| Photo: Krista digging for clams
NB Naturalist Feature: Microplastics in the Bay of Fundy
By: Krista Beardy
It was a cold day in January when I first stood on the rocky shoreline of Berry Point, slightly north of the Caughey-Taylor Nature Preserve, spade in one heavily-mittened hand and a bucket in the other. At this point, I had only read about clam digging; how to spot their syphon holes, how to properly extract them without damage, and how to store them for the study in which they would become the primary focus. I was in search of Mya arenaria, more commonly called soft-shelled clams. Even though I, like many Atlantic Canadians, enjoy a delicious seaside clam bake, these bivalves had a different purpose that was far less palatable, and more than a little smelly. These clams were the species I chose as study subjects for a small project focussing on microplastic contamination in the south western region of the Bay of Fundy.
My interest in microplastics began as a result of a previous vocation. For over a decade, I had worked summers as a sea kayak guide on the eastern shore of Nova Scotia. Despite being removed from larger population centers where excessive waste may be expected, it became clear that immense amounts of debris could be found anywhere along the shoreline, even in the most rural parts of the province. To make the best of this trashy situation, I (and other like-minded guides) used encounters with marine debris as a talking point to educate our clients on this steadily growing global issue. Garbage would be fished out of the water, its destructive potential would be discussed, and the offending item would be stowed in (or on) the kayak for proper disposal upon our return to shore. We stowed everything from tangles of ropes, Styrofoam blocks, plastic bottles, plastic bags, balloons, and an endless amount of random bits and pieces of all sizes, shapes, and composition. Without exception, every load of debris that was returned to shore was primarily comprised of some variety of plastic.
To understand the problem with plastic pollution, we must first understand the properties of plastic. Plastic is a common term for a broad family of organic materials most of which are derived from petroleum products and transformed through various processes to give plastic the properties that make it so desirable. This includes such attributes as resistance to shattering, corrosion, and UV radiation as well as relatively low production cost, while offering lightweight, airtight, and waterproof solutions to consumer needs. These properties that make plastic so incredibly versatile and durable are also what makes it so problematic once it enters the marine environment. To add even more gravity to the issue, the amount of time it takes for plastic to completely degrade is extremely long and poorly understood. What we do know is that as plastic remains in the marine environment, over time it breaks up into 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. This is an important factor. Consider plastic that sinks into deep waters. 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.
Where Does It All Come From?
The majority of plastic pollution can be attributed to land-based activities. Trash from poorly managed or overflowing sources like landfills and temporary garbage receptacles, and from littering. As anyone who has lived near a flowing body of water knows, this garbage is rinsed by rainfall or blown by the wind and becomes trapped in ditches and is flushed in the local river systems which eventually enters the ocean environment. The Saint John River is a good local example. Think of the amount of pollutants, plastic and otherwise, that are flushed out to sea after recent melts and flooding events.
A bigger example would be the St. Lawrence River system which connects the Great Lakes with the Atlantic Ocean. This river runs from Ontario through the province of Quebec with the banks of this river highly populated in many regions. The wastewater treatment systems servicing these regions are not designed to retain smaller plastics. Therefore, the remnants of personal hygiene products are a common sight along the shoreline. This wastewater is also a source of microplastics in the form of synthetic fibres from laundry effluent. Consider the lint trap on a clothes dryer. That is what is left over once the clothes are washed and rinsed and the grey water containing the majority of the loose fibres is flushed away.
The St. Lawrence River is also home to the St. Lawrence Seaway, a heavily traveled commercial shipping route. It is estimated that 20% of marine plastics can be attributed to at-sea industrial activities such as shipping, fishing, and aquaculture. The Bay of Fundy is home to all three of these source industries.
The Bay of Fundy
The Bay of Fundy lies between the provinces of Nova Scotia and New Brunswick and touches the U.S. state of Maine. It is known for extremely high, semidiurnal tides that can reach up to 16 metres. The Bay is funnel shaped creating extremely powerful tides with an amount of about 100 billion tonnes of water flowing in and out of the bay in a single tidal cycle. This extreme tidal activity coupled with sun exposure on extensive tidal flats suggests that the rate of plastic degradation may be intensified in this region lending greater significance to the build-up of both marine and coastline debris.
In short, there is a large amount of source material that is exposed to environmental conditions conducive for microplastic production. The importance of these coastal sediments cannot be overstated. They are critical habitat 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.
