To my delight, I found this morning among the recommended diaries on Daily Kos an entry discussing recent and surprising findings of some very unusual and unexpected Great Lakes aquatic microenvironments. Given that the site is primarily given to unapologetically partisan political matters, I always am pleased when environmental matters grow legs there.
Anyhow, scientists are learning more about these fairly large sinkholes on the floor of Lake Huron; the extremely dense, mineral-rich, highly-electrically-conductive water that settles into these features would normally be thought hostile to life, but as we have seen in other such seemingly hostile environments–marine and terrestrial alike–life itself as an irrepressible force manages to find a way.
From a pair of articles linked in the DK diary:
The sinkholes are formed by salty groundwater seeping into the lake and dissolving the ancient underlying seabed, said Bopaiah A. Biddanda of Grand Valley State University’s Annis Water Resources Institute. They are similar to deep sea vents on ocean bottoms.
The sinkholes Biddanda found are offshore of Alpena in about 65 feet of water. He co-wrote an article about them in the current edition of Eos, the journal of the American Geophysical Union.
The sinkholes are home to “bizarre” ecosystems dominated by brilliant purple mats of cyanobacteria, or blue-green algae – cousins of microbes found on the bottom of permanently ice-covered lakes in Antarctica according to the journal article.
and from Grand Valley State University’s Annis Water Resources Institute (go check the video clips, too):
Karst sinkholes discharging groundwater onto the Lake Huron floor through Paleozoic bedrock have created unique habitats characterized by steep environmental gradients and conspicuous benthic microbial mats and organic-rich sediments. These ecosystems feature high microbial biomass and intense activity – biogeochemical hot spots.
All the more astonishing, to me anyway, is that within the framework of geologic time, surface water features (rivers, lakes) are fleeting. The Great Lakes are only about 15,000 years old–the blink of an eye in comparison to the 4-plus billion. The capacity for critters to adapt to and capitalize upon conditions that deviate so wildly from normal is truly something to behold.