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Award Detail

Doing Business As Name:University of Georgia Research Foundation Inc
  • Brian Hopkinson
  • (706) 542-7880
Award Date:08/14/2010
Estimated Total Award Amount: $ 411,186
Funds Obligated to Date: $ 411,186
  • FY 2010=$411,186
Start Date:09/01/2010
End Date:08/31/2015
Transaction Type:Grant
Awarding Agency Code:4900
Funding Agency Code:4900
CFDA Number:47.074
Primary Program Source:040100 NSF RESEARCH & RELATED ACTIVIT
Award Title or Description:Collaborative Research: Ocean Acidification-Category 1: Effects of pCO2 and pH on Photosynthesis, Respiration and Growth in Marine Phytoplankton
Federal Award ID Number:1041034
DUNS ID:004315578
Program:CRI-Ocean Acidification

Awardee Location

Street:310 East Campus Rd
Awardee Cong. District:10

Primary Place of Performance

Organization Name:University of Georgia
Street:310 East Campus Rd
Cong. District:10

Abstract at Time of Award

Approximately one third of carbon dioxide emissions dissolve in the surface waters of the ocean and increase its acidity (the phenomenon of ocean acidification). Amongst the biological effects of seawater acidification are changes in the growth of phytoplankton, organisms that are the basis for marine food-webs. However, variable effects on phytoplankton growth of increasing carbon dioxide concentration have been reported, including an increase, no effect or a decrease. The objective of this project is to understand the physiological response of marine phytoplankton to increasing concentrations of carbon dioxide and acidity. This knowledge will make it possible to assess, and eventually predict, future changes in phytoplankton ecology and ocean productivity. The hypothesis to be tested is that the increase in carbon dioxide and the increase in acidity (a decrease in pH) both influence the growth of marine phytoplankton. It is postulated 1) that elevated carbon dioxide levels will lead to a higher photosynthetic efficiency, and 2) that a lower pH of seawater will decrease the energy that phytoplankton must spend to maintain their normal internal pH. Experiments will be carried out to test if differences in photosynthetic and respiratory physiology between phytoplankton species will result in different responses to carbon dioxide concentration and ocean acidity. These hypotheses will be tested in laboratory experiments and complementary field studies, using mass spectrometric techniques and the analysis of molecular markers to trace carbon and oxygen metabolism. Field experiments with natural phytoplankton will be carried out in New Jersey coastal waters, Bermuda, and iron-limited waters off California. Broader Impacts This project, which addresses an issue of significant concern to society, will provide research experiences for undergraduates and training for graduate students and a postdoctoral fellow. Summer interns from local junior colleges will participate in the project. A problem-based learning package on climate change and ocean acidification targeting middle and high school students and teachers will be developed. The principal investigators will work with Climate Central, a nonprofit organization that prepares media content for the web, television stations and other outlets that provide information to the public.

Publications Produced as a Result of this Research

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Losh, JL, FMM Morel, BM Hopkinson "Modest increase in the C:N ratio of N-limited phytoplankton in the California Current in response to high CO2" Marine Ecology Progress Series, v.468, 2012, p.31-42.

Shen C., Hopkinson B.M. "Size scaling of extracellular carbonic anhydrase activity in centric marine diatoms" Journal of Phycology, v.51, 2015, p.255.

Shi, D. Li, W. Hopkinson, B.M. Hong H. Li D. Kai S.J. Lin W "Interactive effects of light, nitrogen source, and carbon dioxide on energy metabolism in the diatom Thalaissiosira pseduonana" Limnology and Oceanography, v.60, 2015, p.1805.

Hopkinson, BM, C Meile, C Shen "Quantification of extracellular carbonic anhydrase in two marine diatoms and investigation of its role" Plant Physiology, v.162, 2013, p.1142-1152.

Hopkinson BM Young JN Tansik AL Binder BJ "The minimal CO2 concentrating mechanism of Prochlorococcus MED4 is effective and efficient" Plant Physiology, v.166, 2014, p.2205.

