he distribution of microplastics in polar regions is relatively unknown, but it is key to understanding the fate and potential impact of this pervasive and complex pollutant in these remote and threatened environments. This thesis focuses on the most accessible and arguably vital matrix in which microplastics may exist in the Arctic and Antarctic; the near-surface environments such as seawater and snow. Although likely to be transient, microplastics in these matrices present a direct interface between humans (the polluter) and the environment (the polluted). Determining distribution at the surface is vital to understanding the impact of an increasing human presence in these regions and an increasing human footprint via long-range transport. Three distinct environments have been explored in this thesis to provide data on the characteristics and concentrations of microplastics and facilitate the development of methods that enable perceived “pristine” environments to be effectively and rigorously investigated. In both the Canadian Arctic and the Southern Ocean, this thesis shows that microplastic concentrations are low compared with global concentrations. In the Arctic, it is shown that a 300 µm mesh, which has typically been used in marine microplastic research, retains only 6% of the particulate, which can be potentially captured on a 50 µm mesh, therefore significantly underestimating microplastic abundance and overlooking the characterisation of the most bioavailable size fraction to polar ecosystems.
In the Southern Ocean, although concentrations are low, it is demonstrated that these are significantly high enough for microplastics to be encountered and therefore potentially ingested by pelagic amphipods. With little known about the subsidiary impacts of microplastics on the biogeochemistry of other pollutants in the Southern Ocean, an experiment exploring the impact of microplastics on mercury uptake by Antarctic krill has been carried out. Results from this ship-based laboratory experiment indicate that virgin microplastics, compared to particulate organic matter, play an insignificant role in mercury uptake by Antarctic krill. As methods developed, the final environmental dataset collected in Antarctic snow was analysed using automated analysis, revealing remarkably high concentrations of the smallest microplastics, heterogeneously distributed in continental Antarctica. These findings provide valuable insight into the distribution and potential fate of microplastics in polar environments whilst also providing vital information on the methods of carrying out polar plastics research. In combination, this is key to providing an evidence base for needs and ways to monitor and understand the impact of microplastics in remote polar regions.