Lake trout a harbinger of global contaminants
Many pollutants hitchhike to Lake Ontario on northbound winds and currents flowing from lower latitudes in Asia, Europe and North America.
Thu, Aug 02, 2012 at 04:35 PM
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.
About a decade later, DDT and PCBs were found in the blubber of Arctic ringed seals — which are consumed by polar bears, whales and people. DDT and PCBs were banned in the United States in the 1970s because they were accumulating in fish, birds and other wildlife around the country, wiping out some populations.
Then, in the late 1970s, flame retardants called polybrominated diphenyl ethers, or PBDEs, were detected in Lake Ontario’s lake trout. PBDEs were then confirmed in the Arctic in 1981 when the chemicals were found in ringed seals and whitefish. Amassing in the bodies of people and wildlife, they have been linked to altered hormones, reproductive effects and changes in developing brains. Their use has been phased out in recent years.
Now tests on trout and other organisms indicate that these legacy contaminants are decreasing in the Great Lakes environment, said Thomas Holsen, a professor at Clarkson University and primary investigator of the Environmental Protection Agency’s Great Lakes Fish Monitoring and Surveillance Program. And, following suit, a similar downward trend is happening in the Canadian Arctic, Muir said.
Yet despite the bans, they still remain at high levels in some Great Lakes fish and Arctic species.
“Concentrations of legacy contaminants in the Great Lakes are likely to continue to decline only slowly and pose a health concern,” says a 2010 study by University of Minnesota scientists.
Just like the older contaminants, Dechlorane 602 is now found around the world.
“Dechlorane 602 has also been detected in Western Africa, Europe, India, China and Tasmania, and is considered a global contaminant,” Reiner said.
Other dechlorane compounds already were on the radar of those in the Arctic and Great Lakes. A 2009 study to determine the top 50 chemicals that are persistent and can accumulate in wildlife in those regions included Dechlorane Plus, a flame retardant produced in large volumes.
Dechloranes, which are produced by Occidental Petroleum Corporation, or OxyChem, off Lake Ontario in Niagara Falls, N.Y., have been showing up in the Great Lakes environment over the past five years.
Scientists don’t know much about Dechlorane 602. It was introduced in the 1960s as part of a suite of dechlorane flame retardants used to insulate wires and cables, nylon connectors in computers and plastic roofing material.
“People who are working in the Arctic are aware of it for sure,” Muir said. “But there is no standard to analyze it.”
Dechlorane 602, which is no longer produced in the United States, has a similar structure to mirex, which is concerning, said Heather Stapleton, an assistant professor of environmental chemistry at Duke University. Mirex, an insecticide, was banned by the EPA in 1976 because it was both highly toxic and accumulative in food webs.
“It’s kind of scary to think about these unknowns,” Stapleton said.
The EPA required OxyChem to test a new, related compound, Dechlorane Plus, for toxicity to aquatic life, and also test lab rats for reproductive and neurological effects. Last year, the EPA stated that the data “suggest that measurable toxicity to aquatic organisms will not occur.” In addition, no effects were found in the rats.
But uncertainties about dechlorane’s effects on human and wildlife health remain, which is troubling, said Ronald Hites, a chemistry professor at Indiana University who is part of a team measuring persistent organic pollutants at five locations in the Great Lakes. They have consistently detected Dechlorane Plus at all sites.
“That is the issue with the American chemical industry, it’s a reactionary system,” Hites said. “Show us that it kills someone or something and then we’ll take it off the market.”
The American Chemistry Council, which represents chemical manufacturers, including OxyChem, called Hites’ comment “irresponsible and unsupported.”
In an emailed response, a spokesperson for the council said if information arises about possible health and safety implications, the companies are required by law to provide that information immediately to EPA. They also have voluntarily conducted detailed toxicology tests for high-volume chemicals, including Dechlorane Plus. Member manufacturers “go to great lengths to make their chemicals safe – for industrial uses, for commercial uses, and for consumer uses,” the spokesperson said.
Since dechlorane is in Great Lakes trout and Arctic whales, it has been found in people, too. Breast milk of women in Ontario contains low levels of Dechlorane Plus, according to a study published in February. However, no human health studies have been conducted yet.
Detecting new contaminants in lake trout is of increasing concern because they are becoming a more popular sport fish as their populations rebound, said Jana Lantry, an aquatic biologist at the New York Department of Environmental Conservation. Inhabiting the deepest, coldest waters, they can grow as big as three feet in length and 30 pounds.
The last century has been tumultuous for lake trout. In Lake Ontario, the most eastern Great Lake, they struggled to survive overfishing at the turn of the 20th century. Then, in the 1950s, they were eliminated in Lake Erie and Lake Ontario by the non-native sea lamprey, which attached to them with their suction-cup mouths and literally sucked the life out of them. Around this time, the Niagara River shoreline was starting to fill with industry, which was pumping chemicals into the same waters that fisheries managers were trying to restock.
Lantry said over the past 15 years, with stocking programs, sea lamprey controls and pollution regulations, the population is rebounding in Lake Ontario and its tributaries.
In the Arctic, new and emerging contaminants bring unique concerns, said James Sloan, a professor emeritus of atmospheric science at the University of Waterloo and researcher at Canada’s Polar Environment Atmospheric Research Laboratory.
With its cold climate, the Arctic acts like a toxic repository.
“Things like pesticides, flame retardants … often have low vapor pressure so they evaporate in warm weather and are airborne and carried by atmosphere mostly to the north,” Sloan said. As the temperature goes down, they condense and then drop to the icy surface, where they are taken up by organisms at the bottom of food chains. “When they get to low temps of the Arctic they never evaporate again.”
The ice cap is “like keeping a cork on a bottle” that stops the chemicals from leaving the water and returning to the atmosphere, Muir said.
Beluga whales are able to build up contaminants more so than other wildlife because of their excess fat, where contaminants are stored, and their long lives. People in indigenous communities in Canada rely on them for food.
The Inuit in Canada and Greenland are the world’s most contaminated people, and studies have linked consumption of their chemical-tainted native foods to immune suppression, infections and learning problems in children.
“Arctic biota, particularly the high fat portions of the animals, are part of the traditional diet of indigenous populations, and can result in greater exposures for Arctic peoples than those in temperate latitudes,” Reiner said.
Testing people and whales under the harsh conditions of the Arctic is complicated and costly.
But the lake trout has been a good stand-in. For half a century, the world has been monitoring this fish’s performance as it darts around the theater of the Great Lakes. And scientists say with new contaminants showing up all the time, its starring role isn’t about to end anytime soon.