Kennedy Bucci

Plastic pollution is a growing global concern. Large pieces of plastic have been found almost everywhere on Earth, from the most visited beaches to remote, uninhabited islands. Because wildlife are regularly exposed to plastic pollution, we often ask what effects plastics have on the animals.

Over time, macroplastics (plastic debris larger than five millimetres in size) break up into tiny particles called microplastics (smaller than five millimetres), which can persist in the environment for hundreds of years.

Macroplastics are known to cause detrimental effects for wildlife. Individual animals can ingest large pieces or become entangled in plastic items, such as fishing gear, and suffocate or starve to death. Although there is no question that macroplastics are harmful to wildlife, the effects of microplastics are not as straightforward.

While many studies find microplastics can affect the gene expression, growth, reproduction or survival of an animal, others conclude that microplastics have no negative effects. The lack of clear consensus makes it more difficult for decision-makers to enact effective policies to mitigate plastic pollution.

Not all plastics are the same

We recently took a deep dive into the research that has looked at how plastic pollution affects aquatic and terrestrial wildlife.

We found that while macroplastics continue to cause detrimental effects to individual animals, they are also causing larger-scale changes to populations of animals, communities and ecosystems. For example, plastic pollution can introduce invasive species to new habitats by transporting organisms hundreds of kilometres from their native range, changing the composition of species in a community.

The effects of microplastics, however, are much more complicated. Of the studies we included in our review, nearly half (45 per cent) found that microplastics caused an effect. Some studies saw that microplastics caused animals to have shorter lives, eat less or swim slower, and others saw changes in the number of offspring produced, and changes in the genes being expressed. Yet, 55 per cent of the studies didn’t detect any effects.

Why do some studies detect effects while others do not? There are several possibilities. For one, the researchers used different experimental designs in their lab experiments.

There’s also the issue of using the term microplastics, which refers to a complex mixture of plastics that vary in material (such as polyethylene, polystyrene or polyvinyl chloride), the chemicals associated with them (including additives, fillers and dyes), as well as their size and shape. Each of these characteristics, along with how much plastic the animal is exposed to in the experiment, could affect their potential to detect an effect.

Microfibres and microbeads

For example, we saw that when studies exposed crustaceans to polystyrene, a type of plastic used to make disposable containers, lids and cutlery, the crustaceans generally produced more offspring. But when they were exposed to polyethylene or polyethylene terephthalate, which is used to make plastic bags and beverage bottles, the crustaceans produced fewer offspring.

We also found that studies using smaller particles are more likely to detect an effect. This may be because smaller particles are more easily consumed by small organisms, or because they can move across the cell membrane and cause harmful effects such as inflammation.

Microbeads are found in exfoliating products such as face cleansers and toothpaste. Several countries have banned their production and sale (photo by Shutterstock)

When it came to the shape of the plastic, microfibres (from clothing or rope) and fragments were more likely to have a negative effect on the organism compared to spheres (from facial cleansing products). For example, one study found that microfibres were more toxic to a species of marine shrimp than microplastic fragments or spheres.

Finally, one might expect animals to be more harmed when they are exposed to higher concentrations of microplastics. While it’s true that crustaceans were more likely to die when exposed to increasing doses of microplastics, the effect on reproduction was more complex. The number of offspring increased with extremely high doses, but decreased at lower doses, similar to what is seen in the environment.

Many types, many outcomes

Based on our review, we believe future research needs to recognize the complexity of microplastics and scientists need to design their tests strategically so that we can really understand how the different types, sizes, shapes, doses and the duration of exposure to microplastics affect wildlife.

Several countries, including Canada, the United Kingdom and United States have recently banned plastic microbeads – the spherical beads and fragments in face wash, body scrubs and toothpaste – because they were contaminating the environment and could cause negative effects in aquatic animals. Although this legislation reduces one type of microplastic in the environment, it is irrelevant to countless others.

Only if we have a better understanding of how the different types, shapes and concentrations of microplastics affect wildlife can we make better policy decisions. If, for example, microfibres are indeed found to be more harmful than spheres, we could focus our attention on keeping these fibres from entering our waterways from known sources, such as from washing machines.

