Microplastic pollution in the Arctic Ocean: Assessing ingestion and potential health effects in Calanus and Neocalanus copepods

Microplastics (MPs; plastic particles 1 µm–5 mm) are an emerging contaminant in the world’s oceans; found from surface to seabed in many forms. Evidence for ingestion of MPs exists for a variety of organisms including zooplankton, bivalves, and fishes, raising concern about potential effects in marine food webs. Although studies have reported MPs in the remote Arctic Ocean, data are nonexistent on the ingestion and associated health effects in calanoid copepods (zooplankton). Copepod samples were collected at 56 stations along 10 transect lines spanning the Northeast Pacific and Arctic Oceans and digested according to a novel enzymatic method developed during this thesis. Using light microscopy, MPs were quantified and characterized in Calanus and Neocalanus copepods. Polymer identity was confirmed for each microparticle isolated using Fourier-transform infrared spectroscopy (FTIR). Microplastic ingestion was confirmed at 6 of the 12 Arctic sampling stations. Particle density (PD) ranged from 2.79–15.28 MPs per gram wet weight sample. Differences in PD among survey regions and sampling stations were not significant. RNA:DNA ratios were determined as an indicator of health (i.e., growth and condition) and a station-specific relative RNA:DNA index (RRD) was calculated to account for differences in temperature; both were examined in relation to MP ingestion in Calanus glacialis copepods. A positive trend was observed between station-specific PD and both RNA:DNA ratios and RRD; neither correlation was statistically significant (RNA:DNA ratios: rp = 0.52, p = 0.154; RRD: rp = 0.45, p = 0.220), however the strength of the relationship is notable. The results of this thesis confirm MP ingestion in copepods in the Arctic Ocean, and constitute the first examination of associated health effects in the keystone copepod of Arctic Ocean ecosystems.