How Embedded in the Food Chain are Microplastics?

When you think of microplastics, you likely don't think of the Arctic. But their prevalence in Arctic sea algae provides some food for thought.


As if there were not enough existential-dread-causing threats to the planet and humanity, a new one has emerged in recent years: microplastics. Due to their durability, these tiny fragments of plastic are being found everywhere from snow to our food to even our blood!

The health risks of these minuscule pollutants are not yet fully known, but a great deal of research is focused on understanding their effects. Yet how do these microplastics travel and accumulate within food chains and ecosystems? A new study from a team of researchers, including one from Dalhousie University, sheds some light on the movement of microplastics in an unexpected place — the Arctic.

Melosira arctica 

To highlight the importance of their work, the researchers point to a concerning statistic — plastic pollution levels could double in the next two decades. Alarmingly, microplastics are already being discovered in environments such as the Arctic, and within Arctic organisms including polar cod and zooplankton.

However, the focus of their study was on Melosira arctica, a species of Arctic sea ice algae that serves as a crucial source of energy for Arctic zooplankton. In fact, M. arctica accounted for nearly half of primary energy production in the Arctic in 2012.

While the algae is usually found attached to sea ice, it detaches as the ice melts and either forms masses that float in the water or sinks to the floor of the ocean, where it provides a food source for bottom-dwelling organisms.

Microplastic accumulation

Given that M. arctica is often attached to Arctic sea ice, which also contains large amounts of microplastics, the researchers hypothesized that the algae captures microplastics that are released by the melting ice.

Algae samples were collected in the Fram Strait — adjacent to Greenland — during a 2021 Arctic circle expedition of the icebreaker RV Polarstern. Following microscopic confirmation that the algae was indeed M. arctica, the research team measured the concentrations of microplastics within the samples.

Unsurprisingly, researchers discovered microplastic particles in all of the samples — nearly 400 particles in 12 samples! Interestingly, the concentration of microplastics in the sea algae samples was nearly ten times higher than in the sea water samples, supporting the team’s hypothesis that M. arctica traps microplastics from surrounding ice and sea water.

This finding raises concerns regarding the dangers of microplastic accumulation further down the food chain. As the plastic-heavy algae clumps and sinks to the ocean floor, it is consumed by bottom-dwelling organisms that are in turn consumed by fish, birds, and polar bears.

As one member of the team pointed out in a press release, “people in the Arctic are particularly dependent on the marine food web for their protein supply, for example through hunting or fishing. This means that they are also exposed to the microplastics and chemicals contained in it.”

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Borna Atrchian is an MA student in the Department of Political Science at the University of Toronto. Having previously completed a Behavioural Neuroscience degree, he is passionate about issues where politics and power intersect with psychology and human behaviour. He is interested in understanding the conditions that create distrust of the scientific community, as well as finding the most effective ways to rebuild this trust.