Chelsea Rochman is an assistant professor of ecology and evolutionary biology at the University of Toronto. Kennedy Bucci is a PhD student in the department of ecology and evolutionary biology at the University of Toronto.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Beyond our oceans: Microplastics pollute rivers and lakes too

ullahnor — Fri, 27 Apr 2018 15:20:47 +0000

Beyond our oceans: Microplastics pollute rivers and lakes too

ullahnor Fri, 04/27/2018 - 11:20

Cutline

Researchers are finding plastics in fish in freshwater ecosystems (Shutterstock)

Chelsea Rochman

Kennedy Bucci

Topic

Our Community

Department of Ecology & Evolutionary Biology

Environment

Faculty of Arts & Science

The Conversation

Subheadline

The Conversation with Kennedy Bucci and Chelsea Rochman

When you think of microplastic pollution, plastic debris less than five millimetres in size, you likely envision the ocean – probably because ocean gyres gained notoriety for being a microplastic soup.

But what about our lakes, rivers, forests and fields? They can be just as contaminated with microplastic debris as the oceans.

Until recently, these environments were described as conduits – ways for plastics to get to the oceans. But now we’re seeing rivers, lakes and soil in a different light, as reservoirs for plastic particles.

We now know that agricultural land, surface waters, freshwater lakes and river sediments are also contaminated.

In the past five years, researchers have started to study the sources, fates and effects of microplastics in freshwater and terrestrial ecosystems, but only a handful of studies have been done so far.

Microplastics in our Great Lakes

Here in North America, when we think of freshwater, we often think of the Laurentian Great Lakes. They hold more than one fifth of the world’s freshwater, are the basis of billions of dollars in economic activity and are a point of pride for those living on their shorelines.

For the Indigenous peoples of Canada, the Great Lakes hold even more importance. There are more than 75 First Nations communities in the Great Lakes watershed, all of whom fish the waters for food or sport.

It is no secret, however, that the Great Lakes have had their share of ecological problems. Most have been caused by us, including the ongoing issues of nutrient-loading, invasive species like zebra and quagga mussels, tributary dams and reduced ice cover.

Recent research now shows the Great Lakes also contain microplastic pollution, with the highest concentrations in heavily urbanized areas, like Toronto and Detroit.

Plastic debris washed up on the shore of Lake Ontario, near Toronto (photo courtesy of Kennedy Bucci)

Another study found that a litre of sediment from the St. Lawrence River contained up to 1,000 spherical microplastics – on par with the world’s most polluted marine sediments.

Microplastics are now globally distributed in freshwater lakes and rivers. They’ve been found in North America, Europe and Asia.

Contaminated habitats, contaminated wildlife

Microplastics fill the digestive tracts of the wildlife that inhabit freshwater ecosystems.

In a Texas river basin, for example, 45 per cent of captured sunfish had reportedly consumed microplastics. Another study found that 12 per cent of gudgeons, a small bottom-dwelling fish, caught in a French stream had microplastics in their guts.

Closer to home, our lab has found that fish from the Great Lakes can have up to 40 microplastics in their digestive tracts. Many of these are microfibres – small strands of synthetic textiles, some of which come from our clothing.

In marine animals, microplastics can alter gene expression, cause inflammation in tissues and affect reproductive success. But we know much less about the effects in freshwater wildlife, which may be different than in marine animals. For example, marine fish drink water, whereas freshwater fish absorb water through their gills and skin; this may lead to different exposure concentrations of microplastics.

Although some studies have examined population- and community-level effects, most have focused on the effects on individual animals. As a result, evidence regarding the effects of microplastics on populations of animals are scarce. We need to ask how these pollutants affect survival, reproduction and the interactions between species in a community.

Our lab is beginning to do just that. For example, an ongoing study is comparing the effects of a range of microplastics found in Lake Ontario, and measuring their effects on freshwater fish survival, development and reproduction.

Calling all scientists

The oceans cover more than 70 per cent of our globe. Still, the biodiversity on land and in freshwater is more than five times that in the oceans. In addition, the global population relies on freshwater and terrestrial ecosystems for food, water and recreation. As such, microplastic research must include all ecosystems.

We are using plastic products at an unprecedented rate, and have already generated an estimated 6,300 metric tonnes of plastic waste. Although some of this is recycled, about 79 per cent is accumulating in landfills or the environment.

Moving forward, we must invest in gathering more scientific evidence about the sources, fate and effects of microplastics in terrestrial and freshwater ecosystems. At the same time, we know enough about plastic pollution to act.

As Canada takes presidency of the G7 this year, we applaud our government, which has committed to take leadership in preventing further contamination of the planet by plastic pollution.

Kennedy Bucci is a graduate student at the University of Toronto, and Chelsea Rochman is an assistant professor of ecology and evolutionary biology at the University of Toronto

This article was originally published on The Conversation. Read the original article.