Decreased snow cover stimulates under ice primary producers, but impairs methanotrophic capacity

Abstract

Climate change scenarios anticipate decrease of spring snow cover in boreal and subarctic regions. Forest lakes are abundant in these regions and substantial contributors of methane emissions. We performed an experiment on an anoxic frozen lake and observed that the removal of snow increased light penetration through the ice into the water modifying the microbial composition across depths. A shift in photosynthetic primary production was reflected by the increase of chlorophyll a and b concentrations in the upper depths of the water column, while Chlorobia, one of the key photosynthetic bacteria in anoxic lakes, shifted to lower depths. Moreover, a decrease in abundance of methanotrophs, such as Methylococcaceae, was noted concurrently to an increase in methane concentration in the water column. These results indicate that decrease of snow cover impacts both primary production and methane production/consumption, ultimately leading to increased methane emissions after spring ice off.