Investigating the sources, transfer, and fate of microplastics in the Arctic marine environment

Contamination of the world’s oceans by plastic waste continues to be a widespread global concern, with microplastics posing a particular threat due to their ability to be transported globally and ingested by a wider range of marine biota. In the Arctic, microplastics have now been reported in sea ice, snow, surface and sub-surface waters and deep-sea sediment, as well as Arctic biota, but large parts of the Arctic have not been subject to monitoring. In addition, scientific appraisals into the sources, cycling and fate of microplastics reveal multiple knowledge gaps, including the effects of these pollutants on Arctic ecosystems. This thesis provides new insights into the occurrence of microplastics particles in the Beaufort Sea where particles were found at much higher concentrations than other areas of the Arctic. These high concentrations may also be found in sea ice, with results showing sea ice formation led to the incorporation of microplastic particles from seawater with very high concentrations in the uppermost layer of ice (ice - atmosphere interface), reinforcing the notion that sea ice can act as a significant ‘temporary’ sink for microplastic pollution. This raises concerns for Arctic biota, however results showed zooplankton species C. finmarchicus contained very low microplastic concentrations, suggesting they are unlikely to be acting as a transfer mechanism for microplastics from surface waters to the deep ocean. Overall, the results from this study suggest future research should focus on assessing potential sinks for microplastic pollution in the Arctic, as well as the effects of microplastic ingestion in sympagic (ice-associated) organisms.