http://www.nrcresearchpress.com/doi/abs/10.1139/cjfas-2014-0281

Rowshyra A. Castañeda, Suncica Avlijas, M. Anouk Simard, Anthony Ricciardi
Microplastic pollution in St. Lawrence River sediments
Canadian Journal of Fisheries and Aquatic Sciences, Published on the web
3 September 2014, 10.1139/cjfas-2014-0281

ABSTRACT
Although widely detected in marine ecosystems, microplastic pollution
has only recently been documented in freshwater environments, almost
exclusively in surface waters. Here, we report microplastics
(polyethylene microbeads, 0.40?2.16 mm diameter) in the sediments of the
St. Lawrence River. We sampled 10 freshwater sites along a 320 km
section from Lake St. Francis to Québec City by passing sediment
collected from a benthic grab through a 500 ?m sieve. Microbeads were
discovered throughout this section, and their abundances varied by four
orders of magnitude across sites. Median and mean (±1 SE) densities
across sites were 52 microbeads·m?2 and 13?832 (±13?677) microbeads·m?2,
respectively. The highest site density was 1.4 × 105 microbeads·m?2 (or
103 microbeads·L?1), which is similar in magnitude to microplastic
concentrations found in the world?s most contaminated marine sediments.
Mean diameter of microbeads was smaller at sites receiving municipal or
industrial effluent (0.70 ± 0.01 mm) than at non-effluent sites (0.98 ±
0.01 mm), perhaps suggesting differential origins. Given the prevalence
and locally high densities of microplastics in St. Lawrence River
sediments, their ingestion by benthivorous fishes and macroinvertebrates
warrants investigation.

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