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Diving Sinkholes For Microbial Mats That Bury

Diving Sinkholes for Microbial Mats that Bury Carbon and Release Oxygen

Dear everyone:

June 11, 2019: Onboard NOAA’s R/V Storm, Grand Valley State University researcher Tony Weinke is examining an intact 1-foot tall sediment core brought up by the Thunder Bay National Marine Sanctuary divers from the Middle Island Sinkhole in Lake Huron at a depth of ~79 feet.  Here, physiologically versatile cyanobacterial mats thrive on the lake floor in ground water emerging from Paleozoic marine evaporites containing high-sulfur and low-oxygen.  The sediment core is topped by bright purple photosynthetic cyanobacterial mats overlying organic carbon-rich sediments.  Preliminary estimates suggest a very high rate of sediment accumulation in the sinkhole of as much as 1 foot in just 300 years!  We’re are trying to figure out if the microbial communities thriving in such high-sulfur, low-oxygen modern-day refugia provide a window into the distant past when microbial life began burying organic carbon and oxygenating the ancient Archean and Proterozoic seas.  

—Bopi Biddanda and Ian Stone, Annis Water Resources Institute, Grand Valley State University, Muskegon, Mich. (;

—Wayne Lusardi and Phil Hartmeyer, Thunder Bay National Marine Sanctuary, Office of National Marine Sanctuaries, National Oceanic and Atmospheric Administration, Alpena, Mich. (

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