Sandia National Laboratories technologist Jenna Schambach working with a sample of Alaska lakebed soil. By studying the microbes in the soil, and the gases they emit, Schambach and project lead Chuck Smallwood hope to improve our understanding of the rapidly melting Arctic permafrost and improve computer models of climate change. Credit: Craig Fritz/Sandia National Laboratories
As rising global temperatures lead to thawing of Arctic permafrost, previously trapped greenhouse gasses such as carbon dioxide and methane are released into the atmosphere, potentially exacerbating climate change. Better technology is needed to study the Arctic soil-dwelling microbes that produce these gasses, and the impact these emissions will have on the climate, without the need for complicated and destructive permafrost soil sampling methods. Researchers from Sandia National Laboratories are now working on a project to understand the biological processes behind Arctic greenhouse gas emissions that could lead to better climate change models and the development of sensitive portable detectors for improved monitoring of gas production in the Arctic.
The Sandia researchers teamed up with the University of Alaska, Fairbanks to collect permafrost samples from two frozen lakes that were formed from thawing permafrost about 20 minutes north of Fairbanks, Alaska. They collected samples in March and September, and plan to collect additional samples from thawing coastal marshlands near Oliktok Point on the North Slope of Alaska next year. In order to collect soil samples from the lakebed, the researchers first cleared snow from the frozen lake surface and checked for signs of thin ice, then prepared the site by using a chainsaw to cut down through 3 to 4-foot-thick ice and remove large blocks from the surface. A hammer corer was then used to collect 3-foot-long samples of frozen lakebed soil, while a Vibracore sampler was used to collect samples up to 13 feet deep. The core samples, ranging in length from 3 to 10 feet, were frozen and shipped to New Mexico for extraction and study of microbes from the Arctic soil by Sandia scientists. The researchers also collected and measured greenhouse gas emissions from various field sites in the area, using small adsorption tubes to collect gas samples.
The team aims to use the microbe and gas samples to both understand how certain populations of bacteria and archaea produce greenhouse gasses under certain conditions, and how certain mixtures of gasses in emissions can serve as “biomarkers” for indirectly monitoring microbial gas production in the future. The researchers will grow microbes from the lakebed soil samples in temperature- and moisture-controlled bioreactors that can simulate the environment of the thawing-permafrost lake system, explained Sandia bioengineer and project lead Chuck Smallwood. They also plan to sequence the DNA from the samples to identify the types of microorganisms present in different layers of the lakebed, and use similar sequencing approaches to track how microbe populations change over time during temperature and nutrient changes. RNA sequencing will also be used to connect microbes with specific activities, such as to identify which microbes are chiefly responsible for methane production, or which microbes provide vitamins and other indirect assistance to the methane producers, said Smallwood.
The researchers are using comprehensive two-dimensional gas chromatography-mass spectrometry (GCxGC-MS) to analyze both the gas samples collected at field sites and gasses produced in real-time from microbes grown in the bioreactors. The use of a second column for separation in GCxGC will allow the researchers to better identify trace volatile compounds that may serve as markers for biological activity within the permafrost environment, said Sandia biological engineer Philip Miller, who is spearheading the gas analysis efforts. These insights can aid in the development of portable sensing technology that targets these biomarker compounds in order to monitor the rapidly changing microbial ecosystems of the thawing Arctic without the need for destructive sampling, said Smallwood. The group aims to develop this new monitoring technology by the end of the three-year research project.
“I feel like this type of research to define how living organisms and climate impact each other is really taking off. People are finally paying attention not just to what is happening above ground but how things are changing underneath our feet,” said Smallwood. “For a long time, scientists only viewed soils as a source of carbon, but now we’ve realized that soils can produce or remove greenhouse gases. We are working with computational modelers such as Umakant Mishra at Sandia to ultimately model how soil microbes are contributing to greenhouse gas emissions to reduce uncertainties in our climate change predictions.”
During their field expeditions, the researchers discovered unexpectedly high methane emissions at several sites, including at the lakebed bore hole site where methane concentrations were measured at 500-800 parts per million — roughly 400 times the normal atmospheric level of methane. The discovery of these methane “chimneys” hiding out in the Arctic demonstrates the importance of better understanding and monitoring microbial methane production in order to improve climate change models and predictions in the future, noted Smallwood.