A three-year study of plastic waste in the central Great Barrier Reef World Heritage Area has found there is a chronic risk to marine organisms from plastic exposure.
James Cook University’s Professor Mark Hamann and AIMS@JCU PhD candidate Michaela Miller were part of the study led by Dr Cherie Motti at the Australian Institute of Marine Science (AIMS).
Hamann said plastic pollution is found throughout the global marine environment, including seawater, marine sediment, ice cores, and a multitude of organisms at every depth.
“We estimate that by 2030 there will be a yearly input of between 20 and 53 million metric tonnes of plastic into aquatic eco-systems, with the associated risks likely to increase by roughly 50 per cent in some marine environments,” Hamann said.
He said microplastics less than five millimetres in size are a particular concern, due to their intake by marine organisms, which is often unintentional. Of greater concern is the retention of these microplastics in their guts.
The team, based at AIMS, conducted 66 surface seawater tows adjacent the SS Yongala shipwreck site, southeast of Townsville (Gurumbilbarra) between September 2016 and September 2019.
Miller analysed these samples and found 92 per cent of micro-sized fragments and fibres to be microplastics.
“We found a total of 533 microplastics in the 66 tows, with only one tow having none,” she said.
“Similar to our results, most microplastics previously detected in both the Great Barrier Reef waters and coral reef fishes have been identified as microfibres of textile origin, likely derived from clothing and furnishings.”
The team found microplastic concentrations were significantly influenced by extreme weather events and associated increases in wind speed and river discharges, resulting in an outflow of plastic debris from rivers.
“Despite peaking immediately following extreme weather events, the overall trend of plastic contamination did not change over the three years of study, suggesting continued and chronic risks of plastic exposure to marine organisms,” Miller said.
AIMS is using the findings of this study to develop a long-term marine microplastics monitoring program.
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