Bioavailability of Arctic soils

The Arcitc is warming faster than most other regions, especially in the last few decades. This warming is of great concern because currently, permafrost in the north contains twice the amount of carbon in the atmosphere. While most of that carbon is currently sequestered in frozen soil, warming will make some of this carbon available for microbial degradation. Presently, it is not well understood how much of this carbon will be emitted to the atmosphere and in what form (CO₂ or CH₄) as most research to-date on has focused on flux measurements without studying the below ground processes responsible for fluxes.

Now as part of an NSF funded project, my research group is studying how the bioavailability of soil carbon changes with temperature today and may have been affected by the Holocene thermal maximum. Analysis of the isotopic composition of the microbial lipids can provide information on the pool of carbon that is undergoing degradation and what microbial metabolisms dominate. Understanding the flow of carbon through microbial systems will allow us to better predict the impact of thawing permafrost, and therefore provide more robust model estimates of future climate scenarios.

Unravelling biogeochemical processes in the cryosphere

Glaciers currently cover over 10% of Earth surface and changes in the reflectivity of ice sheets can significantly impact the global sea level. Today, glacial surfaces absorb significantly more incoming solar radiation than they did 15 years ago due to having darker surfaces. While combustion processes have been blamed for this change in albedo, new studies are revealing the importance of biology in darkening ice. Research in my group is exploring the relative contribution of biology and fossil fuel combustion towards the darkening of glacier surfaces. At present we are focusing on developing our techniques on mountain glaciers in Alaska before taking this work to the Greenland Ice Sheet. Establishing a relationship between the sources of carbon on glacier surfaces will enable more accurate predictions of future glacial loss in Earth System models, which is critical for policy makers as they brace for future sea-level rise. Additionally, this works helps us understand the extreme limits of life on Earth.

Biosignatures in extereme environments

Extreme environments on Earth provide a natural laboratory for understanding how life may exist elsewhere in the universe. While microbes are generally found everywhere on Earth, in cold and dry conditions, microbial activity greatly decreases. Microbes find refuge from the extreme environments beneath the surface of rocks, where they are sheltered from the wind but still receive enough light to photosynthesize. If there is life on Mars, it is likely beneath the surface. Previously Dr. Z has studied these rock dwelling organisms in the driest place on Earth (Atacama Desert)and the Canadian high Arctic. Future studies will continue in other polar regions.

Understanding environmental controls of hydrocarbon degradation

Society needs energy to function. Unfortunately, accidental oil spills are a consequence of sustaining our energy needs. Historically, a suite of indicator compounds was used to detection of spilled oil in coastal environments. However, recent work has shown that once in the environment, the chemical composition of oil is transformed, increasing the abundance of compounds not included in conventional analysis. Due to this chemical alteration, past research into the fate of spilled oil may have overlooked a significant fraction of oil-derived compounds. Over the past five years, we have learned a lot about the fate of oil in the environment from the blowout of the Deepwater Horizon in the Gulf of Mexico. Heavily oiled saltmarshes now contain little oil, while oil still accumulates on sandy beaches. In my lab we have been studying the oil accumulating on beaches to understand if chemical weathering changes the bioavailability of said oil.

Combusted carbon in the ocean

Combusted carbon is ubiquitous in the environment. Fossil fuel combustion powers our modern life and biomass fires regenerate forests or help cook food. Based on current emissions and the lack of known sinks for this type of carbon, we should be knee deep in black carbon. But we are not. Therefore, more work is needed to close the black carbon budget. Previously, Dr. Z's research focused on identifying a long hypothesized black carbon storage pool, in marine dissolved organic matter. Even though this highly recalcitrant material is only a small percentage of the organic matter pool, its presence can dramatically affect the apparent age of the entire dissolved organic matter pool. Using a compound specific radiocarbon mehtod, Dr. Z determined that the 14C of black carbon in sea water was ~20,000 14C years old. That is the oldest fraction of DOM yet identified in the ocean carbon cycle. Since the chemical structure of black carbon observed in riverine samples was distinct from the open ocean, these findings challenge the paradigm that aromatic carbon is unreactive. While research in the Z-lab transitioned away from black carbon many unresolved questions about black carbon cycling remain and it is a direction that the Z-lab would like to pursue in the future.