Trapped in the ice: the formation of liquid water layers within lake ice and the effect on phytoplankton communities

Winter lake ice conditions are undergoing rapid changes because of alterations in global and regional hydroclimatic conditions. The traditional understanding of lake ice growth and evolution through a winter period is the downward progression of ice until air temperatures rise and melt, and breakup ensues. A unique meteorological condition of substantial mid-winter warming in the foothills of the Canadian Rockies allowed for the identification of a phenomenon where a liquid water layer was trapped between ice layers near the surface of a lake. Phytoplankton analysis identified that the interstitial water layer had a bloom of motile phytoplankton belonging to the order Chlamydomonadales . Stable isotopes suggest the upward movement of pelagic water in combination with landscape runoff contributed to the formation of the interstitial water layer. This study provides new insights and illustrates the complexities involved in understanding the physicochemical and biological mechanisms involved in shaping the winter ecology, as well as subsequent ice-free periods, of lakes under a changing climate.