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Intensified warming in the Arctic and Subarctic is resulting in a wide range of changes in the extent, productivity, and composition of aquatic and terrestrial ecosystems. Analysis of remote sensing imagery has documented regional changes in the number and area of ponds and lakes as well as expanding cover of shrubs and small trees in uplands. To better understand long-term changes across the edaphic gradient, we compared the number and area of water bodies and dry barrens (>100 m2) between 1956 (aerial photographs) and 2008–2011 (high-resolution satellite images) for eight ∼25 km2 sites near Nejanilini Lake, Manitoba (59.559°N, 97.715°W). In the modern landscape, the number of water bodies and barrens were similar (1162 versus 1297, respectively), but water bodies were larger (mean 3.1 × 104 versus 681 m2, respectively) and represented 17% of surface area compared with 0.4% for barrens. Over the past 60 years, total surface area of water did not change significantly (16.7%–17.1%) despite a ∼30% decrease in numbers of small (2) water bodies. However, the number and area of barrens decreased (55% and 67%, respectively) across all size classes. These changes are consistent with Arctic greening in response to increasing temperature and precipitation. Loss of small water bodies suggests that wet tundra areas may be drying, which, if true, may have important implications for carbon balance. Our observations may be the result of changes in winter conditions in combination with low permafrost ice content in the region, in part explaining regional variations in responses to climate change.

A new centric diatom genus is described from laminated freshwater sediments of Middle Eocene age near Horsefly, British Columbia, Canada. This diatom, Eoseira wilsonii gen. et sp. nov., grew in filaments that constitute dense monospecific sub-horizons within the white couplets that represent summer deposition in the varved sequence. Although Eoseira clearly belongs within the Family Aulacoseiraceae, several features distinguish its valve structure from Aulacoseira. Gigantism of spines and the lack of geometric relationships between spine position and mantle areolae are the most conspicuous features of the genus. Eoseira is among the oldest freshwater diatoms known and one of relatively few extinct freshwater genera. In addition to serving as a potential biostratigraphic marker, Eoseira is a cornerstone to undertanding the evolutionary trajectory of the Aulacoseiraceae, likely the oldest family of freshwater diatoms. As such, it refines our understanding of early radiations from the marine realm in western North America. Furthermore, paleoecological inferences based on Eoseira life strategy pertain directly to limnological conditions during early Cenozoic hot-house conditions.