Breathing at Sleep: Respiration in Arctic Lakes During Polar Nights

Polar nights are unique periods to understand metabolism in ice-covered lakes from physical and biological perspectives. Despite the nearly zero primary production, polar nights cannot be disregarded as periods of biological stagnation, and recent data on biological processes and biogeochemical interactions are not yet fully understood, but can provide valuable information on lake ecosystem functioning in the absence of sunlight. Seasonally ice-covered Arctic Lake Kilpisjärvi at the latitude of 69° N experiences night time conditions from December to mid-January. Here, we use the continuous high-frequency time series of high-resolution temperature and oxygen from Kilpisjärvi to understand temperature and depth-related changes in respiration levels for three years from 2019 to 2022. In parallel, we aim to derive vertical microbial community composition by analysing water samples from different depths during the ice-covered period and correlate the outputs with oxygen dynamics to understand bacterial adaptations along biogeochemical gradients in Lake Kilpisjarvi.