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Microplastics in Atlantic Canadian Waters

COINAtlantic is working with researchers at the University of New Brunswick on a new project, Microplastic Contamination in Coastal Regions of Southern Gulf of Saint Lawrence.

This is an introduction and more results will be shared as the project progresses.

Why do we rely so heavily on plastic? At a relatively low production cost, it offers a lightweight, airtight, waterproof, shatter resistant, corrosion resistant solution to an endless array of consumer needs. These properties that make plastic so incredibly versatile are the same properties that have led to it being listed as a ‘contaminant of emerging concern’ (CEC). A CEC is a broad classification that describes anything that is not currently monitored but has shown the potential to cause harm to either human health or the environment. The general nature of a CEC classification speaks to either a lack of scientific research or knowledge gaps in that research that makes it difficult to make any solid conclusion.

For plastic, one of those knowledge gaps lies in the amount of time it takes for plastic to completely degrade. What we do know is that over time, plastic debris in the environment breaks up into smaller and smaller pieces called microplastics - a term for particles smaller than 5 mm. Larger plastics become microplastics primarily through a combination of photo, thermal, and mechanical forces depending on the type of plastic and the environmental conditions in which the plastic has been deposited. Consider plastic in the marine environment. At a certain depth there is no light, so photodegradation is not possible, nor is thermal degradation if the water is cold. Mechanical forces can also be reduced at depth. Basically, this plastic can be hanging out in its original state, causing trouble for a very long time. In contrast, plastics can breakdown faster in surface waters, shallower coastal waters and shorelines where exposure to these degrading forces are much higher.

In an effort to understand this CEC from an Atlantic Canadian perspective, work began in 2017 in the Bay of Fundy which lies between the provinces of Nova Scotia and New Brunswick and touches the U.S. state of Maine. It is known for extremely powerful, semidiurnal tides that can reach up to 16 metres. This extreme tidal activity coupled with sun exposure on extensive tidal flats may increase the rate of plastic degradation. These important coastal habitats are critical for a variety of benthic invertebrates and are an important feeding area for coastal mammals and both local and migratory shorebird populations. These habitats are also critical to local fish populations who feed in these waters when the tide is high.

Marine and coastal wildlife often mistake plastic and microplastics for their intended food source. If the animal is unable to pass the plastic through its digestive system, it acts as a barrier to further nutrient absorption and a condition called pseudo-satiety. With the animal unable to fit additional food in their belly, and the stomach is either not emptying or emptying at a reduced rate, the animal will die. The ingestion of microplastics and the damaged caused is not limited to a single individual. Once the plastic has caused the death of an individual, that individual begins to decay (or is consumed by a larger animal) releasing the plastic back into the environment where they can be consumed and expelled repeatedly.

In 2018, Microplastic research began in the Bay of Fundy region in with sites selected in southwestern New Brunswick. Over the next 2 years, sediment and bivalve samples were removed from various sites throughout the Bay with the most southeastern site in Chebogue Point in Yarmouth County, Nova Scotia. Bivalves, mostly soft-shell clams and blue mussels were harvested from each site along the surrounding sediment, the main objective being a comparison of the amount of microplastic in bivalve tissue with the amount found in its surrounding environment.

Laboratory analysis confirmed microplastics were present in all collected sediment and bivalve samples. The results showed that all the bivalves contained multiple microplastics, in similar concentrations as the sediment they were removed from. Another interesting result was in the type of plastic found. Fibres were the most common plastic, followed by fragments, with films and spheres appearing less often. Another disturbing preliminary trend shows that bivalve size is a significant factor in microplastic retention suggesting that bivalves may be at greater risk during their earlier stages of development.

This research in ongoing and will continue to expand to the southern portion of the Gulf of Saint Lawrence and include the province of Prince Edward Island.

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