Highlighting GRIIDC Researcher Dr. Jeff Chanton

Screen Shot 2020-08-06 at 1.12.55 PM.png

Photo by Dr. Jeff Chanton
Photo by Dr. Jeff Chanton

Dr. Jeff Chanton, acclaimed climate scientist and professor at Florida State University, has a built a lifelong career studying different geochemical processes in the Gulf of Mexico, peatlands, and landfills. A Gulf Coast native, he completed his undergraduate degree at New College of Florida in Sarasota, Florida, and went on to the University of North Carolina at Chapel Hill for his Master’s degree and Ph.D. where he focused on marine chemistry. His dissertation concentrated on sulfur cycling (and using stable S-isotopes) in anoxic marine sediments. Though he enjoyed his work with sulfur cycling and planned to continue in that direction, a new threat emerged in which he felt compelled to dive deeper. In the 1980s it was discovered that atmospheric methane concentrations were increasing rapidly, at an alarming rate of about 1 percent per year. Consequently, there was considerable interest in understanding why this was happening so he shifted his focus of study to methane and carbon cycling.

Gulf of Mexico Research Initiative
Chanton has been working with the Gulf of Mexico Research Initiative (GoMRI) since the initiation of the program following the Deepwater Horizon (DWH) oil spill in 2010. The DWH spill released around four million barrels of oil into the Gulf and as a result, and as part of the settlement with BP, the Gulf of Mexico Research Initiative was created as an independent research group tasked with studying the effects of the oil spill for the next ten years. Throughout the program, Chanton has worked with several consortia including C-IMAGE, ECOGIG, and DEEP-C.

GRIIDC and Data Sharing
Additionally, Chanton was on the GRIIDC Advisory Board when the program first started. He played a role in building the structure of GRIIDC, as well as offering advice on how to make GRIIDC as effective and easy to use as possible. With his lifelong career in science, he realized the importance of well-organized data and the ability for others to be able to use and share data. He recalled the past when one would have to request hard copies of data that could sometimes take weeks or months to obtain, if at all. He advised that it should be a system that is easy enough for seasoned scientists such as himself to navigate through, as well newer tech-savvy scientists. With Chanton’s input, as well as the board's, the GRIIDC development team has created a user-friendly system that makes data sharable and findable for all interested parties.

C-IMAGE Research
Chanton’s work with the Center for Integrated Modeling and Analysis of Gulf Ecosystems (C-IMAGE) has focused primarily on radiocarbon, or 14C, tracing, to map patterns of the deposition of oil-derived carbon on the seafloor. Plants and animals assimilate carbon-14 from carbon dioxide and organic matter throughout their lifetimes. When they die, they stop exchanging carbon with the biosphere and their carbon-14 content then starts to decrease at a rate determined by the law of radioactive decay (1). Chanton explained that the carbon that came out of the well head as oil and methane was “fossil” carbon, meaning that it had no 14C within it. 14C has a half-life of about 5,000 years and after 50,000 years, any organic matter that is older than that is free of 14C, so the oil-carbon that spewed out of the well was considerably different than the natural carbon in the Gulf of Mexico at that time. Natural carbon in the Gulf is fixed from recent photosynthesis or comes down via rivers. Therefore, the oil spill itself was a tracer experiment as the carbon it added was isotopically different from the natural carbon present in the Gulf.

Inverse Tracer Opportunity
The DWH oil spill was a unique opportunity, albeit an unfortunate one, to conduct an inverse tracer experiment. Chanton explained that there is an experimental lake area in Canada where one could conceivably get a permit to do experiments that usually would not be allowed. In a typical tracer experiment, one might, for example, “inject 14C into a lake and follow it through the food web. Such an experiment would allow an investigator to measure the rates and movement of carbon through the system from photosynthesis to zooplankton to ducks and geese, etc,” he explained. The DWH oil spill created a similar opportunity, but it was inverted since it added 14C-free organic matter, or fossil petroleum derived carbon (petrocarbon), to the Gulf. This allowed Chanton and his colleagues to follow and map that fossil carbon into sediments, sinking and suspended particulate organic carbon, and even oysters and other fauna across the northern Gulf.

What did they find?
On the seafloor, the sediments contained 14C-depleted organic material to the southwest of the Deepwater Horizon site — below the surface expression of the oil spill and underneath the deep-sea plume. To the east, there was less of an effect. From the 14C distribution on the seafloor, Chanton and his colleagues were able to determine that between 4-9 percent of oil (2) that was released from the spill ended up on the sea floor through the process dubbed Marine Oil Snow Sedimentation Flocculent Accumulation, or MOSSFA. The MOSSFA process is, “driven by aggregation of phytoplankton, microbes and the incorporation of oil.”(3) This process is linked to the binding properties of marine snow which promotes particle and oil-residue aggregation. Marine snow mostly consists of biological debris that originates in the top layers of the ocean and then drifts to the sea floor, and in the case of oil spills, marine snow can also carry oil-residues to the sea floor. The MOSSFA process was not well known prior to this oil spill event and Chanton’s research helped the scientific community better understand it. It was thought that oil-sedimentation occurred in the 1979 Ixtoc oil spill but about 30 years later the evidence was not apparent from bulk 14C measurements (4).

