Microplastic particles less than 5mm in size were found in coastal sediments as part of a study that looked at 11 locations in Northland. Photo / David Pereiras
Microplastic particles less than 5mm in size were found in coastal sediments as part of a study that looked at 11 locations in Northland. Photo / David Pereiras
Some of Northland’s most pristine beaches are carrying the weight of a global pollution problem.
A new study has confirmed the presence of microplastics at 11 locations sampled, with Mangawhai recording the highest levels.
While levels varied between sites, researchers said the overall contamination was broadly similar across the region.Mangawhai, Sandy Bay and Omamari were among the locations showing the highest concentrations of large microplastic particles.
The study, carried out by Scion as part of a wide programme led by the Institute of Environmental Science and Research, aimed to quantify microplastics in beach sediment. Researchers looked at two particle sizes: large microplastics (0.3 to 5mm) and smaller ones (under 0.3mm).
Mangawhai had the highest levels of larger microplastics at 6.3 particles per kilogram of sediment, followed by Sandy Bay, Omamari and Waipū Cove. Taharoa and Onerahi had the lowest levels.
Overall, Northland’s average (3.1 particles per kg) was similar to that of other regions.
“The source of microplastic pollution in Northland beaches is likely to be very broad. Some originate from larger pieces of plastic debris which are broken down locally through environmental effects (sunlight, temperature, mechanical abrasion from sand etc.), while others will have been transported from sources farther away via marine and oceanic current,” the researchers said.
The research team behind the recent study into microplastics on Northland beaches.
“It is very challenging to distinguish and quantify the contributions of each source. The high proportion of fragments detected in the Northland samples [60% of all larger microplastics] compared to the Waikato and Canterbury, with their chemical composition [polyethylene and polypropylene dominating], hints at packaging or other rigid articles – as opposed to fibres – as a major source of microplastics contamination in Northland.”
Sediment samples were collected in collaboration with Northland Regional Council (NRC), and NRC coastal resource scientist Richard Griffiths said plastic litter was one of the biggest pollutants of the ocean.
“A major concern is the persistence of plastic pollution in the environment and that larger plastic items break down into smaller pieces [called microplastics] over time, which are mistaken for food items and are consumed by marine organisms. Once plastic is in the marine environment it is difficult and expensive to remove. There is also a potential human health risk from eating fish or shellfish containing microplastic.”
He said the biggest concern was the microplastics found in shellfish samples collected at Waipū and Mangawhai, as it could be a potential risk to human health.
Scientists extracted microplastics from the sand of 22 beaches from the Far North to Banks Peninsula.
“We do monitor litter and plastic regularly at two sites in Whangārei Harbour. We estimate that 13 million litter items are discharged from urban stormwater drains in Northland every year and that over 70% of the litter items are made of plastic.”
The Department of Conservation (DoC) said it was concerned about the spread of microplastics in marine environments, including the Far North.
While DoC was not directly involved in the recent study, marine species manager Malene Felsing said the findings raise red flags for local biodiversity.
“These tiny particles can accumulate in the food chain, affect water quality, and degrade sensitive habitats. Mangawhai and other parts of Northland are home to significant coastal and estuarine ecosystems, so findings like these are certainly concerning from a conservation perspective.”
She said microplastics are a growing issue in marine and coastal environments across Northland and the rest of the country.
Felsing added that while microplastics are a relatively new area of concern, they work alongside other agencies and researchers to build knowledge that is integrated into their management responses.
“Northland is home to many vulnerable coastal and marine species, including threatened seabirds like the tara iti [New Zealand fairy tern] and various native fish and invertebrate species found in estuaries and sandy shores.
“These ecosystems can be particularly sensitive to pollution, including microplastics, because of the way small particles accumulate in sediment and are ingested by filter-feeding organisms and small fish.”
