Abstract: More than half of global lakes are seasonally or annually frozen. Freeze is a special physical-hydrological process in frozen lakes, affecting physical and chemical variables of lake ecosystems. Many ecological issues caused by climate warming and lake eutrophication have attracted global attention, including the shortening frozen period, phytoplankton phenological shifts and earlier spring algal blooms. We reviewed the important progress of phytoplankton research during the frozen period in lakes from three aspects. First, we summarized recent progress in various environmental conditions and the variations of physicochemical factors in different stages of frozen period. We then synthesized the temporal and spatial variations of phytoplankton growth, species composition, and community structure under changing environment during the frozen period, as well as their response mechanism. Lastly, we introduced the research progress on phytoplankton during the frozen period in China. Accordingly, the future trends of phytoplankton research during the frozen period are prospected, especially biogeochemical processes, feedback mechanism among lake-atmosphere-land and climate, research methods, and the construction of theoretical models.

Key words: frozen period, lake, phytoplankton, environmental change.