What Lies Beneath
The health of the benthic sediments also depends on a healthy and diverse population of ecosystem service providers. This relationship can provide a positive feedback loop; healthy sediment = healthy populations = healthy sediments. The Lugworm (Arenicola marina), for example, is an important ecosystem service provider that is commonly found burrowing in sandy beaches and mudflats. They eat sediment, digesting any micro-organisms and nutrients along the way. They pass the sediment as waste through their tail, leaving behind a distinct trail called a cast. The worm can make up about 30% of the biomass of an average sandy beach, making it an important source of food for wading birds and fish. Beyond serving as a food source for other creatures, these polychaetes provide another important ecosystem service called bioturbation which is the turning over of large amounts of sediment, replenishing the organic matter while providing oxygen to the upper layers of the benthos. This ensures a healthy habitat for other animals and microorganisms. However, in sediments containing microplastics, Lugworm activity is reduced, and the worms produce fewer casts which, in turn, reduces the primary productivity of these habitats. Ingestion of microplastics by other species who, like the Lugworm, are closer to the base of the food web, is a cause for concern since little is known about the consequences. Many other organisms that have similar feeding behaviour, such as starfish, sea cucumbers, lobsters, and crabs may be similarly affected. This is a problem since 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.
Back to Berry Point
My first day of clam digging in Berry Point was very successful. Afterwards, with my newfound expertise, I continued sampling different areas, digging up clams between the town of St. Stephen and the Saint John Harbour, and then extended my work to the island of Grand Manan. Sediment samples were also taken from beside each harvested bivalve. My main objective was to compare the amount of microplastic in clam tissue with the amount found in its surrounding environment. Once back at the lab, the clams were digested to remove all tissue. The same digestion was performed to remove excess organic matter from the sediment. Once the process was complete, the resulting solutions were passed through a filter to trap the microplastics. What was left looked something like this…
Microplastics were found in all sediment samples and in all bivalve samples, except one – a control sample taken from a marine protected area. Those were the results from a study performed in winter due to the timing of the funding initiative, but it turns out that the bivalves are more actively feeding in the warmer waters and longer days of summer, which is when I performed my latest round of sampling. This round also included the entire coastline of the Bay of Fundy (New Brunswick including Grand Manan Island, and Nova Scotia).
The results showed that all of the bivalves contained multiple microplastics, in similar amounts as the sediment they were removed from. It is quickly becoming safe to say that if it lives and feeds in sediment with microplastics, then chances are it is consuming microplastics. Another interesting result was in the type of plastic found in both the sediment and clam samples. Fibres were the most common plastic, followed by fragments, with films and spheres appearing less often. Under a microscope, many of these fibres look like miniature versions of commonly used industrial rope possessing distinctive dye patterns. Much of this could be attributed to the large amounts of lost or discarded rope, a ubiquitous sight on the Bay of Fundy shoreline. However, further analysis is required to confirm this. Another disturbing trend shows that bivalve size is a significant factor in microplastic retention suggesting that soft shelled clams may be at greater risk during their earlier stages of development.
What Can We Do?
Once plastic waste enters any body of water, recovery becomes impractical, if not impossible in some cases. The most practical solutions call for the identification of regional sources of debris and the development of upstream interventions. A good example of this upstream intervention is in the case of microbeads in personal hygiene products. In this case, scientists presented observations of microplastic pollution and their potential for ecosystem destruction. This was followed by a public movement to pressure policymakers to make changes to the industry.
While waiting for the implementation of large-scale interventions, there are things we can do on a small scale that will add up to less. We can start by reducing the usage of anything with unnecessary plastics. Find and support businesses that show responsible practices by using less waste. Find alternatives to single-use plastics. From personal hygiene products to convenience food, natural or reusable alternatives are often available. Also, do not shy away from cleaning someone else’s mess. This is an act that also creates an impact on those who see it and practices like this catch on fast. And finally, join in and support community clean up initiatives. These small habits may seem insignificant considering the size of the overall problem, but change must start somewhere. It might as well start here.
What Can YOU Do To Help?
- Fill your own reusable bottles with water.
- Avoid disposable products i.e. utensils, razors, lighters, batteries.
- Bring your own reusable bags.
- Skip the straw.
- Say ‘NO’ to Styrofoam.
- Bring your own cup or thermos when buying drinks.
- Cigarettes are litter too. Use a heat proof container and safely dispose in trash.
- When you can, buy products in glass or metal containers.
- Look for items with the least amount of packaging.
- Avoid individually wrapped items (cheese slices, juice boxes, etc.)
- Purchase items in containers that can be reused.
- Buying in bulk can reduce packaging.
- Urge your grocery store to carry products in bulk or use less packaging.
- Complete the loop by buying products made with recycled materials.
- Spread the word!
- JOIN A SHORELINE CLEAN UP NEAR YOU!