulating viral infection and in lubricating upper ocean biogeochemical fluxes of C and S.
The focus of this project is to elucidate the molecular, ecological, and biogeochemical links between vGSLs (and other polar lipids) and the global cycles of carbon and sulfur. The team of investigators proposes a multi-pronged approach combing a suite of lab-based, mechanistic studies using several haptophyte-virus model systems along with observational studies and manipulative field-based experiments the Northeast Atlantic. Using these diagnostic markers, they will document active viral infection of natural coccolithophore populations and couple it with a suite of oceanographic measurements in order to quantify how viral infection (via vGSLs) influences cell fate, the dissolved organic carbon (DOC) pool, vertical export of particular organic (POC) and inorganic carbon (PIC; as calcium carbonate, CaCO3) (along with associated alkenone lipid biomarkers and genetic signatures of viruses and their hosts) and the upper ocean sulfur cycle (via the cycling of dimethylsulfide [DMS] and other biogenic sulfur compounds). Furthermore, given they are unique to viruses, they propose that vGSLs can be used to trace the flow of virally-derived carbon and provide quantitative insights into a ?viral shunt? that diverts fixed carbon from higher trophic levels and the deep sea. The overarching hypothesis for this study is that vGSLs are cornerstone molecules in the upper ocean, which facilitate viral infection on massive scales and thereby mechanistically ?lubricate? the biogeochemical fluxes of C and S in the ocean.
Broader Impact: This research blends concepts in physiology, molecular biology, biochemistry, viriology and lipid chemistry, with oceanography and biogeochemistry, thereby providing an opportunity whereby researchers with different educational backgrounds can interact and develop. This project provides excellent hands-on training for development of postdocs, graduate students and undergraduate students. The research provides resources and opportunities for inter-institutional exchange Rutgers-WHOI-College of Charleston and builds both on established national and international collaborations and will foster new ones. The PIs will work with COSEE NOW and ?Networked Ocean World? to increase ocean literacy by integrating scientific research with K-12 educators and public audiences. An important component of this project is to bring scientists at sea in touch with classroom students and the general public. As such, the project incorporates several concrete strategies, including: (1) posting web/video blogs from sea; (2) incorporating a freelance videographer to collect multimedia content on a cruise to the Northeast Atlantic, which will be used in diverse post-cruise deliverables; (3) producing ?Ocean Gazing? podcasts so the general public can look at, listen to and touch the ocean and unpack some of its secrets by presenting ongoing oceanographic research and interviewing oceanographers; and (4) integrating the research activities with ongoing K-12 teacher workshops as part of the Marine Activities, Resources and Education program and through interactions with Laura Dunbar, a Science/Technology teacher at Sea Girt Elementary School (Sea Girt, NJ).
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.
Every spring in surface waters of theNortheast Atlantic Ocean, south of Iceland, a massive bloom of the unicellular coccolithophorid algae, Emiliania huxleyi can be seen from space using satellites. This algal bloom is an important component of the global carbon cycle since it removes carbon dioxide from the surface ocean waters due to both photosynthesis and calcification processes. Algal carbon fixed by these processes is then available for transport to the deep ocean. This export of carbon to the deep ocean allows more atmospheric carbon dioxide to move into surface waters of the ocean and thereby influence climate. Because of the impact of the carbon cycle on climate it is important to understand the factors that increase the growth rate, calcification rate and death of this organism. Our specific goal on this project was to identify and quantify the impact of viral infection on the physiology and ecology of Emiliania huxleyi during the spring and summer bloom period. A major field expedition entitled “North Atlantic Virus Infection of Coccolithophores Expedition (NA-VICE)” was completed in June/July 2012. Our science team boarded the RV Knorr at Ponta Delgado in the Azores on June 15, 2012 and then spent approximately 30 days collecting data and performing oceanographic experiments to study the importance of viruses on the carbon and sulfur cycles in Emiliania huxleyi.
Our specific objectives on the research cruise included measuring the community composition of algae in the water column, determining their growth and death rates and isolating various cells to make biochemical measurements of carbon and sulfur compounds that are important with respect to climate change. We determined using pigment analyses and microscopy that Emiliania huxleyi cells were the dominant algal population in surface waters. We measured doubling times of Emiliania huxleyi of approximately once per day and loss rates due to either predator grazing and/or by viral lysis of approximately one half that value. We measured photosynthetic and calcification rates as well as the amount of organic and inorganic carbon at various depths in the bloom areas. One major goal of our project was to determine the concentration of the climatically active trace gas, dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) within the algal cells. DMS in the atmosphere is oxidized tosulfate and ultimately is involved in cloud formation. Hence production of DMSP and DMS by marine coccolithophorids can influence the Earth’s heat budget since clouds are important in reflecting sunlight away from the Earth's surface. We isolated both healthy and virally infected coccolithophorid cells using a high speed flow cytometer at sea to determine the intracellular DMSP concentrations. Infected cells had significantly lower DMSP cell concentrations compared to healthy uninfected cells. Hence, it is possible that virally infected cells will contribute less DMS to the atmosphere compared to a healthy growing bloom.
The College of Charleston participants on the NA-VICE field expedition included one graduate (Jacob Kendrick) and one undergraduate student (Rachel Stevens). This expedition was the first research oceanographic experience for Ms. Rachel Stevens. Ms. Stevens performed the dilution experiments at sea to estimate growth and grazing rates and those data were used as part of her Bachelors Honors Thesis at the College of Charleston. Intracellular DMSP levels in virally infected and healthy Emiliania huxleyi populations served as part of the data leading to the completion of Mr. Jacob Kendrick’s Master’s Thesis in Marine Biology at the College of Charleston. Blogs from the cruise were posted and can be found online and educational videos are currently bein...
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