Abstract
The abundance and distribution of microplastics within 5 sediment size classes (>5000 μm, 1000–5000 μm, 250–1000 μm, 250–0.63 μm and < 0.63 μm) were determined for 16 sites within Lambert Channel and Baynes Sound, British Columbia, Canada. This region is Canada’s premier growing area for the Pacific oyster (Crassostrea gigas). Microplastics were found at all sampling locations indicating widespread contamination of this region with these particles. Three types of microplastics were recovered: microbeads, which occurred in the greatest number (up to 25000/kg dry sediment) and microfibers and microfragments, which were much less in number compared with microbeads and occurred in similar amounts (100–300/kg dry sediment). Microbeads were recovered primarily in the < 0.63 μm and 250–0.63 μm sediment size class, whereas microfragments and microfibers were generally identified in all 5 sediment size classes. Abundance and distribution of the three types of microplastics were spatially dependent with principal component analysis (PCA) indicating that 84 percent of the variation in abundance and distribution was due to the presence of high numbers of microbeads at three locations within the study region. At these sites, microbeads expressed as a percent component of the sediment by weight was similar to key geochemical components that govern trace metal behavior and availability to benthic organisms. Microbeads have been shown to accumulate metals from the aquatic environment, hence in addition to the traditional geochemical components such as silt and organic matter, microplastics also need to be considered as a sediment component that can influence trace metal geochemistry. Our findings have shown that BC’s premier oyster growing region is highly contaminated with microplastics, notably microbeads. It would be prudent to assess the degree to which oysters from this region are ingesting microplastics. If so, it would have direct implications for Canada’s oyster farming industry with respect to the health of the oyster and the quality of product that is being farmed and sets an example for other shellfish growing regions of the world.
Highlights
Microplastics have been defined as plastic particles 5 mm in length [1, 2, 3, 4] and depending on their origin, can be divided into two groups: primary, virgin granules originally constructed to be of microscopic size and used to produce macroplastics and secondary, originating from the degradation of macroplastics [5]
While we know much about the abundance and distribution of microplastics as defined by those plastics < 5 mm in size [e.g. 17, 18], less is known about how different microplastics behave within marine sedimentary environments, the abundance and distribution of different types of microplastics
Unknown is how important microplastics are as compared to traditional sediment components such as percent weight of organic matter and silt, key determinants for the fate of metals within sedimentary environments
Summary
Microplastics have been defined as plastic particles 5 mm in length [1, 2, 3, 4] and depending on their origin, can be divided into two groups: primary, virgin granules originally constructed to be of microscopic size and used to produce macroplastics and secondary, originating from the degradation of macroplastics [5]. Nine types of polymers have been identified in intertidal sediments: acrylic, alkyd, polyethylene, polypropylene, polyamide (nylon), polyester, polymethyl acrylate, and polyvinyl-alcohol [4, 15]. These have a wide range of uses, including clothing, packaging, rope, basic household items, personal care products, agriculture and industry. Zhang et al [16] recently reviewed the literature on the effects of sediment geochemical properties on heavy metal bioavailability and noted that under anoxic conditions, acid-volatile sulfides reduce solubility and toxicity of metals, whereas oxides and iron and manganese, organic matter, clay and silt can stabilize metals in oxic environments
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