Thunder Bay

'Rock snot' could signal trouble in Lake Superior, scientist says

Max Bothwell says gooey algae blooms suggest phosphorus levels are very low, and fish production could decline.

Environment Canada researcher Max Bothwell says gooey algae blooms suggest phosphorus levels are very low

So-called "rock snot" was discovered for the first time this summer in the St. Marys River. (Michel Chouinard/Queen's University)

A research scientist with Environment Canada says the recent appearance of so-called "rock snot" in the St. Marys River could point to a problem in Lake Superior.

Max Bothwell said the gooey algae blooms, called Didymosphenia geminata, are only known to appear when phosphorous levels are very low.

"Phosphorus is the key element that controls the overall productivity of many ... fresh water aquatic systems," Bothwell said. 
Environment Canada research scientist Max Bothwell said so-called "rock snot" in the St. Mary's River indicates low levels of phosphorus in Lake Superior. That could negatively impact fish production, he said. (supplied. )

"If phosphorus becomes very low, then it means that the overall productivity of that lake, ultimately culminating in fish production, will decline.  How much so is unknown ... but it does mean that there's a stress on the system from extremely low phosphorus," he said.

Bothwell noted, however, that those concerned with water clarity might view low phosphorus levels as a good thing, because they result in clearer water.

"There would be less phytoplankton algae in production in the lake," he explained. 

Data from Environment Canada suggests concentrations of phosphorus have been declining in Lake Superior for a decade now, Bothwell said, adding that those low levels are now flowing into the St. Marys River, resulting in what's believed to be the first appearance of rock snot in the river this summer. 

Scientists don't know for sure why the phosphorus levels are sinking, he said. 

Until they do, nothing can be done to address the situation because they don't know what they're addressing, he added.

The next step, Bothwell said, is to continue monitoring the situation to see if it remains stable or gets better or worse in the coming years.