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Scientists study Middle Island sinkholes

ALPENA — The Middle Island sinkholes continue to be an ideal situation of isolation for researchers.

University of Michigan researcher and doctoral student Sharon Grim said scientists have studied the sinkhole three times a year since 2001.

Last week they finished another round of research.

“We think it’s a great model system how early earth microorganisms changed the planet,” she said.

She said because of the lack of oxygen in the sinkholes it makes it hard for fish and other predators to survive. Grim said U of M collaborates with other schools such as Grand Valley State University, Indiana University, Purdue University, the University of Chicago and more. These scientists partner with the Thunder Bay National Marine Sanctuary which provides research vessels and divers to assist.

Sanctuary maritime archeologist John Bright said this kind of research is an extension of what they study.

The sinkholes were created due to a unique geology, he said.

“The local geology the region has a lot of limestone,” he said. “Limestone in the presence of water will slowly dissolve. It creates little passageways for groundwater to move and as it’s dissolving it picks up dissolved minerals from the rocks. So where this ground water travels through the aquafir sinkholes are produced. Enough of the limestone geology has been eroded away or dissolved but is no longer able to bear the weight of the rock or earth above it and it just collapses. When it collapses it creates a direct path for groundwater that’s traveling through the aquafir to come up directly into the lake.”

There’s an abrupt difference between the chemistry of the lake water and the chemistry of the groundwater that’s been traveling through the rock and compound, he said.

Grim said they want to understand how the sinkhole microbial community work together, their metabolism, how they influence their ecosystem and how it influences them.

“They’re looking at DNA sequences in the microbial mat, how they synthesize proteins, the kind of functions they’re doing, measuring micro scale. Coupling all those measurements together get a better picture of how they’re doing,” she said.

Members of the dive team will dive about 77 feet down in 42 degree water to the sinkholes to collect sediment, measure the temperature and chemistry of the water.

“We rely on their accounts how it feels when they’re down there. They are eyes, ears and hands in the sinkhole,” she said.

Bright said the divers are experienced ones who are careful not to disturb the area.

Grim said every year the research leads to new questions to solve or study.

“It’s really through this collaborative effort to further develop this project. With the help of the sanctuary and all the other schools,” she said. “It’s really been exciting for me as a Ph.D. student to work on everything.”

Jordan Spence can be reached via email at jspence@thealpenanews.com or by phone at 358-5687.