DEC 29, 2018 06:56 PM PST

Fish ear bones track coal ash contamination

Coal ash contamination is a public health threat across the United States. Coal ash refers to the toxic remains of coal burning in power plants. The chemicals in coal ash are known carcinogens and also cause developmental disorders and reproductive problems, according to Earth Justice. When coal ash gets into waterways and ecosystems, it leaves death in its wake, poisoning fish and wildlife. However, despite its known dangers, the Environmental Protection Agency has not taken major action to monitor and protect the waters we drink, so US waters remain contaminated.

But new research from Duke University published in Environmental Science & Technology Letters has unearthed a new tool to identify and track coal ash contamination – and it comes from an unlikely source: the ear bones of fish.

Jessica Brandt, the lead author of the paper, explained that her team used isotope ratios in fish ear bones (called otoliths) to analyze the presence of coal ash contamination in two North Carolina lakes that had been impacted by effluents from coal ash ponds at nearby power plants. "Calcified structures -- or otoliths -- found in a fish's inner ear are known to store a lot of life history information, including chemical and physical records of the fish's age, natal habitat, and migration patterns. We've shown that otoliths also capture the signatures of contaminants that have affected the fish's ecosystems,” Brandt said.

The specific isotope that the team analyzed was strontium. According to Science Daily, strontium is unique in that it is a naturally occurring trace element in coal that retains isotopic ratios even after the coal is burned and coal ash is introduced to an aquatic environment.

The team was able to verify the origins of the coal ash because strontium isotope ratios in the otoliths of fish matched the strontium isotope ratios in samples collected from sediment at the bottom of the lakes. "This shows otoliths can be used as biogenic tracers to assess the potential for ecological impacts of coal ash waste streams in affected waters," said Brandt.

Coal ash is toxic to humans and wildlife. Photo: Tree Hugger

The potential of this new, surprising tool is vast. "This study's finding demonstrates that otolith studies can add to our existing research efforts," said Brandt. "Water-based strontium isotope tracers only give us information about coal ash impacts at a particular point in time, but because otoliths continuously grow over a fish's lifetime, we could use time-series analyses of otoliths to determine the timing of waste stream discharges or spills going back several years. This represents an emerging and important new direction in environmental toxicology and water-quality research."

Sources: Science Daily, Earth Justice, Environmental Science & Technology Letters

About the Author
  • Kathryn is a curious world-traveller interested in the intersection between nature, culture, history, and people. She has worked for environmental education non-profits and is a Spanish/English interpreter.
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