Ecology under lake ice

Winter conditions are rapidly changing in temperate ecosystems, particularly for those that experi-ence periods of snow and ice cover. Relatively little is known of winter ecology in these systems,due to a historical research focus on summer ‘growing seasons’. We executed the first global quan-titative synthesis on under-ice lake ecology, including 36 abiotic and biotic variables from 42research groups and 101 lakes, examining seasonal differences and connections as well as how sea-sonal differences vary with geophysical factors. Plankton were more abundant under ice thanexpected; mean winter values were 43.2% of summer values for chlorophyll a, 15.8% of summerphytoplankton biovolume and 25.3% of summer zooplankton density. Dissolved nitrogen concen-trations were typically higher during winter, and these differences were exaggerated in smallerlakes. Lake size also influenced winter-summer patterns for dissolved organic carbon (DOC), withhigher winter DOC in smaller lakes. At coarse levels of taxonomic aggregation, phytoplanktonand zooplankton community composition showed few systematic differences between seasons,although literature suggests that seasonal differences are frequently lake-specific, species-specific,or occur at the level of functional group. Within the subset of lakes that had longer time series,winter influenced the subsequent summer for some nutrient variables and zooplankton biomas