This summer, my advisor, Nicolas Cassar, and I are traveling to Arctic and sub-Arctic environments in Norway, Iceland, Greenland, Canada and Alaska to investigate how climate change is affecting nitrogen cycling and carbon sequestration.
Through polar amplification, the Arctic is warming up to four times faster than the global average, destabilizing the delicate nutrient balance of these ecosystems. Arctic warming and nutrient imbalance echo throughout the atmosphere and biosphere, with Arctic climate disruption exerting consequences on a global scale. Predictions of future atmospheric CO2concentrations assume that increases in carbon sequestration by primary production partially will offset increasing atmospheric CO2. However, nitrogen availability frequently limits photosynthesis in the Arctic. This means carbon sequestration depends in part on the amount of available nitrogen for photosynthesis, which in the Arctic primarily derives from biological nitrogen fixation (BNF) by bacteria and archaea (diazotrophs) associated with cryptogams (lichens and bryophytes). Despite the reliance of photosynthesis on nitrogen availability, the rate and magnitude of cryptogam-derived BNF are poorly constrained in the Arctic, impeding our ability to predict the climatic stability and future of global environments.
We plan to collect Arctic and sub-Arctic cryptogam and soil samples to measure the BNF activity of the diazotrophs in these samples in our lab at Duke. To do this, we will use an instrument developed in our lab called ARACAS. Compared to traditional acetylene reduction assay methods, ARACAS has 1000 times the sensitivity and a higher temporal resolution that allows continuous BNF measurements with time intervals on the order of seconds as opposed to hours or days. Through a series of experiments, we will simulate the ongoing shifts in temperature, moisture and nutrient levels due to climate change and use ARACAS to measure how the diazotrophs respond to different environmental conditions. It is a great privilege to conduct research in Arctic tundra environments, and we hope to return next year to measure BNF in situ with ARACAS.
We are excited to start our fieldwork this July at NERC Arctic Research Station and to continue our work in August at the Greenland Institute of Natural Resources. We hope you will join us throughout our journey by following our blog “Arctic Greening: Does Nitrogen Hold The Key?”