Scubaism

After becoming so badly polluted it was labelled a “dead lake” in the 1960s, few would have imagined the waters of Lake Erie would one day be compared to the vibrant hues of the Caribbean.

But in an ironic twist of fate, a destructive invasive species that entered the Great Lakes about 20 years ago has created increasingly clear waters, leaving many to reasonably assume the lakes keep getting cleaner and healthier.

But it’s just an illusion created by the zebra mussel - a tiny interloper that’s killing off life under the surface even as it continues to make all the Great Lakes look more and more picturesque.

Zebra mussels are filter feeders and each one can process about one litre of water each day, sucking out plankton and other organic matter. It leaves the water cleaner but it also robs other aquatic life of a food source, which has a trickle-down effect on the food chain.

Less organic matter in the water also allows the sun to penetrate deeper, which results in increased water clarity.

Visitors love the gorgeous clear water, making it difficult for tourism operators to curse the zebra mussels.

“The one thing the zebra mussels have done is they’ve certainly cleaned up the lakes, there’s no doubt about that,” Milly Coulphart, general manager of the Port Dover Board of Trade, said.

But the zebra mussels have also pushed fish from their natural homes in the lake, forcing them to seek out darker areas, which again can have an effect on the food chain and the ecosystem of the waters.

“When zebra mussels and their large colonies that you get on the bottom cover a lot of the rocks, they also cover all the crevices,” Francine MacDonald of the Ontario Federation of Anglers and Hunters said.

The creatures that used to live in those rocks were food for fish, but they’re getting harder and harder to find.

“Whitefish, for example, have missed out on this important food source and their growth rate is much lower, they’re not as big as they were before because they lost that really high nutrient-rich source that is now not available,” she said.