Metagenomic Insights into Decadal Changes in Carbon and Nitrogen Cycling in Arctic Tundra Biomes

Authors

Neslihan Tas1,2* (ntas@lbl.gov), Nancy Conejo1, Sarah Feng1, Marla DeKlotz1, Hoi-Ying Holman3, Colleen Iversen2

Institutions

1Earth and Environmental Sciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA; 2Climate Change Science Institute, Environmental Science Division, Oak Ridge National Laboratory, Oak Ridge, TN; 3Biosciences Area, Lawrence Berkeley National Laboratory, Berkeley, CA

URLs

Abstract

This project uses state of the art sequencing and imaging technologies to resolve complex interactions governing the biochemical cycles in tundra biomes to better inform efforts to decipher arctic carbon (C) and nitrogen cycling. Arctic soils are among the largest terrestrial C stores in the world, making them a critical focus for climate change research. However, rising global temperatures could cause rapid microbial mineralization and increased greenhouse gas (GHG) emissions from these C stores. Various landscape features, including soil surface and subsurface slope, redox gradients, ice wedge formation, and permafrost depth, create diverse microbial habitats that may respond differently to warming and perturbations. The seasonal changes in soil microbiomes and their impact on GHG production potential remain poorly understood.

Between 2011 and 2022, researchers conducted multiple sampling campaigns to collect active layer soils from the polygonal arctic tundra at the Barrow Environmental Observatory (BEO). The team analyzed the chemical and biological properties of these soils and monitored greenhouse gas (GHG) emissions. To better understand the microbial communities in these soils, researchers extracted and sequenced the whole community DNA, resulting in several hundred metagenome-assembled genomes (MAGs) and viral genomes (vMAGs). In addition, the team analyzed the soil biochemistry to better understand the relationship between soil properties and microbial communities via synchrotron Fourier transform infrared (SR-FTIR) spectral imaging at the Berkeley Infrared Structural Biology beamline of the Advanced Light Source (LBNL).

At the study location, the microbiomes of the tundra are organized according to topographical features, which has a direct impact on the distribution of key genes responsible for greenhouse gas (GHG) emissions. Researchers found that the potential for GHG production was localized and varied greatly between different polygons. The analysis of microbial genomes revealed that they have an improved resilience to changes in C availability, fluctuating temperatures, and nutrient-deficient conditions in tundra soils. While microbial communities did exhibit seasonal variations, landscape topography remained the main factor distinguishing the distribution of microbial functions over a thaw season. Integrating microbial functions with geochemistry and GHG fluxes enhances the understanding of how landscape topography shapes biogeochemical cycles in Arctic soils. This approach can help better predict the ecosystem responses to climate change and reduce uncertainties in future projections.