19 Aug 2020
Study suggests compounds used in the manufacture of plastics may have contributed to the deaths of dolphins washed up on beaches in the US.
John Bonner
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Image © PublicDomainImages / Pixabay
Vets in the US have found high concentrations of industrial pollutants in the blubber and liver tissue of dolphins washed up on beaches of the south‑eastern states of Florida and Georgia.
The chemicals included many compounds used in the manufacture of plastics that have not been previously reported in marine mammals, but are known to impair the health of laboratory rodents and may have contributed to the deaths of these dolphins.
Led by Annie Page-Karjian of Florida Atlantic University, the study has been published in the journal Frontiers in Marine Science and describes the findings in 83 odontocetes (toothed whales) that were stranded between 2012-18. They belonged to 11 different species of dolphins and small whales, although more than half were the familiar bottlenose dolphin.
What is unusual about this new study is the wide range of pollutants tested. These include various compounds used in manufacturing plastics that are also known to be endocrine disruptor compounds in rodents.
Further analyses detected metals such as cadmium and mercury; the herbicide atrazine; and triclosan, an antibacterial and antifungal agent used in skincare products and toothpaste.
Taken individually, it is unlikely the pollutants reach a sufficiently high concentration to cause mortality to marine mammals, but Dr Page-Karjian said the chronic effects of a combination of different pollutants should be of concern.
She said: “Sublethal cellular changes related to toxicant exposure in free-ranging odontocetes may lead to health declines and, in combination with other factors, may contribute to stranding.”
Francesca Bevan, chemical policy and advocacy manager at the Marine Conservation Society, said the US study has implications for environmental research this side of the Atlantic.
She said: “This study is important in furthering the understanding of contaminants that are being released into the environment and, ultimately, ending up in cetaceans.
“The presence of these chemical contaminants in the environment is making wildlife more vulnerable to other environmental stressors, which, in turn, is making them less resilient to the sublethal effects of these contaminants.
“It is extremely important that more of these studies are conducted, monitoring an even greater array of contaminants, to understand the true picture of chemical pollution and its effects in the marine environment.”
