Arctic warming drives striking 21st century ecosystem shifts in Great Slave Lake (Subarctic Canada), North America’s deepest lake

Great Slave Lake, one of the world’s largest and North America’s deepest
lake, has undergone an aquatic ecosystem transformation in response to
21st-century accelerated Arctic warming that is unparalleled in at least
the past two centuries. Algal remains from a series of high-resolution
palaeolimnological records retrieved from the West Basin provide baseline
limnological data that we compared to historical limnological and
phycological surveys undertaken on Great Slave Lake between the 1940s and
1990s. We document the rapid restructuring of algal community composition
ca. 2000 CE that is consistent with recent increases in regional air
temperature, as well as declines in ice cover and wind speed, that would
collectively alter habitats for aquatic biota (e.g. thermal regime,
vertical mixing, turbidity, light and nutrients). This new limnological
regime initiated the first observation of scaled chrysophytes and favoured
the rapid proliferation of small planktonic cyclotelloid diatoms that
replaced the long-established dominance of large filamentous Aulacoseira
islandica in West Basin sedimentary assemblages. Such rapid
transformations in the primary producers of this socio-ecologically
valuable “northern Great Lake” may have widespread implications for the
entire food web with unknown consequences for aquatic ecosystem
functioning and fisheries, which many northern and Indigenous communities
depend upon.