Microplastics are tiny particles of plastic 0.1 to 5mm in size. They can be primary plastic particles made for purpose, or secondary particles fragmented from larger plastic items. There is estimated to be more than 15 trillion pieces of microplastic debris in the world’s oceans, 80 percent originating from land-based activities.

ESR scientists have been part of AIM² - Aotearoa Impacts and Mitigation of Microplastic - the first national research programme to investigate the impact of microplastics on Aotearoa New Zealand. 

Led by ESR’s Dr Olga Pantos and Dr Grant Northcott from Northcott Research Consultants Ltd, AIM² brought together experts from six research institutes and universities, to improve the knowledge and understanding of the level and movement of microplastic pollution in freshwater, marine and terrestrial environments in Aotearoa. They also assessed the risk they pose to organisms and ecosystems and the knock-on effects to our nature-based economy and wellbeing. 

The MBIE Endeavour Funded programme concluded in March 2024, adding a wealth of knowledge about microplastics in Aotearoa.

The type of plastic and the way it interacts with the environment can impact ecosystems and animal health. To understand what is in our marine environment, sea surface and beach sands, researchers ran experiments at different coastal locations around the country to examine the interactions with the marine environment.

In 2020 five different plastics were deployed in coastal waters around Aotearoa, at marine sites in Auckland, Nelson and Christchurch. Held in place by large steel frames, the researchers left the plastics in the sea for a year to see what started living on their surface and what chemicals were released or became associated with them.

Once in the marine environment plastics quickly become colonised by microbial communities, followed by a wide variety of invertebrates and seaweed, until a climax community forms. These communities can be home to invasive species or pathogens of concern, due to the negative effects they can have on the native species.

The researchers monitored the communities over time, using next-generation DNA sequencing methods. They also looked at how they affected the plastics themselves. For example, do the things that grow on them assist with their breakdown and the formation of microplastics?

The five plastics used in the experiment were a mixture of new and artificially aged and included two commonly found in plastic bags (polyethylene and oxo-polyethylene, the latter now banned in New Zealand), one commonly found in drink bottles (polyethylene terephthalate), one increasingly being used in food and liquid containers as a “sustainable” substitute for traditional plastics due to its compostability (polylactic acid), and one used in materials such as fishing lines (nylon). Although polylactic acid (PLA) is an industrially compostable plastic, the conditions required cannot be found in the ocean.

By studying the changes to the plastics over time, and the chemicals and organisms that become associated with them, the researchers can better understand the risks they may pose the environment. And by using artificially aged plastics they can assess how the risks and/or impacts the plastics pose the environment can change as the plastics weather. This is important as we know that there are plastics in the oceans that are just days old, as well as some that are five or six decades old. Only looking at the effects of new plastics does not tell us the full story.

Watch how research in Lyttelton Harbour is helping us understand what happens to plastics in sea water - and what this means for our ecosystems.

Researchers including ESR scientists, with help from the Sustainable Coastlines and Litter Intelligence projects, analysed beached plastic debris from 27 sites spanning the length of Aotearoa. The researchers are investigated which chemicals they contained, whether these chemicals were inherent in the plastic or acquired from the environment, and how much of these chemicals were released when they’re ingested by marine organisms.

Results have shown elevated concentrations of many toxic trace elements, such as cadmium and lead. These have been linked with the inorganic pigments used to give plastics their colour and therefore intentionally added (inherent). By simulating the conditions of marine organisms’ gastric fluid, the researchers have also shown that trace elements are released upon ingestion, which demonstrates the exposure of plastic-associated trace elements to organisms.

With a significant amount of plastic pollution entering the environment in urban settings and making its way to the oceans through freshwater channels (rivers, creeks and stormwater) it is important to understand the transition from human use to pollution, and how it affects the plastics’ fate and impact on the environment.

Just like the analysis of marine environments, ESR researchers and collaborators undertook projects that examined plastic at different stages of the freshwater plastic pollution journey. They looked at how microplastics act as a direct chemical contaminant source, absorb contaminants and make them bioavailable, and the microbial interactions involved in these processes.

Read more about the microplastic analyses and impact assessment carried out: Plastics and Te Wai Whau, Tāmaki Makaurau-Auckand.

