Microplastics revealed in New Zealand marine mammals for the first time

Friday 12 November 2021

Scientists have found microplastics in all New Zealand dolphins they examined, a new study has revealed.


Examples of small white, blue and translucent microplastics.

Last updated: Monday 28 November 2022

Scientists have found microplastics in all New Zealand dolphins they examined, a new study has revealed. The international team led by Massey University and the Institute of Environmental Science and Research (ESR) discovered that all common dolphins examined post-mortem during 2019 and 2020 had ingested microplastics.

The research findings just published in Marine Pollution Bulletin quantified size, morphology, colour and polymer type of all microplastics recovered from stomach contents of dolphins that had stranded around New Zealand. The study revealed polyethylene terephthalate as the most predominant polymer in fibres, whereas polypropylene and acrylonitrile butadiene styrene were more frequently recorded as fragments.

The study’s first author, Professor Karen Stockin, says, “We were surprised to discover most microplastics extracted from dolphins comprised fragments as opposed to fibres, which is contrary to most international studies of microplastics in marine mammals, although aligns with New Zealand freshwater sampling. “While this is the first study to record microplastics in any New Zealand marine apex predator, it’s not surprising that microplastics were ubiquitous, given the significant levels of microplastics that have recently been reported in New Zealand waterways and coastlines.”

There are multiple sources of microplastics, and macroplastics, which over time breakdown into microplastics, entering our near-shore coastal environments. Wastewater is one major source. Modern wastewater treatment plants are designed to capture and remove large debris from water during treatment processes, and remove microbial and some chemical contaminants, but not microplastics. This means that high levels of microplastics pass through the treatment process and are discharged into the environment. This has recently been demonstrated to occur in New Zealand. Given increasing concerns about the impacts of microplastics on wildlife and human health, Royal Society Te Apārangi and the Office of the Prime Minister’s Chief Science Advisor released a report titled Rethinking Plastics in Aotearoa New Zealand which outlined a timeline of plastic innovations to mitigate impacts. Internationally, studies have hypothesised that human exposure to microplastics could lead to oxidative stress, DNA damage and inflammation, and other health problems. It’s not only the plastic particles themselves that are potentially harmful either. The surface of microplastics in the environment are colonised by micro-organisms, some of which have been identified as human pathogens.

Ministry of Business, Innovation and Employment (MBIE) Endeavour-funded Aotearoa Impacts and Mitigation of Microplastics (AIM²) research co-lead Dr Olga Pantos says, “Microplastics have been found in all environments and species that have been tested, including in whales and dolphins in other parts of the world. It was therefore no surprise that we also found them in the stomachs of dolphins in New Zealand waters.”

Dr Pantos, the ESR lead on the current dolphin study, has recently completed a research expedition in Fiordland to examine the levels of microplastics in surface waters. “We did see some pieces of plastics in our samples that would be considered meso or macroplastics, so we are expecting to find microplastics when we process them in the lab. It was very confronting seeing these plastics and then within hours also seeing pods of humpback whales, including juveniles, feeding in the same area.”

Dr Gabriel Machovsky, a co-author on the dolphin study who also co-authored a second study published in Science early this year, states, “Over 1557 species are known to consume plastics worldwide. However, information on the type of species that consume macro and microplastics in the Southern Hemisphere is scarce compared to other parts of the world. Therefore, this study is the first step to better understand the extent of plastic pollution in marine environments and their trophic webs within New Zealand waters”.

What are microplastics?

Microplastics are small (less than five millimetre) plastic particles that have originated either from primary or secondary sources. Primary microplastics are manufactured for specific uses, for example, microbeads are used in personal care products such as facial cleansers, toothpaste, and cosmetics as well as industrial cleaning products. Secondary microplastics are plastics originating from the fragmentation of larger plastic items. Examples include fibres from synthetic clothing and fragments of items such as plastic bags and bottles. Both primary and secondary microplastics can be transported to freshwater and marine environments when they are washed into stormwater and wastewater systems. Plastic particles are also found in the air and can be transported long distances before they settle out through gravity or as a result of rainfall.