How will this help in the event of another oil spill?
Chanton explained that tracing where oil goes following a spill is important because it does not just stay on the surface. As observed, it is picked up by marine snow particles, and transported to the deep sea. The GoMRI consortium Aggregation and Degradation of Dispersants and Oil by Microbial Exopolymers (ADDOMEx) has worked on further investigations of the MOSSFA process with detailed, well constrained experimental work. Chanton’s work quantified the process of marine snow landing on the sea floor, but not how it formed.

ECOGIG Research
Chanton also worked with the consortium Ecosystem Impacts of Oil & Gas Inputs to the Gulf (ECOGIG). This work focused on collecting sinking particles near the spill site with sediment traps at around 1,160-1,660 meters deep (5,6). He collaborated with Dr. Uta Passow of the University of California Santa Barbara Marine Science Institute and Dr. Arne Diercks of the University of Southern Mississippi. Passow and Diercks deployed sediment traps in the northern Gulf and observed many properties of sinking particulates, among them, radiocarbon. Immediately after the oil spill, for about six months, there was more 14C depleted materials falling out of the water column, but the particulate flux recovered, taking about three years for it to reach a baseline, more modern 14C value. In other words, it took quite a while for the water column to cleanse itself (7). These investigators also hypothesized that the sinking particulate organic carbon (POC) would absorb trace constituents from the water column which existed at concentrations that were low enough to be very difficult to measure. This extensive work began in 2010 and the record continued until 2018.

Chanton and his collaborators continue to publish the results of their work. They are currently collaborating with the Bureau of Ocean Energy Management (BOEM) who is helping them understand and interpret some of the results from the deepest zones of the eastern Gulf.

Experience working with GRIIDC
As a one of the earliest members of the GRIIDC Advisory Board, Chanton said that GRIIDC has come a long way since the beginning of the program. He joked that his input back then was to challenge GRIIDC to make their processes simple enough that even he could understand it. Chanton also believes sharing data is a very good thing. He considers it particularly advantageous to publicly post data and emphasized that it is becoming more apparent how important it is to allow others to be able to build on other’s work. He reminisced on the difficulty to obtain data in the past. He said lots of useful data were not easily accessible and values how GRIIDC has made searching and downloading data such a simple process.

He also praised the GRIIDC team and said they are always friendly and supportive whenever he had issues or questions he deemed silly. He said that he has always been able to call one of the team members and appreciates how helpful they have been.
Dr. Jeff Chanton has worked with GoMRI and GRIIDC since the beginning of the ten-year program and GRIIDC is delighted to have had the opportunity to work with such a prominent scientist in his field. We wish Dr. Chanton good luck in his future work and we continue to encourage others to share their data with us!

References
1. Beta Analytic Testing Laboratory. How Does Carbon Dating Work, 2020. https://www.radiocarbon.com/about-carbon-dating.htm

2. Chanton, J; Zhao, T.; Rosenheim, B.; Joye, S. B.; Bosman, S.; Brunner, C.; Yeager, K.; Diercks, A.R., Hollander, D. 2015. Using natural abundance radiocarbon to trace the flux of petrocarbon to the seafloor following the Deepwater Horizon oil spill Environmental Science and Technology, 49, 847−854 es-2014-046524. doi. 10.1021/es5046524

3. Passow, U, Ziervogel, K, Asper, V and Diercks, A. 2012. Marine snow formation in the aftermath of the Deepwater Horizon oil spill in the Gulf of Mexico. Environ Res Lett 7(3): 11. DOI: https://doi.org/10.1088/1748-9326/7/3/035301

4. Bosman, S.H., P.T. Schwing, R.A. Larson, N.E. Wildermann, G.R. Brooks, I.C. Romero, J. Sánchez-Cabeza, A. C. Ruiz-Fernández, M. L. Machain-Castillo, A. Gracia, E. Escobar-Briones, S. A. Murawski, D.J. Hollander, J.P. Chanton. The southern Gulf of Mexico: A baseline radiocarbon isoscape of surface sediments and examination for evidence of a marine snow oil deposition residual 36 years after the IXTOC I well blowout. PLOS 1 14 Apr 2020, 15(4):e0231678 DOI: 10.1371/journal.pone.0231678

5. Chanton, JP, SL C. Giering, S Bosman, K Rogers, J. Sweet, V. Asper, A. R. Diericks, U. Passow. 2018. Isotopic composition of sinking particles: Oil effects, recovery and baselines in the Gulf of Mexico, 2010–2015. Elem Sci Anth, 6: 43. DOI: https://doi.org/10.1525/elementa.298

6. Yan, B., U. Passow, J. Chanton, E. Nöthig, V. Asper, J. Sweet, M. Pitiranggon, A. Diercks, D. Pak. 2016. Natural Marine Particles Mediated Sedimentation of Oil and Drilling Mud Components from the DWH spill, Proceedings of the National Academy of Science 113 (24) E3332-E3340; doi:10.1073/pnas.1513156113

7. Rogers, K. L., S. H. Bosman, S. Weber, J. P. Montoya, and J. P. Chanton. 2019. Sources of carbon to suspended particulate organic matter in the northern Gulf of Mexico. Elem Sci Anth, 7:51. DOI: https://doi.org/10.1525/elementa.389