Not too long ago, Michigan researchers discovered previously unknown sink holes in Lake Huron, some of which are hundreds of feet deed, reaching down to Paleozoic era bedrock. When scientists went in to investigate them, they discovered entirely new ecosystems down there, thriving in dark anaerobic (no-oxygen), mineral rich environments.
“You have this pristine fresh water lake that has what amounts to materials from 400 million years ago … being pushed out into the lake,” said Steven A. Ruberg,
Similar to the undersea vents, these sink holes harbor odd bacteria adapted to extreme environments. They grow in large "pony-tails" or in purple towers along the bottom.
The Lake Huron sinkholes are dominated by brilliant purple mats of cyanobacteria -- cousins of microbes found on the bottom of permanently ice-covered lakes in Antarctica -- and pallid, floating pony-tails of other microbial life, according to the journal article.
The saltwater venting out of the sinkholes is hostile to most life forms because it lacks oxygen, the scientists said in the article..
Newer studies show that the water venting from the bottoms of the sink holes is warmer than the surrounding waters by an average of 5 to 10 degrees fahrenheit, with several orders of magnitude more minerals than the surrounding waters.
biogeochemical conditions (See above table). The venting water was 3.5°C warmer than the surrounding water and had 10-fold higher concentrations of chloride, 100-fold higher concentrations of sulfate, and 1000-fold higher concentrations of total phosphorus.
The vent water also contained 5-fold higher concentrations of dissolved organic carbon (DOC) and 400-fold higher concentrations of particulate organic carbon (POC)relative to the surrounding lake water
These sink holes are a pretty new field of study...so the information will be ongoing.