Decreased Snow Cover Stimulates Under-Ice Primary Producers but Impairs Methanotrophic Capacity

• Published in: mSphere 2019-01, Vol.4 (1)
• Main Authors: Garcia, Sarahi L, Szekely, Anna J, Bergvall, Christoffer, Schattenhofer, Martha, Peura, Sari
• Format: Article
• Language: English
• Subjects: Abundance; Algae; Applied and Environmental Science; Bacteria - growth & development; Cell division; Chlorophyll; Climate Change; Deoxyribonucleic acid; DNA; Experiments; Gas exchange; Genetic testing; greenhouse gas; Greenhouse gases; Heterotrophic bacteria; Ice; Laboratories; lakes; Lakes - chemistry; Lakes - microbiology; Light; Light penetration; Methane; Methane - metabolism; Methanotrophic bacteria; methanotrophs; Microbiology; microorganisms; Mikrobiologi; Oxygen - analysis; Primary production; Seasons; Snow; snow cover; Snow removal; Temperature; Water column; Water temperature; Winter
• ISSN: 2379-5042; 2379-5042
• DOI: 10.1128/msphere.00626-18

Climate change scenarios anticipate decreased spring snow cover in boreal and subarctic regions. Forest lakes are abundant in these regions and substantial contributors of methane emissions. To investigate the effect of reduced snow cover, we experimentally removed snow from an anoxic frozen lake. We observed that the removal of snow increased light penetration through the ice, increasing water temperature and modifying microbial composition in the different depths. Chlorophyll and concentrations increased in the upper water column, suggesting activation of algal primary producers. At the same time, , one of the key photosynthetic bacterial families in anoxic lakes, shifted to lower depths. Moreover, a decrease in the relative abundance of methanotrophs within the bacterial family was detected, concurrent with an increase in methane concentration in the water column. These results indicate that decreased snow cover impacts both primary production and methane production and/or consumption, which may ultimately lead to increased methane emissions after spring ice off. Small lakes are an important source of greenhouse gases in the boreal zone. These lakes are severely impacted by the winter season, when ice and snow cover obstruct gas exchange between the lake and the atmosphere and diminish light availability in the water column. Currently, climate change is resulting in reduced spring snow cover. A short-term removal of the snow from the ice stimulated algal primary producers and subsequently heterotrophic bacteria. Concurrently, the relative abundance of methanotrophic bacteria decreased and methane concentrations increased. Our results increase the general knowledge of microbial life under ice and, specifically, the understanding of the potential impact of climate change on boreal lakes.