Anthony's Science Blog

Microbial communities in melting permafrost

December 14, 2011 – 4:23 pm

There is a cool new study in Nature about changes in the soil microbial community at the time of thaw. Using some cutting edge genomics-based approaches in which they sequenced massive amounts of DNA in frozen and unfrozen soil cores, the authors were able to show that:

…during transition from a frozen to a thawed state there are rapid shifts in many microbial, phylogenetic and functional gene abundances and pathways.

This past week at AGU, I was talking with some colleagues about microbial community composition during thaw. Some of the data from our Arctic project shows a rapid change in microbial C:N ratio combined with high nutrient levels in the soil solution around the time of thaw. My best explanation for those data is that there is a microbial turnover event in which lysed microbial cells release nutrients, which are subsequently taken up by new microbes. The great data that this team was able to generate seems consistent with that idea.

There were also some cool nitrogen-related findings like this:

Several genes involved in the N cycle shifted in abundance during thaw (Fig. 3c). For example, nitrate reductase I genes significantly increased, suggesting nitrate was available as a terminal electron acceptor, which was confirmed by its presence in the chemical data

Obviously these methods have a lot of potential for major advances in our understanding of soil ecology, which probably explains why there are so many departments seeking to add researchers familiar with these techniques to their faculty.

Although these findings don’t speak directly to the fate of permafrost carbon, it is becoming increasingly clear that there are huge changes in microbial function when soils thaw; the nature of those changes will likely dictate what happens to the stored C.