Alpena, Mich. -- The research vessel Storm sits in the Thunder Bay National Marine Sanctuary -- in water is so clear you can just make out the bottom. Divers prep their gear on deck and then sink into the waters of Lake Huron.
In roughly a minute, they’re at the bottom of an 80-foot sinkhole. Down there, with almost no oxygen and a large amount of sulfate seeping up through the ground, it’s a perfect place for microbes to gather in layers along rocks. They form one of earth’s strangest organisms: microbial mats.