Metropolitan urban

The Whau River catchment is in Auckland, Aotearoa New Zealand's largest city. The catchment includes urban and industrial areas and contains some of Auckland’s highest levels of pollution from urban stormwater, commercial/industrial site runoff, combined sewage overflows and litter.

Te Hau o te Whau (the essence of the Whau) is a pollution and waste-focused project that brings together groups working across science, community and iwi to help improve the mauri (life force) of the Whau River. 

Ecotoxicology and ecological effects

Little is known about the impact of microplastics on dry land. A PhD project by Helena Ruffell within the AIM² research programme explored the impacts of microplastics in productive soils. The project investigated sources of microplastics to the terrestrial environment, focusing on the beneficial reuse of biowastes (effluent, biosolids, compost, vermicast) and their application on to land.

A method was developed to extract microplastics from these mediums, enabling microplastics to be extracted from samples of these different biowastes collected from all around Aotearoa. The impact of microplastic contaminated soil on plant growth was also assessed, with a pot trial of mustard and ryegrass, with oxidative stress biomarkers and nutrient uptake analysed.

Wastewater

Wastewater treatment plants represent a major source of plastics into the environment, as a result of items that are flushed or find their way into this system. Research at the Christchurch wastewater treatment plant by students on the AIM² programme provided an opportunity to examine the impact of this. Their research established a relationship between different plastics and the chemicals and microbes in the wastewater, helping us to better understand the risks microplastics from our wastewater may pose for the environment.

ESR researchers have travelled to some of Aotearoa's most pristine spots to gather data about the scale and spread of microplastic pollution.

In 2021 ESR microplastics researchers Dr Olga Pantos and Hayden Masterton travelled to Northland as part of a research voyage bringing together two national collaborative research programmes - the AIM² (Aotearoa Impacts and Mitigation of Microplastics) project and the Marine Biosecurity Toolbox(external link) programme. Scientists from each programme are gathering data about microplastics pollution and assessing the prevalence of invasive pests in New Zealand’s coastal waters.

Collaboration and data sharing between the two projects is key, as plastic can act as a raft for invasive species to arrive in the waters around Aotearoa. Scientists across the two projects are working to identify which organisms tend to interact with different kinds of plastic so that they can make predictions about the threats the marine environment might face. During the voyage, Olga and Hayden collected over 100 water samples to analyse for the presence of microplastics at ESR’s Christchurch Science Centre, as well as delivering ocean literacy outreach work with schools and communities.

In the same year, the researchers also travelled to remote Fiordland to gather more data in some of New Zealand’s most pristine waters, and to consolidate knowledge about the extent of microplastic pollution. 

ESR’s Dr Olga Pantos and Dr Grant Northcott from Northcott Research Consultants Ltd lead the national research programme Aotearoa Impacts and Mitigation of Microplastics (AIM²).  

Dr Olga Pantos is a marine microbial ecologist. Since completing her degree in marine and environmental biology she has studied the impacts of anthropogenic (human caused) stressors on marine ecosystems. She was a panel member of the PM’s Chief Science Advisor’s Rethinking Plastics project and on the scientific advisory panel for the UNEA’s Marine Litter and Microplastics Expert Group.

Within the AIM² project her research focus is in determining the levels of microplastics in different ecosystems, and the interactions and impacts of these microplastics on microbial communities which are critical to the health and function of all ecosystems.

Dr Grant Northcott is an environmental analytical chemist with expertise on the fate and effects of organic contaminants in the environment. He leads the contaminant chemistry research within the AIM² project, examining the interactions between the plastic polymers and inherent and acquired chemical contaminants which play a critical role in the risk the plastic poses to the environment. 

The research team includes students from the Universities of Auckland and Canterbury. They are looking for the chemical contaminants that become associated with the plastics in the environment, and/or that are released into the environment, the microbes’ ability to fully degrade the plastics, plastics in soils, their sources and impacts on soil health, the effects of plastics on marine biosecurity, plastics in freshwater systems, and potential impacts on the ecology, and the ecotoxicological effects of plastics and their associated chemicals, inherent or acquired.