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Lake Superior has a new native resident.
It’s been hanging around the shore for years, but until now it was regarded
as an intercontinental drifter, not a homegrown local. So say Rebecca Bixby
of the University of Georgia and fellow researchers Mark Edlund of the Science
Museum of Minnesota and Eugene Stoermer from the University of Michigan. In
the latest issue of Diatom Research, the scientists describe a new species
of diatom, Hannaea superiorensis, found primarily in Lake Superior. Prior to
its discovery, the new species of photosynthetic algae was combined with another
group of diatoms found in cold, pristine rivers and streams around the world.
This is now the only described species of the genus Hannaea that has adapted
to living in a lake environment and inhabits one lake in particular.
Diatoms are microscopic, single-celled algae with cell walls composed of silica.
The newly described diatom is boomerang-shaped and lives in unusual pincushion-like
colonies attached to rocks in the waves along the shore of Lake Superior. Bixby
likened the discovery in the well-studied inland waters “to finding a
new kind of tree on a street you've walked down a hundred times.”
“When you look at it carefully under the microscope and compare it to
other diatoms, it clearly is different from the other species it had previously
been grouped with,” said Bixby, a postdoctoral researcher with the UGA
Institute of Ecology. “Most obvious is the length -- Hannaea superiorensis
is nearly twice as long as other species in the genus Hannaea.”
To many people, diatoms are best known for their industrial uses. For years,
fossil deposits of diatoms called diatomaceous earth have been mined for uses
in filters, pesticides, insulation, paint, ceramic additives, and cleaning
abrasives. As scientists have learned how different species of diatoms respond
to different environmental conditions, though, these algae have become critical
to understanding how bodies of water are affected by climate change and human
impacts.
“What makes Hannaea superiorensis so special is that it is native and
endemic to Lake Superior -- it is not a new exotic species or an invader,” said
Bixby. The term “endemic” describes organisms distributed over
a particular, relatively limited geographic area. “It is unusual to find
new species that are native to the environment, compared to invasive species
that have been introduced to that environment. New endemics are more commonly
found in less explored regions like tropical rainforests or remote islands,
in part because they are often more sensitive to environmental change.”
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