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Award Detail

Doing Business As Name:Rutgers University New Brunswick
  • John R Reinfelder
  • (848) 932-5737
Award Date:08/02/2016
Estimated Total Award Amount: $ 229,752
Funds Obligated to Date: $ 229,752
  • FY 2016=$229,752
Start Date:09/01/2016
End Date:08/31/2019
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:Collaborative Research: Transformations and mercury isotopic fractionation of methylmercury by marine phytoplankton
Federal Award ID Number:1634154
DUNS ID:001912864
Parent DUNS ID:001912864
Program:Chemical Oceanography
Program Officer:
  • Simone Metz
  • (703) 292-4964

Awardee Location

Street:33 Knightsbridge Road
Awardee Cong. District:06

Primary Place of Performance

Organization Name:Rutgers University New Brunswick
County:New Brunswick
Cong. District:06

Abstract at Time of Award

The accumulation of mercury (Hg) in seafood is a public health concern. The presence of Hg in seafood depends to a large degree on the air-sea exchange of Hg, with atmospheric deposition leading to accumulation of Hg in the ocean. The pathways to seafood start with the uptake of Hg by phytoplankton from seawater where is has always been assumed to accumulate to be eaten by grazers and passed on to larger organisms. This project challenges this assumption with preliminary data that suggests certain phytoplankton species can transform Hg to volatile forms (mercury vapor & dimethylmercury) that are lost to the atmosphere, a processes that removes Hg from the ocean rather than simply concentrating it into the ecosystem and seafood. This process, which has not been studied before, could dramatically alter our view of the Hg cycle in the ocean. The researchers funded by this project will look for the specific phytoplankton species that are capable of volatilizing Hg and quantify the rates at which they do so. They will also examine the suspected role of associated sulfur and selenium compounds in the process, as well as quantifying the changes in the Hg isotopic values for potential use as chemical tracers of the source of Hg in the ecosystem and food supply. These results should allow oceanographers to better quantify and refine our knowledge of Hg cycling in the ocean. The project will support participation of graduate students, a postdoctoral scientist, and incorporation of new information directly into courses taught by the researchers. Funding will also support continuing activities by the participants in activities that disseminate information on mercury and its effect on public and environmental health. Biogeochemical cycling of mercury (Hg) in the ocean may be more complex than previously assumed. New evidence has challenged the idea that methylmercury (MeHg) merely accumulates in phytoplankton and undergoes little to no transformation before being passed into the food web. This project aims to more fully elucidate the mechanisms behind the intracellular transformation of MeHg to volatile Hg and dimethylmercury (Me2Hg) that can be lost to the atmosphere, as well as to evaluate the range of algal taxa that can perform this transformation using directed culture work. Additionally, the PIs will investigate evidence that thiols, organic selenium (Se) compounds, and sulfides are required to facilitate these reactions within the phytoplankton, and specific pathways will be investigated and quantified through this research. Stable Hg isotopic data has been used to track Hg sources and pathways in marine systems and its fractionation during these MeHg transformations will also be quantified for future field study of marine Hg. The investigators hypothesize that coccolithophorids and other haptophytes capable of these intracellular reactions may account for a significant portion of the production of volatile Hg in the ocean. If this turns out to be the case, understanding and quantifying these volatilization processes may significantly alter our current understanding of the overall biogeochemical cycling of Hg in the ocean.

Publications Produced as a Result of this Research

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Kritee, K. and Motta, Laura C. and Blum, Joel D. and Tsui, Martin Tsz-Ki and Reinfelder, John R. "Photomicrobial Visible Light-Induced Magnetic Mass Independent Fractionation of Mercury in a Marine Microalga" ACS Earth and Space Chemistry, v., 2017, p.. doi:10.1021/acsearthspacechem.7b00056 Citation details  

Sontag, Philip T. and Steinberg, Deborah K. and Reinfelder, John R. "Patterns of total mercury and methylmercury bioaccumulation in Antarctic krill (Euphausia superba) along the West Antarctic Peninsula" None, v.688, 2019, p.. Citation details  

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.

Single-celled organisms known collectively as phytoplankton play an important role in the accumulation of the most toxic form of mercury, methylmercury, in aquatic food webs. Methylmercury is concentrated by phytoplankton from water by a factor of more than 10 thousand and cells enriched in methylmercury are consumed by zooplankton, a primary food source of larval, juvenile, and some adult fish. Indeed, nearly all of the methylmercury accumulated by fish is from their diet.  Sunlight drives the degradation of methylmercury in the ocean, but the effects of such photochemical processes on methylmercury inside phytoplankton cells in the sunlit upper layers of the ocean have not been studied.  In addition, photochemical transformations of mercury have been shown to selectively favor certain isotopes of mercury, producing reactant and product pools of mercury with measurably different isotope ratios.  The goals of this project were to 1) quantify the degradation of methylmercury inside phytoplankton cells exposed to sunlight and to 2) evaluate how such reactions affect the ratios of mercury stable isotopes in marine food webs.

In laboratory experiments with a species of marine phytoplankton that was originally isolated from the Irish Sea, we examined the accumulation and photochemical transformations of cellular methylmercury exposed to various wavelengths of light.  Our results showed that methylmercury inside phytoplankton cells was degraded upon exposure to both high energy ultraviolet light and moderate energy visible light. The results with visible light indicate that far more degradation of methylmercury occurs in the ocean than previously thought.  We also found that the ratios of mercury isotopes left behind in the phytoplankton followed similar patterns to what is observed in marine fish, including species consumed by humans.  This will allow us to better track how natural and pollution mercury enters marine food webs.

Last Modified: 12/29/2019
Modified by: John R Reinfelder

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