WELLINGTON (XINHUA) - A pilot study carried out by New Zealand's National Institute of Water and Atmospheric Research (Niwa) and the University of Auckland has found microplastics in samples collected from the seabed in New Zealand's Marlborough Sounds, Niwa said in a statement on Friday (July 16).

A global problem, microplastics have been found across the planet, including in alpine soils, Antarctic waters and at the bottom of oceanic trenches, thousands of metres below the sea surface.

Microplastics are defined as pieces of plastic less than 5mm long and are either manufactured to be small or derived from larger plastics that have broken down into smaller pieces.

Niwa marine geologist Sally Watson co-led the study with University of Auckland's Dr Marta Riba and Dr Lorna Strachan.

In July 2020, several sediment cores were collected by Niwa research vessel Ikatere from Long Island - Kokomohua Marine Reserve, near the mouth of the Queen Charlotte Sound, 30km from Picton.

The samples were collected by a corer that extracts sediment up to 1m into the seafloor in waters 30m to 70m deep.

Dr Watson and Dr Riba processed the samples in a laboratory by mixing them with a chemical solution and filtering them to extract the micro-sized plastic particles.

Analysis found microplastic pellets, fragments and fibres, coloured blue, black, white, and red in the samples.

"We didn't expect to see such a range of different microplastics quite far away from an urban area," Dr Watson said.

Further analysis will be needed to determine where the microplastics may have come from, but Dr Watson said potential sources could include paint chips from boats, monofilament fishing line and microfibre from clothes.

Recent studies by Niwa and Auckland University found microplastics in the guts and muscle tissue of several species of fish caught in the Hauraki Gulf.

Dr Watson said that animals feed on sea floor sediments, and microplastics are understood to move up marine food chains. Nanoplastic particles (1,000 times smaller than microplastics) can pass through cell membranes into living tissue, although further research into the impact of nanoplastic is required.

Dr Watson said the next steps for the research will be to determine what items the microplastics are coming from, analysing further sediment cores from the area to determine how widespread the problem is and understanding how deep microplastics are in the seafloor.

Between 60 per cent and 90 per cent of the litter that accumulates on shorelines, the surface and the seafloor is made up of plastic. Each year, an estimated eight million tonnes of plastic end up in the ocean, equivalent to a full garbage truck dumped into the sea every minute, according to a report by the United Nations Environment Programme (Unep).

The Unep launched Clean Seas Campaign in 2017 to push global efforts to tackle single-use plastics and microbeads.