Survey of microplastics in a freshwater and saltwater ecosystem

Abstract

The objective of our study was to quantify the abundance of microplastics across a salmon migration gradient, using a freshwater and seawater site as proxies for the habitats that salmon encounter along their migration route. Three 190L water samples were filtered using a plankton net at two different sites in the city of Vancouver: the mouth of Salish Creek, and the waters off Jericho Beach. Samples were treated using Proteinase-K digestion and microplastics were visually identified using Zeiss Axiostar compound microscopes and a microplastic identification key. An unpaired two-tailed t-test returned a t-value of 2.4010 and a p-value of 0.0743. Although the results are not statistically significant (p-value < 0.05), we did find a trend showing that the ocean samples contained a larger quantity of microplastic fragments. The presence of microplastic fragments in both the freshwater and ocean water samples is alarming since microplastics have been known to inflict negative effects on fish physiology and behaviour. This is especially alarming for the restoration of habitats for Pacific salmonids as microplastics in the freshwater streams may harm juveniles and returning spawners.