Imagine a huge mountain of volcanic rock, completely submerged by water and laying in the middle of an inland sea.
That description largely sums up the Superior Shoal — an underwater mountain that rises nearly 300 metres from the bottom of Lake Superior.
First charted in 1929, Superior Shoal is also entirely within the world’s largest freshwater conservation area and is 70 kilometres from the closest shoreline. Its remote location in the centre of Lake Superior has left it something of a mystery.
WATCH | The Superior Shoal in the middle of Lake Superior:
However, a research team from Lakehead University in Thunder Bay, Ont., and a film crew explored the shoal in early September. The expedition was tasked with collecting valuable data about the role this massive underwater structure plays on the lake’s ecosystem.
The shoal is a unique structure that could play a key part in understanding Lake Superior’s ecosystem, said Michael Rennie, a Lakehead University associate professor and research fellow at the International Institute for Sustainable Development-Experimental Lakes area.
“This is such a unique spot and it’s this crazy mountain in the middle of Lake Superior,” said Rennie. “There are a couple of other spots like this throughout the Great Lakes, and what we’ve sort of come to learn is much like seamounts in the oceans, these are hotspots of biodiversity and fish productivity.”
Supported by a Canadian government grant, Rennie and his six-member science team travelled to the Superior Shoal from Duluth, Minn., on a research vessel called the Blue Heron.
The team worked and slept on the 83-foot trawler over the nine-day expedition. Rennie said there was much to do during that time.
“A lot of what we were trying to understand on Superior Shoal is how physical processes like currents, waves and light penetration interact with the biological community,” said Rennie, “and how that might be involved in supporting the biological community that exists here. Some of those physical processes involve upwelling as well as the deposition of material from the water column through back eddies and currents that happen that go over the shoal.”
Superior Shoal may play an important role in the health of the Lake Superior trout fishery, said Rennie, noting that redfin, leans and siscowet are among the several unique strains of lake trout that call the shoal home. He said these stocks also survived the crash of the fishery due to lamprey and overfishing in the 1960s and ‘70s.
“These places like Superior Shoal, no one ever stocked fish there,” said Rennie. “And those populations have recovered more or less on their own. So do these fish genetically best represent the lake trout that used to be in Lake Superior before the collapse in the ‘60s?”
Although Rennie’s research was the focus of the expedition, the entire nine days were also documented.
Also aboard the Blue Heron were filmmakers from Bruce County in southern Ontario.
Yvonne Drebert and Zach Melnich are the award-winning duo behind Inspired Planet Productions and are both fellows with the Royal Canadian Geographical Society.
“We basically begged Michael to take us,” laughed Melnick. “This area has very rarely been explored on camera.”
Melnick said they had been curious about lake protrusions like the Superior Shoal after exploring one while filming their series and related documentary All Too Clear: Beneath the Surface of the Great Lakes. That documentary examined how invasive zebra and quagga mussels had changed the food dynamic in the Great Lakes.
The filmmakers also wanted to see if they could film some trout strains that are an important part of Lake Superior’s fishery.
“One fish we were hoping to see when we got to the Superior Shoal was the redfin,” said Drebert. “And this is a lake trout with giant fins, a big tail and a gorgeous red colouring. And what we think the redfin does is kind of sail around these underwater mountains using their giant fins the way eagles will soar around a mountain using upwelling currents.”
To get to the depths required on the shoal, and with the best clarity possible, the filmmakers used a 27-kilogram, high-tech underwater robot — or a remotely operated vehicle (ROV).
The ROV has an acrylic dome on the front that can handle intense pressure as it gets deeper. It also corrects the optics underwater and has the same kind of camera used to film animals in the moonlight.
This robotic drone, built in partnership with Boxfish Robotics, in New Zealand, can go about 500 metres in depth and has eight thrusters. Melnick said the robot can spend hours under water and can swim like a fish.
“We try to mimic fish behaviour with the robot as well,” said Melnick. “We found that the lake trout, especially out at the Superior Shoal, were very friendly with the robot. So they would come up and be curious, and look at it just like you would imagine, like a seal or something in the ocean might. And so that was super cool.”
Drebert said you can’t send a signal through the water the same way you can through the air with an aerial drone, so the ROV is always connected via a fibre-optic tether. On the Blue Heron, Drebert would feed out the tether and Melnick would control the ROV from a room full of screens. From here, he could drive the ROV, watch what was being filmed and keep track of location via GPS.
Melnick said the footage shot on the Superior Shoal will be part of a new series called Hidden Below: the Freshwater World that he says will be coming to TVOntario in a couple of years. He said they’re also making a science documentary that will explore the importance of lakemounts and why they should be protected more, like seamounts are protected in the oceans.
Drebert said exploring Superior Shoal brought home its size and vastness.
“I think for folks who are living in Thunder Bay or in Nipigon, looking out at the archipelago and seeing the cool islands and how they’re structured, imagine all that just under water going deep, deep down,” she said. “It was really great to be able to visualize what these mountains actually look like.”
