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Beluga whales may be consuming hundreds of thousands of microplastics each year due to the fish they eat.
Canadian researchers found that even in the remote waters of the Arctic, the whales aren't safe from human impacts. This exposes them to a range of potential health impacts.
Whales living in the Arctic may be ingesting up to 145,000 small pieces of plastic each year through their prey.
Canadian researchers found that around a fifth of fish eaten by beluga whales are likely to contain microplastics. These plastics, the remains of larger items that have broken down over time, can cause a range of effects on animal life, but their overall impact on the whales remains uncertain.
Rhiannon Moore, the study's lead author, says, 'We use so much plastic in our society, and when improperly discarded they break apart into smaller and smaller pieces, and that makes them easy to be transported in ocean environments.
'The results of these studies just further point to the reality that microplastics don't stay in one place. They move through the air, the water, they're in sediment and now we understand they're moving through the food chain.'
Alex McGoran, a PhD student at the Museum who is looking at how microplastics move through marine environments, says that while the figure is high, many microplastics may pass rapidly through the system.
'The headline figure of 145,000 pieces of microplastic doesn't mean that all of it is maintained in the body,' she says. 'It may pass through and only be in the body for a short time which suggests the impact could be less on the whales.
'Another study on marine mammals found that while every studied individual had plastic in them, it was not at high levels. This highlights the need for more research into microplastics and their health effects.'
The study, led by researchers at Simon Fraser University, was published in Science of The Total Environment.
Microplastics are any type of plastic that is smaller than 5 millimetres in size. While over five trillion plastic pieces are estimated to be floating in the sea, it is an issue that has only been appreciated recently.
'Microplastics have been around for a long time,' Alex says. 'The first reports were in the 1970s but were mostly notes about the fact they had been observed in papers focusing on other topics.
'It wasn't until the 2000s that scientific research began to escalate and the term was coined. It took scientists a while to realise this material was abundant and potentially a threat, and it is now publicly known.'
The diverse range of materials covered by microplastics mean that its impacts are equally diverse and difficult to generalise.
'There isn't just one problem with plastic,' Alex says, 'and it's hard to say what impacts microplastics have on an organism. Unlike certain chemicals such as pesticides, plastic is a soup of pollutants.
'Microplastics can contain dyes and plasticisers that can leach into animals and cause cancers, affect hormonal cycles through oestrogen-mimicking chemicals, and can scratch or block the digestive tract.
'The effects of these different plastics then varies by animal, but one particular group that are affected are the crustaceans. Microplastics in their stomach can form into balls that can become too large to enter the intestines.'
Scientists are concerned that microplastics in prey animals could build up in their predators in a process known as bioaccumulation. While only small amounts are found in each prey animal, predators can end up with significant amounts in their body as they eat multiple animals.
This process can have devastating impacts on predators, with bird of prey populations suffering from brittle eggs in the twentieth century after the pesticide DDT accumulated in this way.
In this study, the researchers wanted to investigate whether beluga whales living in remote Arctic waters are affected in a similar way by plastic pollution.
The researchers sampled five fish species that beluga whales are known to eat, including Arctic cod, capelin and four-horn sculpin. They found that 21% of the fish had microplastics in them, with an average of 1.5 fragments per fish.
The microplastics were predominantly in the form of fibres, which originate from textiles, clothing and synthetic ropes.
Based on the number of fish beluga whales need to survive, the scientists found that an individual whale may eat between 3,800 and 145,000 microplastic fragments each year. While the figures are large, the study is based on a relatively small sample size of seven whales, and 117 fish, which may not provide a representative result for populations at large.
The health impacts of microplastics are also uncertain. While there are some studies suggesting that microplastics can help carry toxic chemicals into marine predators, it can be difficult to differentiate the impacts of these fragments from pollution leaching directly from the sea itself.
'Many studies are limited in this way, as they can't distinguish seaborne pollutants from those from plastics,' Alex says. 'There's also a need to look at environmentally relevant concentrations.
'Early studies used levels of plastics at up to 20 times more than is found in the environment, which is a worst-case scenario and not necessarily what happens in reality.'
Research into microplastics is a rapidly evolving field, with researchers now looking into even smaller particles known as nanoplastics. These are microscopic fragments that may be able to pass between cells and even enter the brain.
Finding out more about the diverse forms of microplastic, and the impacts they can have, will help scientists better inform governments about how to best protect nature from these tiny remnants of humanity's creations.