The Middle Island sinkhole is open to Lake Huron, creating a gradient of biological activity. A nine-metre boat is also visible in this aerial photo for sense of scale. (Scott Kendall/Bopi Biddanda/Grand Valley State University)
CBC.CA
February 25, 2009
by Sharon Oosthoek
Twenty metres below the surface of Lake Huron, scientists have discovered peculiar sinkholes where a bizarre ecosystem at odds with the rest of the lake flourishes.
The huge lake’s freshwater fish shun the dense, salty, oxygen-deprived waters of these sinkholes off northeastern Michigan.
Instead, brilliant purple mats of cyanobacteria — cousins of microbes found at the bottom of permanently ice-covered lakes in Antarctica — and pallid, floating, ponytail-like microbes thrive.
Groundwater from beneath the lake is dissolving minerals from the ancient seabed and carrying them into the lake to form these exotic, extreme environments, says aquatic ecologist Bopaiah Biddanda of Michigan’s Grand Valley State University, a leader of the team studying the sinkhole ecosystems.