Tails full of metal: Tadpoles picking up toxics from Queensland coal mines
Queensland coal mine waste affects tadpole behavior and survival and leaves them full of toxic metals
February 22, 2016
By Brian Bienkowski
Environmental Health News
Tadpoles exposed to coal mine wastewater in Queensland, Australia, had delayed development, hyperactivity and ended up full of toxic metals in their tails and livers, according to a new study.
The study, published in the Aquatic Toxicology journal last month, is concerning as Queensland is a major coal mining region. It comes amid increasing concern about amphibian population declines throughout the world and adds to evidence that pollution may play a key role.
“Amphibians are currently some of the most threatened organisms on the planet,” said Central Queensland University researchers and co-authors Chantal Lanctôt and Steven Melvin in a joint emailed response.
Camouflaged in earthy colors, striped marsh frogs live along the western half of Australia. Their call is an abrupt pop, like a racquetball return. Frogs and other aquatic animals hang out in wetlands near the holding dams where, during extreme rain or flooding, discharges of the mine waste can escape into the environment.
For four weeks the researchers exposed striped marsh frogs to 25, 50 or 100 percent coal mine wastewater from two dams in Central Queensland, Australia—an area known for heavy coal mining. All exposed tadpoles had hyperactivity, and elevated levels of selenium, cobalt and arsenic in tails and liver tissue. Those exposed to 100 percent wastewater were smaller as well.
None of the unexposed tadpoles died. But in the groups exposed to 50 percent and 100 percent wastewater, 40 percent and 55 percent of the tadpoles died, respectively.
Coal mining wastewater contains metals, hydrocarbons and salts that can impact the amphibians’ oxidative stress and mess with their hormones, Lanctôt and Melvin said. “These can, in turn, result in delayed development, altered swimming behavior, and even reduced survival.”
Striped marsh frog populations appear to be stable. But the findings don’t bode well for amphibians.
Two main things are influenced by altered swimming and activity—“foraging and predator avoidance,” said Christopher Salice, an assistant professor and researcher at Towson University who studies environmental impacts on amphibians.
“Acquiring resources and preventing them from being a resource,” added Salice, who was not involved in the study.
The study had some limits—for example, they only used one mass of eggs, which limits the genetic variability. The ones used “could have been more sensitive or more resistant” to pollutants, Salice said.
But there is a complex interplay of factors affecting developing baby frogs, including species competition, habitat loss and climate change. The recent striped marsh frog findings add to a growing body of science that suggests coal waste might tip the balance, leading to declines in certain areas.
|Black coal deposits in Queensland (Credit: Minerals Council of Australia)|
For instance, researchers reported in 2014 that Blacksmith tree frogs from coal mining areas in Brazil had elevated levels of sulfur, chlorine, iron, zinc and bromine, and their antioxidant systems were sensitive to the pollution.
And Southern leopard frogs and Southern toads that emerged from areas contaminated with coal waste had concentrations of arsenic, selenium and strontium up to 35 times higher than those from unpolluted wetlands, according to a 2005 University of Georgia study.
The current research carries extra weight because of where it was done—Queensland, which sits on the northeast coast of Australia and is a major coal mining region. The Australian government estimates there are two deposits of coal in the area that are more than five billion tons, five deposits between three and five billion tons and dozens more smaller deposits dotting the region.
The Bowen Basin in central Queensland has more than 50 active mines in a 29,000 square mile area, according to the Queensland Government’s Department of Natural Resources and Mines.
Queensland has been under fire for its widespread coal mines and associated pollution. According to Australia’s National Pollutant Inventory, central Queensland coal mines are nine of the top 10 emitters in the region for PM10, toxic air particulates greater than 10 micrometers or less in diameter. Coal mines in Australia account for almost half of such emissions, and PM10 emissions have doubled in the past five years, according to Environmental Justice Australia.
A survey released in December by 350.org of 1,500 people in Australia found 68 percent of respondents agreed Australia "needs to restrict coal mining because of the impact that it is having on our natural environment and biodiversity."
The Minerals Council of Australia, which oversees the country’s coal mines, did not respond to numerous requests for comment.
Lanctôt and Melvin said “under normal circumstances, wastewater releases will be carefully controlled and limited to periods of high rainfall, as a means of reducing risks to wildlife” but added that accidental releases can happen.
And the pollution can stay with the creatures a lifetime, Salice said.
“Even if the initial effects of pollution don’t last [in tadpoles], it still might be a signature of something else,” he said. “Once they turn into terrestrial frogs everything that has happened to them is carried with them.”
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