The Arctic is covered with lakes that freeze over for a significant part of the year. Ice formation leads to the establishment of a distinct environment within the lake relative to the open-water period by limiting gas exchange at the air-water interface, wind-driven mixing (Denfeld et al., 2018), allochthonous input of terrestrial carbon and nutrients (Bertilsson et al., 2013), and also reducing the amount of light penetrating through the water column (Kirillin et al., 2012). All of these factors-light penetration, nutrient concentrations, and thermal structure of the water column-affect biomass and community structure of phytoplankton. Despite the fact that ice covers Arctic lakes for the majority of the annual cycle, most of what we know about phytoplankton communities and biogeochemical dynamics in these lakes is based on the open-water season. Considering the rapid changes in climate affecting phenology, ice-out dates, and abiotic conditions