Babbin, Rothman, Bosak, and Woosley Awarded mTerra Catalyst Funding

Brandon Milardo | EAPS News
Tuesday, March 26, 2019

EAPS scientists forge new pathways in oceanic and atmospheric research.

In its first year of existence, the mTerra Catalyst Fund, established by EAPS visiting committee member Michael Mars, funded projects that looked to the past to help scientists understand the historical development of geologic and biologic systems in river networks and fill in gaps in the climate record of Canada's Northwest Territories. This year, three research projects conducted by EAPS faculty will explore the oceans and atmosphere to inform future work in climate science and the evolution of life on Earth. 

The mTerra Catalyst Fund kickstarts innovative "high risk" earth and climate science research. This seed funding allows EAPS researchers to forge new paths of research and explore important aspects of the earth and climate system that are underexplored.

The MIT Department in Earth, Atmospheric and Planetary Sciences (EAPS) projects selected for mTerra Catalyst support this year are: Doherty Assistant Professor in Ocean Utilization Andrew Babbin's "Quantifying denitrification isotope effects via genetic engineering", Professor of Geophysics Daniel Rothman and Associate Professor Tanja Bosak's "Autocatalytic oxygenation of Earth's atmosphere," and Principal Research Scientist Ryan Woosley's "Measuring ocean acidification in polar waters."

Babbin's research focuses on the marine nitrogen cycle, which is important for understanding how microorganisms acquire the resources they need to grow and divide. The nitrogen cycle is also intimately linked to the ocean’s carbon cycle, and helps scientists understand how carbon is pulled out of the atmosphere by microbes like phytoplankton and stored in the ocean’s depths. “The inventory of fixed, i.e. biologically available, nitrogen limits the productivity of much of the world's oceans, and in turn significantly feeds back on Earth's climate through its coupling to the carbon cycle,” says Babbin. So, it’s important to understand how nitrogen is depleted in the oxygen deficient regions of the eastern tropical Pacific Ocean, the Arabian Sea, and marine sediments.

However, quantifying the global marine nitrogen loss budget is difficult in the modern ocean, let alone given changing environmental conditions. For this reason, researchers make a number of assumptions to describe the marine nitrogen cycle and how it’s mediated by various ocean characteristics, like temperature and pH.

To fill in the scientific gaps, Babbin and EAPS graduate student Diana Dumit will investigate each of four metabolic reduction steps of heterotrophic dentrification, a process by which bioavailable nitrogen is consumed by the microbial conversion of nitrate to nitrite to nitric oxide to nitrous oxide and finally to dinitrogen. They will examine how a suite of genetically modified bacteria Pseudomonas aeruginosa, each incapable of performing three of the four steps of denitrification, is able to metabolize intermediate compounds in the pathway. The researchers will evaluate these products for isotopic abundances of nitrogen and oxygen for each isolated step. The differential processing of lighter and heavier isotopes in biological processes forms the root of many interpretations of how the oceans have functioned in both the modern and over history. They’ll repeat the experiments across a range of temperatures, pH levels, and oxygen saturation levels. In this way, they can probe the pathway in detail. Babbin’s research will also examine the often overlooked chemical intermediates critical for understanding anaerobic biogeochemistry that takes place in these regions.

He hopes that the results will aid scientists as they analyze the modern nitrogen budget and tease apart the geological record. Additionally, “by manipulating the temperature, oxygen, and pH, we can infer how nitrogen biogeochemistry is likely to change in the future as oceans warm, deoxygenate and acidify.”

While Babbin is looking at the marine system, Rothman and Bosak are focusing on the atmosphere over geological timescales. Joined by EAPS graduate student Haitao Shang, they are seeking to understand how oxygen accumulated in Earth’s atmosphere, which began around 3 billion years ago, and whether a similar increase can be expected on other planets. Processes like this have the potential to irreversibly alter biogeochemistry and evolution like on Earth.

To explain the rise, they propose that Earth’s oxygenation happened because the interactions between the environment and the biota were unstable: Shifts in biochemical processes occurred that promoted photosynthetic production of free oxygen. Subsequent changes in biogeochemical processes in marine sediments then led to enhanced preservation of organic carbon and the accumulation of atmospheric oxygen.

Rothman and Bosak will test this experimentally—looking at how two different autocatalytic mechanisms worked in Earth’s past—and theoretically—zeroing in on how these mechanisms could influence atmospheric oxygen levels.    

They want to be able to explain which environmental conditions can realistically lead to stable geological oxygen conditions, and point to environmental evidence. The results of their work could “revolutionize a field that has long implicitly assumed that biogeochemical cycles are permanently stable,” the researchers say.

While Rothman and Bosak concentrate on oxygen accumulation in the atmosphere, Woosley is looking at the effects of rising carbon dioxide levels in the Arctic Ocean. The Arctic is disproportionately experiencing the effects of climate change, warming at twice the rate of the rest of the world. Aside from accelerated warming, carbon dioxide gas is absorbed by the surface Arctic waters where it dissociates causing a decrease in pH, so measuring this is incredibly important. However, several factors make this difficult to understand: the remoteness and the harsh environment. But mostly, scientists don’t fully understand the limitations of equipment and how readings vary in cold temperatures. Additionally, the mathematical relationships (expressed as constants) between different components of the marine carbon system like alkalinity and total inorganic carbon -- which are well understood in warmer, saltier waters -- break down in cold conditions.

In order to bridge this knowledge gap, Woosley, along with two Undergraduate Research Opportunities Program (UROP) students, plan to conduct experiments in conditions similar to the Arctic in order to quantify the uncertainties and their causes in measuring ocean acidification. Focusing on the underlying chemistry, one area they will focus on is the reliability of dye that’s used to test pH. Others include evaluating how pH and different components of the carbon system shift with temperature, and how much error exists between the calculated carbon system components, which uses established mathematical relationships, and the direct measurements.

With mTerra Catalyst funding, Woosley’s group will provide direct and accurate measurements of carbon system at low temperatures. Their results will inform best practices for making oceanic pH measurements in regions like the Arctic and serve as a stepping stone to more complex experiments in the field. 

Support provided by the mTerra Catalyst Fund is an important first step for projects that might otherwise not be undertaken due to their speculative nature. But these projects have the potential to contribute crucial information to how we view and understand Earth systems. The scientists hope to parlay the findings into larger projects with more traditional sources of funding.

Michael Mars is pleased to see how his seed fund is working so far. “I established this seed fund to spark original research in the earth and climate sciences, and am delighted at the response by EAPS faculty and students. I look forward to hearing about their results and watching these projects take off.”

Story Image: Arctic Ocean swirls acquired by the European Space Agency's Envisat. (Credit: ESA – CC BY-SA IGO 3.0)