A pilot study to determine the potential impacts of plastics on Aotearoa-New Zealand's marine environment Olga Pantos∗1, Francois Audrezet2, Fraser Doake1, Lloyd Donaldson3, Pierre Dupont1, Sally Gaw4, Joanne Kingsbury1, Louise Weaver1, Gavin Lear5, Grant Northcott6, Xavier Pochon2,5, Dawn Smith3, Beatrix Theobald3, Jessica Wallbank5, Anastasija Zaiko2,5, and Stefan Maday5 1The Institute of Environmental Science and Research { Christchurch, New Zealand 2Cawthron Institute { Nelson, New Zealand 3Scion { Rotorua, New Zealand 4The University of Canterbury { Christchurch, New Zealand 5University of Auckland [Auckland] { New Zealand 6Northcott Research Consultants Ltd { Hamilton, New Zealand Abstract 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 com- munities 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 modi- fication 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 plas- tics 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. ∗Speaker sciencesconf.org:micro2020:334094 Keywords: marine plastics, plastisphere, polyethylene, nylon, Southern Hemisphere.