Great Lakes Trout Serve as Barometer for Global Pollutants

Image: flickr/Neil916

When one thinks of iconic fish, Lake Ontario?s lake trout probably don?t come to mind.

They don?t have the spear of a marlin or the taste of a tuna. There are no singing, dancing lake trout hanging on cabin walls. Great Lakes anglers often catch them while targeting the more popular chinook and coho salmon.

But the white-bellied natives of these deep, cold transnational waters have a unique reputation ? one considerably nobler than taking bait or adorning plates: They are a barometer for global pollutants.

For almost 50 years, whenever chemicals have shown up in the lake trout of Lake Ontario, they also have contaminated animals and people throughout the Great Lakes and farther north, in the Arctic.

Its role as a toxic harbinger, begun in the late 1960s, continues as researchers recently discovered another unfamiliar flame retardant ? Dechlorane 602 ? in the trout and in the Canadian Arctic?s beluga whales. This study, the first to detect dechlorane compounds in Arctic wildlife, shows that Dechlorane 602 is persistent in the environment, migrates long distances and accumulates in the food web.

Levels of the compound were higher in Lake Ontario?s lake trout than in beluga whales, according to Eric Reiner, lead study author and scientist at the Ontario Ministry of the Environment. But finding a relatively unknown compound in the whales is of concern because little is known about its possible health effects and belugas are a traditional food source of the Inuit.

It?s yet another suggestion that what happens in the Great Lakes doesn?t stay in the Great Lakes.

Many contaminants hitchhike to the Arctic on northbound winds and currents flowing from lower latitudes in Asia, Europe and North America. Lake Ontario spills into the Atlantic Ocean via the St. Lawrence Seaway. Transport times in the atmosphere are short, so regions like the Hudson Bay could receive contaminants from the Great Lakes within two or three days, said Derek Muir, a senior research scientist with Environment Canada.

Just because the compounds are found in both regions doesn?t necessarily mean the chemicals in the Arctic are from Lake Ontario. ?The Great Lakes are important, but not the sole source,? Muir said. Past studies show that a lot of the contaminants in the high Arctic are from Asia, he said.

Known for their light-colored spots and deeply forked tail, lake trout are the most frequently tested Great Lakes fish, chosen because they would be among the most contaminated creatures.

?Lake trout are often used as they are known as apex species,? Reiner said. ?They are at the top of the aquatic food web and concentrations of bioaccumulative compounds tend to be highest in such species.? Each step up the food web, contaminants taken in by an animal can magnify by twentyfold or more. That means a top predator fish like a lake trout can carry a chemical load hundreds of times higher than a tiny bottom organism has taken in.

If an industrial chemical or a pesticide is found in Lake Ontario?s trout, this typically is a warning sign for scientists and policymakers: It likely means the compound is slow to break down, is accumulating in top predators and is moving globally. Those three factors can turn a pollutant into an international environmental problem on the scale of DDT and PCBs.

Discovery of the little-known flame retardant Dechlorane 602 is the latest example of lake trout, Salvelinus namaycush, serving as a glimpse into the future.

In the late 1960s, it was reported that the pesticide DDT was hurting lake trout reproduction in Lake Ontario and throughout the Great Lakes. Not long after, industrial compounds called polychlorinated biphenyls or PCBs were found to be contaminating lake trout populations as well.

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