A year in the active layer of Svalbard permafrost soil Small seasonal variation in the bacterial community in the active layer of Svalbard permafrost soil. svalbard_2010_2011

Active layer soil overlaying permafrost soil in the Arctic are subjected to dramatic annual changes in temperature, which may control soil microbial activity and community structure. Despite this, little is known about seasonal changes in the active microbial community within arctic soil systems. We studied seasonal variation in the bacterial community by co-extracting DNA and RNA from 12 active layer soil cores from Svalbard, Norway, collected monthly over a year. 16S rRNA genes at the DNA and RNA levels were sequenced using Illumina HiSeq technology and analyzed using QIIME. Multivariate statistical analysis of the bacterial diversity data showed distinct seasonal changes in the community at DNA as well as RNA level. It was observed that the relative abundance of presumably active Alphaproteobacteria increased over the summer and then dropped from October to November; and at the same time the relative abundance of presumably active Acidobacteria increased. Analysis of the bacterial community structure and physico-chemical parameters of the soil samples revealed that the bacterial community structure at the DNA level was significantly correlated with pH, soil water content. The community structure at the RNA level was significantly correlated with dissolved organic nitrogen, pH. In conclusion, the structure of the bacterial community in Svalbard active layer showed seasonal variation and was controlled by changes in pH and soil nutrient contents. presumably representing the active part of the community; e.g. the June RNA sample was dominated by Cyanobacteria.