Transport, Fate, and Effects of Microplastics in a Rapidly Changing Arctic

Microplastics (<5 mm) have been deemed a contaminant of emerging Arctic concern. Microplastics are multi-dimensional in that they range in morphology, size, and chemical cocktail (e.g., additives, sorbed contaminants) and are hypothesized to serve as an important transport mechanism for chemical contaminants to and within northern ecosystems. While microplastics and plastic additives have been identified across Arctic ecosystems, there is a need to better understand the transport, fate, and effects of microplastics and their additive chemicals. Here, I explore these three themes through a series of field observations and laboratory experiments. First, in Chapter 2 of this dissertation, I show that while seabirds may be an important transport pathway of microplastics to the Arctic, there are other regional sources that need to be considered. In Chapters 3 and 4, I explored the role of long-range atmospheric transport of microplastics via atmospheric deposition. In Chapter 3, using a high-Arctic ice core, I show an increasing trend of microplastics over time. I also observed a positive relationship between microplastics and organophosphate esters (a plastic additive), suggesting microplastics may act as a long-range transport pathway. In Chapter 4, I sampled snow from five sites at increasing distances from a local community. I observed a change in microplastic and polymer composition in sites closer to the local community suggesting that local sources of microplastics may also be important. In Chapter 5, I investigated the presence of microplastics and additive chemicals in wild-caught Arctic char (Salvelinus alpinus) and their habitat. Here, I show elevated concentrations of microplastics in Arctic char and their summer feeding habitat compared to previously reported observations. I also demonstrate translocation of microplastics to Arctic char. And finally, in Chapter 6, informed by observations in the previous chapters, I exposed larval fish to polyurethane, with and without chemical additives to assess the mechanisms of toxicity. Here, I show that the physical and chemical components of polyurethane affect growth and development, and that the physical particles may facilitate the bioaccumulation of plastic additive chemicals. Throughout my thesis, I highlight the importance of evaluating microplastics as a multi-dimensional contaminant - the physical and chemical properties may influence their fate, transport, and biological effects.