Marine biologists are shocked at the high levels of microplastic pollution in the ocean sediments of Australia's south-east coast, with Bicheno in Tasmania being the worst.
Scientists from the Institute for Marine and Antarctic Studies at the University of Tasmania studied maritime sediments at 42 locations from Adelaide to Sydney.
The areas sampled included Sydney Harbour, Jervis Bay, Eden, Port Philip Bay, Port Adelaide and the coast south of Adelaide, as well as Hobart's Derwent Estuary and Tasmania's east coast.
Marine biologist Dr Scott Ling said the huge volume of plastics in the ocean and on beaches had received global attention but microplastics on the seafloor had been largely overlooked.
He said studies had estimated 70 per cent of marine litter would sink to the seafloor and enter marine sediments.
The new study was among the first in Australia to examine the sedimentary problem, taking samples to a depth of 10 centimetres.
Researchers had expected to find high levels of pollution close to major capitals but were surprised to find similar concentrations far from urban centres.
"On average we found about 3.4 microplastics in every millilitre of sediment we sampled," Dr Ling said.