Microplastics research reveals alarming pollution levels on Auckland beaches

Researchers at the University of Auckland have uncovered concerning levels of microplastic pollution in Auckland's coastal environment, shedding light on an invisible threat that poses a significant risk to marine ecosystems.

The study, published in Science of The Total Environment, indicated the widespread occurrence of microplastics in sand and seawater from Auckland beaches, with concentrations at least 50 times higher than previously reported in New Zealand coastlines.

Microplastics, tiny particles often invisible to the naked eye, have become a major environmental concern due to their enduring nature, widespread distribution and potential harm to wildlife and ecosystems.

The study was carried out from July to August 2022 at beaches in Westhaven, Herne Bay, Okahu Bay, Kohimarama, Saint Heliers and Mission Bay, and around Auckland Ferry Terminal.

Senior author, Associate Professor Lokesh Padhye from the Faculty of Engineering, says the results are alarming.

“Our results indicate that if we arranged all the pieces of detected microplastics side by side, it would result in one metre of plastic from just one kilogram of sand that we sampled. That’s astonishing,” he says.

“Additionally, a few microplastic particles per litre of seawater may not seem that big, but when you think about the number of litres of water that the open ocean contains, the magnitude of plastic pollution becomes clearer.”

Meticulous sampling and advanced imaging were key features of the study, which may help to explain why contamination levels were discovered to be significantly higher than previously reported, says Padhye.

The research team utilised advanced laser direct infrared imaging techniques to identify plastics, including polyethylene terephthalate (PET), nylon, polyurethane (PU) and polyethylene (PE), which are widely used in packaging, coatings, footwear and textiles.

“Once released into the ocean, microplastics accumulate within aquatic ecosystems, inflicting injuries, disrupting feeding patterns and triggering various harmful effects, including suffocation and diminished growth rates. Microplastics also interact with other contaminants, compounding their harmful effects and posing risks to ecological and human health.”

One noteworthy discovery from the study revealed a markedly elevated, approximately tenfold increase in the concentration of microplastics in the vicinity of stormwater outlets.

“This suggests a potential link between urban runoff and microplastic pollution in marine ecosystems. Stormwater drains on streets, sidewalks and other surfaces may serve as conduits for microplastics, contributing to higher contamination levels in coastal areas.”

The study, by lead author and Padhye’s PhD student, Mahyar Ghanadi, calls for effective stormwater management and waste reduction strategies to mitigate microplastic pollution in Auckland's coastal regions.

“Our findings underscore the urgency of addressing microplastic pollution to safeguard marine ecosystems. Continuous monitoring is crucial for a comprehensive understanding of the sources, fate and transport of microplastics in marine environments,” says Ghanadi.

A positive outcome highlighted in the research was the reduced presence of polyethylene around Auckland beaches, possibly attributable to the regulations on single-use plastic shopping bags implemented in New Zealand since July 2019.

“This provides optimism about the effectiveness of environmentally friendly policy shifts in tackling such global challenges,” says Padhye.