Queensland Alliance for Environmental Health Services researcher and study lead author C Alex Villa used turtles from the Howick Group of islands in the state’s far north, which are typically removed from localised human-caused pollution, as a baseline to compare turtles from Cleveland Bay, Upstart Bay and Shoalwater Bay.
Villa said while the Cleveland Bay and Upstart Bay turtles looked healthy on the outside their blood cobalt levels were very high in comparison to the set baseline levels, with Upstart Bay turtles showing cobalt blood levels four to 25 times higher.
Levels of other metals well above the baseline were also detected in the blood including molybdenum, manganese, magnesium, sodium, arsenic, antimony and lead.
Cobalt is a naturally occurring mineral but it can also be an environmental pollutant, and environmental levels can be increased well beyond normal if released by industrial, agricultural or other human activities.
The source of this metal exposure is not known, however.
Queensland is a major exporter of cobalt, as well as copper and nickel ores.
University of Queensland environmental veterinarian and study co-author Dr Mark Flint said 44% of tested Upstart Bay turtles indicated signs of a systematic stressor and an active inflammatory response.
Additionally, elevated levels of cobalt, antimony and manganese correlated with clinical markers of inflammation, and markers indicating stress on turtle organs needed for expelling toxins, with a quarter of the 161 turtles examined at Upstart Bay having mild to severe eye lesions.
“We don’t know why this is occurring,” he said.
“The infection appears to be bacterial and not a virus, so it could be another indication that this is a population under pressure.”
Co-author Dr Caroline Gaus, who found last year that green turtles from Queensland’s nearshore habitats were exposed to thousands of chemicals, said the recent findings supported the notion metal exposure was impacting the health of coastal populations of sea turtles, but the exact effects and extent required closer examination.
The study was a partnership between QAEHS, UQ School of Veterinary Science’s Vet-MARTI unit, World Wildlife Fund-Australia, the Queensland Department of Environment and Heritage Protection, Griffith University, and James Cook University with support from the Great Barrier Reef Marine Park Authority, and funding from Banrock Station Environmental Trust.
