Quantification of plankton-sized microplastics in a productive coastal Arctic marine ecosystem

Abstract

Microplastics (MPs) are polluting the Arctic, but our understanding of their abundance, distribution, andsources is limited. This study quantified MPs down to 10mm in marine waters of the most populatedregion in Greenland. A new plastic-free pump-filter system was used to collect MPs from surface watersin the fjord Nuup Kangerlua close to Nuuk. Additionally, we took samples by horizontal tows with abongo net (300mm mesh-size). The median concentrations were 142 MPs m 3and 0.12 MPs m 3in thepump and bongo samples, respectively. The most abundant polymer was polyester across stations andsampling types. Fibers were the dominant shape in the bongo samples, while non-fibrous particlesdominated in the pump samples. MP abundance was lower in the fjord and increased close to Nuuk andtowards the open ocean, indicating that Nuuk is an important point source for MPs. In both samples,concentrations of MPs increased with decreasing size, illustrating the importance of quantifying thesmallest fraction of MPs. Thus, the use of methods allowing for a quantification of the smallest MPs isvital to reduce the underestimation of MP concentrations in the environment. The smallest size fractionis also most available to plankton-feeding marine invertebrates and an important entry point for MPsinto marine food webs. At the found concentrations, immediate adverse effects on the pelagic food websare unlikely. However, growing anthropogenic activities could increase the risk of MPs to affect thesensitive Arctic ecosystem.