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