A U.S. Geological Survey study shows that aquatic plants, fish, and other animals living in the Grand Canyon contain high levels of mercury and selenium. Though the toxic chemicals are within limits that are considered safe to humans, researchers say that the find signals that wildlife is no longer safe in the remote canyon.
Researchers explained that polluted water from the Lake Powell, reaches Glen Canyon Dam and flows downstream to the Colorado River in the Grand Canyon. Unfortunately, toxic elements from waste water are absorbed by plants, fish, and other wildlife in the canyon. And high levels of mercury are particularly risky to humans, too, since rainbow trout is a very popular dish among local anglers.
USGS scientists explained that Colorado River is no longer a safe heaven for wildlife despite it being one of the most remote ecosystems in the country. The high concentrations of mercury found in the animals and plants of the Grand Canyon are an explanation to low reproductive rates, stunted growth, and low rate of survival of species living in the region.
Selenium has also natural sources, but mercury must have traveled half-a-globe to the Grand Canyon, researchers believe.
One piece of good news is that large specimens of rainbow trout are not affected. High concentrations of the toxic elements were only detected in small fish. The team said that it took samples from six different sites in the Grand Canyon, and the findings pointed into one direction – big trout is not as exposed to chemical pollution as smaller trout is.
And researchers even have an explanation to the phenomenon. They argue that small trout can feed on insects and need no other source of calorie. On the other hand, larger trout needs also feed on algae because the dwindling populations of bugs in the area are not enough to cover all its nutritional needs.
But insects carry considerable amounts of mercury. For instance, blackflies, which are trout’s favorite dish, were also found to contain high levels of mercury. Biologists believe that the insects feed on the mercury-laden algae in Lake Powell and ”export” the neurotoxin all the way into the Grand Canyon.
Ted Kennedy, one of the researchers involved in the study said that mercury levels found in fish in both Glen Canyon and the Grand Canyon are within safe limits for human consumption.
The USGS study is the first to focus on polluters in the Grand Canyon. Scientists were particularly interested in trout because people prefer to consume it. Nevertheless, the team analyzed five other species of fish and still found risky levels of mercury and selenium in them. Yet, there’s a bright side of selenium intoxication. Selenium protected animals from developing deformities when absorbing too much mercury which is a neurotoxin.
Image Source: Pixabay
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