Oakley CA Schmidt GW Hopkinson BM "Thermal responses of Symbiodinium photosynthetic carbon assimilation" Coral Reefs, v.33, 2014, p.501. doi:10.1007/ss003380014-1130-9 

Oakley CA, BM Hopkinson, GW Schmidt "A modular system for the measurement of CO2 and O2 gas flux and photosynthetic electron transport in microalgae" Limnology and Oceanography Methods, v.10, 2012, p.968-977.

Hopkinson BM "A chloroplast pump model for the CO2 concentrating mechanism in the diatom Phaeodactylum tricornutum" Photosynthesis Research, v.121, 2014, p.223. doi:10.1007/s11120-013-9954-7 

Hopkinson, BM; Dupont, CL; Allen, AE; Morel, FMM "Efficiency of the CO2-concentrating mechanism of diatoms" PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, v.108, 2011, p.3830. doi:10.1073/pnas.101806210  View record at Web of Science

Marchetti A., Catlett D., Hopkinson B.M., Ellis K., Cassar N. "Marine diatom proteorhodopsins and their potential role in coping with low iron availability" ISME Journal, v.9, 2015, p.1751.

Kranz S.A., Young J.N., Hopkinson B.M., Goldman J.A.L. Tortell P.D., Morel F.M.M. "Low temperature reduces the energetic requirement for the CO2 concentrating mechanism in diatoms" New Phytologist, v.2015, 2015, p.192.

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.

Project Outcomes: Collaborative Research: Ocean Acidification Category 1: Effects of pCO2 and pH on Photosynthesis, Respiration, and Growth in Marine Phytoplankton

            As CO2 is released into the atmosphere through human activities a portion of this CO2 dissolves in the ocean, increasing the ocean’s CO2 concentration and lowering its pH. The chemical changes associated with increasing CO2 concentrations are known as ocean acidification and these chemical changes are expected to effect many organisms and ecosystems in the ocean. This project investigated the physiological effects of ocean acidification on marine phytoplankton, the unicellular microbes that are responsible for nearly all photosynthesis in the ocean. Our overarching goal of this collaborative project was to identify energetic savings due to alterations in photosynthesis or respiration that allow some phytoplankton to grow at more rapid rates when oceanic CO2 concentrations increase.

            The specific aim of the work carried out at the University of Georgia was to investigate the role of the CO2 concentrating mechanism (CCM) in mediating responses to ocean acidification. The CCM is a system used by microalgae to increase the concentration of CO2 around the photosynthetic enzyme responsible for carbon fixation, RubisCO, so that it is working rapidly and does not inadvertently react with O2 instead. In many algae, the CCM is dramatically down-regulated at high CO2. Energetic savings from decreased activity of the CCM is the most commonly offered explanation for increases in phytoplankton growth rates at high CO2, but exactly how much energy is saved, and hence whether this is a plausible explanation, was unclear. We intensively studied the CCMs in species that represent two key groups of marine phytoplankton: Phaeodactylum tricornutum, from the diatoms, a group of phytoplankton that dominates the community in highly productive regions, and Prochlorococcus marinus, from the picocyanobacteria, a group that dominates in low productivity regions of the ocean.

            We showed that the CCM of the diatom is driven by active transport of carbon from the cytoplasm into the chloroplast, building up a pool of carbon in the chloroplast to elevate CO2 around RubisCO and depleting inorganic carbon in the cytoplasm, which draws CO2 into the cell. This work combined physiological characterization of the CCM, using new ways to interpret isotopic tracers, and molecular identification of genes involved in the CCM. Through our better understanding of the CCM in this diatom, we accurately estimated that the down-regulation of the CCM should lead to energetic savings that will allow the diatom to grow 5-10% faster at CO2 concentrations predicted for year 2100. However, similar characterization of the CCM in the picocyanobacterium revealed that it was not down-regulated at predicted year 2100 CO2 concentrations because the CCM must raise the CO2 concentration around RubisCO to very high concentrations in cyanobacteria. Consistent with this finding, the growth rate of Prochlorococcus marinus, did not increase a...

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