Number of plastic microbeads (a) and microfiber and microfragments (b) recovered from the intertidal sediments from the 16 sampling locations within Baynes Sound and Lambert Channel, Canada. Graphic: Kazmiruk, et al., 2018 / PLOS ONE

23 May 2018 (SFU) – British Columbia’s premier shellfish farming region is heavily contaminated with microplastics, according to a new SFU study.

New research from SFU’s Ecotoxicology Research Group shows Lambert Channel and Baynes Sound off Denman Island are awash with microbeads and other microplastics including fragments and fibres.

The area is also home to approximately 130 shellfish farms – which is part of the problem and a health concern says lead author Leah Bendell, a professor of marine ecology and ecotoxicology at SFU.

Using a technique developed by co-author and PhD candidate Tamara Kazmiruk, the team analyzed dozens of sediment samples taken from 16 different sites around the island to ascertain the presence of microplastics.

A painstaking process of drying and characterizing tiny bits of sediment that was later sieved, treated and then filtered through a glass microfibre filter by vacuum filtration was used to divide organic from non-organic materials.

“We found microbeads in the smallest bits of sediment and in a concentration equal to the amounts of silt and organic matter,” Bendell says.

Microbeads are an unwelcome presence because they also absorb trace metals. Bendell explains that plastics accumulate trace metals making them a potential source of toxic metals to intertidal food webs.

Bendell has been studying the area for almost 20 years and reports that since 2006 when the island community began their yearly beach cleanup, each year, three to five tonnes of debris, comprised primarily of plastic materials are recovered from the intertidal regions of Baynes Sound.

“While there is also contamination from urban sources, 90 per cent of these plastics can be attributed to shellfish farms,” Bendell says.

Her research confirms that sites where the greatest number of micro fragments and microfibres were found where also in regions of extensive shellfish aquaculture equipment.

Bendell points out that the shellfish industry makes extensive use of High Density Polyethylene (HDPE), in the form of netting, oyster bags, trays, cages, and fences which makes up a large amount of the recovered plastic.

Previous studies have shown that oyster reproduction and overall health has been adversely affected by exposure to polystyrene microplastics because it interferes with their energy uptake and allocation, reproduction and overall performance.

As for consumption of these shellfish by humans and organisms in the food chain, Bendell says that it would be prudent to investigate.

Finally, Bendell notes this is also an industry challenged by climate change, ocean acidification and increased incidences of shellfish borne diseases.

“It is not business as usual and the governments responsible should be providing direction to the industry on how to adapt to a changing environment. Existing practices are not going to work in the long run.”

The region around Denman Island has been designated by the Department of Fisheries as an Ecologically Biologically Sensitive Area (EBSA). It provides a critical habitat for migratory birds and its waterways offer an important marine pathway for orcas.

Bendell is adamant that while microbeads and plastics seriously impact the environment, it is within our ability to take action.

“There should be zero tolerance for plastics in our aquatic systems. We can take responsibility for some of those plastics but the shellfish industry has to get onboard and recognize that this is a very serious problem that has to be addressed.”

The study was published today in PLOS One.

Prime growing areas for B.C. oysters contain alarmingly high concentrations of plastic microbeads

Examples of the types of microplastics recovered from sediments of a key shellfish growing region of Canada, Lambert Channel and Baynes Sound, British Columbia. Photo: Kazmiruk, et al., 2018 / PLOS ONE

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.

Abundance and distribution of microplastics within surface sediments of a key shellfish growing region of Canada



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