Microplastics can affect the formation and melting of Arctic sea ice

Plastic pollution in the oceans has become an important societal problem, as plastics are the most common and persistent pollutants in the oceans and beaches of the world. In the common imaginary, plastic wastes are often associated with drifting bottles in the ocean, fishing gear washed up on beaches or plastic bags in which turtles think they are jellyfish and eat.

But these larger particles are just the tip of the iceberg. Small particles are also an important part of the problem. Plastic particles smaller than five millimeters are called microplastics. They can come from deliberate motives (such as cleaning agents or personal care products), the breakdown of large pieces of plastic or microfibers of textiles.

The impact of microplastics on the environment and human health is still under study.

Arctic impact

If people assume that the Arctic environment is not affected by what humans are throwing back into the oceans, they are wrong. The crystal clear waters of the Arctic Ocean are under the silent threat of those particles that drift long distances with ocean currents.

Concentrations of microplastics in the Arctic are expected to increase rapidly due to the increasing supply of freshwater and the intensification of maritime traffic and resource development activities. Given the unique vulnerability of Arctic marine ecosystems, it is urgent to assess the distribution, pathways and fate of microplastics in the Arctic.

In a recently published article in Marine Pollution Bulletin, we investigated whether and how microplastics could be integrated into the structure of sea ice. Microplastics in sea ice could affect the absorption of solar radiation incident. This affects the albedo of sea ice – the way the ice reflects solar energy – one of the key properties of sea ice in terms of regulating heat exchanges between the sea ice and the sea ice. ocean and the atmosphere.

Measure the albedo

Changes in sea ice albedo would have a strong impact on the annual growth and sea-ice melting cycle. To test our hypothesis, we have initiated a study of the microcosm of the sea ice. [Sea-ice Environmental Research Facility at the University of Manitoba]an outdoor pool where you can grow sea ice.

Two sets of 12 microcosms, measuring one cubic meter, were made using galvanized aluminum tubes as reinforcements and cotton sheets as walls. The first set was used to measure the light levels, while the second set was used to collect sea ice samples. We manually added microplastic particles to monitor their incorporation into the sea ice as they progressed. measure of its growth. Four different concentrations were used: control (no added particles), low, medium, and high (approximately 120, 380, and 1200 particles per liter, respectively).

We used a dye called Nile Red to follow microplastics when the ice froze. Under fluorescent light, the dye shone microplastics, which allowed us to see how sea ice concentrated microplastics in its structure and, once incorporated, how these particles remained in the ice matrix.

We found high concentrations of particles on the surface of the sea ice, due to the buoyancy of the particles and the rapid formation of ice crystals, which trapped them when the ice melted in a firm layer of ice. Although microplastics had no effect on growth rates of sea ice, marked changes in sea ice albedo were observed in response to medium and high concentrations of microcosms of microplastics.

To determine the real impact of our observations on the real world, we also measured microplastic concentrations in various sea ice samples taken from the Gulf of Bothnia (Baltic Sea). We observed microplastic concentrations similar to those observed in the Arctic Ocean (8 to 41 particles per liter), but significantly lower than the concentration observed in our microcosm experiment. At these concentrations, we do not expect microplastic incorporation to have an impact on sea ice albedo.

In areas where microplastic concentrations are higher, or if the microplastic concentration is to increase, we expect the properties of sea ice to change. These changes would mainly affect albedo, but also the photochemical and photobiological processes present in sea ice, such as the availability of light for algae living at the bottom of the ice cover, with potential impacts on the base. of the Arctic food web.

---

---

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