A pilot study to determine the potential impacts of plastics on Aotearoa-New Zealand’s marine environment

, Pantos Olga, Audrezet Francois, Doake Fraser, Donaldson Lloyd, Dupont Pierre, Gaw Sally, Kingsbury Joanne, Weaver Louise, Lear Gavin, Northcott Grant, Pochon Xavier, Smith Dawn, Theobald Beatrix, Wallbank Jessica, Zaiko Anastasija, Maday Stefan.

Once in the ocean, plastics are rapidly colonised by complex communities. Due to the buoyant and resilient nature, ocean plastics pose a significant risk to ecosystems and fishery-based economies through their role in the translocation of invasive species and pathogens or changes in ecosystem function. Factors affecting the development and composition of these communities are still poorly understood, and there is currently no information on the biofilms that form on marine plastics in the southern hemisphere or their potential risks to the environment. This study aims to address this knowledge gap. To do this, two chemically and structurally distinct polymers, which are also common in marine plastic litter, nylon 6 and polyethylene, were deployed for 3-months in the Port of Lyttelton, Christchurch, New Zealand. Biofilm present after 2 weeks was dominated by diatoms and cyanobacteria. Metagenomic analysis showed that the plastisphere was distinct from the communities associated with glass control surfaces and the surrounding water. Polymer-specificity of the bacterial communities seen at 2-weeks was absent in subsequent time points, whereas fungal communities did not change over time. Although mechanical properties of the plastics did not change over time, physical modification to the surface of the plastics was observed, with the most pronounced change seen in nylon, with pitting conforming to the shape of microbial cells. This is the first study to examine the microbial communities associated with marine plastics in New Zealand waters, allowing the improvement of the understanding of the potential risk they pose. A year-long study is now underway to examine the fate of 5 plastic types, the plastisphere that develops, the presence of invasive species and potential pathogens, and plastic degrading microbes which may present bioremediation potential, as well as changes to the mechanical properties and inherent and acquired chemicals associated with the plastics.

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