Arctic sea ice algae heavily contaminated with microplastics

Scientists have discovered that Melosira arctica, an alga that grows under Arctic sea ice, contains ten times more microplastic particles than the surrounding seawater. This alarming concentration at the base of the food web poses a significant threat to marine creatures that feed on the algae both at the sea surface and in the deep sea. 

Researchers from the Alfred Wegener Institute recently published these findings in the journal Environmental Science and Technology.

Melosira arctica plays a crucial role in the Arctic ecosystem. During the spring and summer months, it grows rapidly under the sea ice, forming meter-long cell chains. As the cells die and the ice melts, the algae clump together. They can then sink several thousand meters to the bottom of the deep sea within a single day. These aggregates serve as an essential food source for bottom-dwelling animals and bacteria.

However, the research team led by Dr. Melanie Bergmann found that these algae clumps also transport a dubious cargo: microplastics. 

“We have finally found a plausible explanation for why we always measure the largest amounts of microplastics in the area of the ice edge, even in deep-sea sediment,” Dr. Bergmann reports. 

What the study found about Arctic sea ice

Researchers were only aware from earlier observations that microplastics accumulate in the ice during the formation of sea ice. As the ice melts, it subsequently releases microplastics into the surrounding water.

“The speed at which the Alga descends means that it falls almost in a straight line below the edge of the ice. Marine snow, on the other hand, is slower and gets pushed sideways by currents so sinks further away. With the Melosira taking microplastics directly to the bottom, it helps explain why we measure higher microplastic numbers under the ice edge,” explained Dr. Bergmann.

The team collected samples of Melosira algae and surrounding water from ice floes during an expedition aboard the research vessel Polarstern in summer 2021. The scientists then analyzed the samples for microplastic content. Partners from the Ocean Frontier Institute (OFI), Dalhousie University, and the University of Canterbury collaborated to do this.

The surprising result revealed that the algae clumps contained an average of 31,000 ± 19,000 microplastic particles per cubic meter. This concentration is about ten times higher than the surrounding water. 

“The filamentous algae have a slimy, sticky texture, so it potentially collects microplastic from the atmospheric deposition on the sea, the sea water itself, from the surrounding ice and any other source that it passes. Once entrapped in the algal slime they travel as if in an elevator to the seafloor, or are eaten by marine animals,” explained study co-author Deonie Allen of the University of Canterbury.

An important food source polluted

As ice algae are an important food source for many deep-sea dwellers, these microplastics could potentially enter the food web. This then affects not only the deep-sea creatures but also those at the sea surface.

Previous studies involving AWI showed that microplastics were particularly widespread among ice-associated zooplankton organisms. This could explain their entry into the food chain. Fish like polar code consume Zooplankton. The cod are then eaten by seabirds and seals, and ultimately by polar bears.

A detailed analysis of the plastic composition found in the Arctic revealed various types of plastics. These include polyethylene, polyester, polypropylene, nylon, acrylic, and more. This mix of substances, combined with different chemicals and dyes, creates a complex cocktail. The impact of this cocktail on the environment and living creatures remains difficult to assess.

“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. Microplastics have already been detected in human intestines, blood, veins, lungs, placenta and breast milk and can cause inflammatory reactions, but the overall consequences have hardly been researched so far,” said Bergmann. 

“Micro and nano plastics have basically been detected in every place scientists have looked in the human body and within a plethora of other species. It is known to change behaviors, growth, fecundity and mortality rates in organisms and many plastic chemicals are known toxins to humans,” said study co-author Steve Allen.

Impact of microplastics on the Arctic sea ice

The Arctic ecosystem is already under considerable stress due to the climate crisis. The additional exposure to microplastics and the chemicals they contain could further weaken these organisms, exacerbating the threats they face. 

“So, we have a combination of planetary crises that we urgently need to address effectively. Scientific calculations have shown that the most effective way to reduce plastic pollution is to reduce the production of new plastic,” said Allen. “This should therefore definitely be prioritized in the global plastics agreement that is currently being negotiated.”

As this research sheds light on the alarming presence of microplastics in Arctic algae, it highlights the urgent need for further investigation and action to mitigate the potential consequences on the fragile Arctic ecosystem.

More about Arctic sea ice

Arctic sea ice plays a vital role in maintaining the Earth’s climate and sustaining the Arctic ecosystem. Its importance lies in various aspects, including regulating global temperature, supporting marine life, and influencing ocean circulation.

Regulating global temperature

Arctic sea ice acts as a natural reflector. It reflects sunlight back into space and preventing the Earth from absorbing excessive solar radiation. This phenomenon is known as the albedo effect. The darker ocean surface absorbs more sunlight as the sea ice melts. This leads to increased ocean temperatures and further accelerating the melting process. Ultimately, this cycle contributes to global warming.

Supporting marine life

The Arctic ecosystem relies heavily on sea ice. It provides a habitat for a wide range of organisms, including algae, plankton, fish, seals, and polar bears. The sea ice plays a critical role in the survival and reproduction of these species. It is also a vital component in the overall food chain.

Influencing ocean circulation

Arctic sea ice also affects global ocean circulation. The ocean then releases freshwater as the sea ice melts. This lowers the salinity and density of the surface waters.

This disrupts the process of thermohaline circulation, which relies on the sinking of cold, dense waters to drive the movement of warm water from the tropics toward the poles. This disruption can lead to changes in global weather patterns, impacting climate systems worldwide.

Climate change has significantly impacted Arctic sea ice, resulting in a rapid decline in its extent and thickness. The primary cause is the increase in greenhouse gas emissions, which trap heat in the Earth’s atmosphere, raising global temperatures. As a result, the Arctic region is warming at more than twice the rate of the global average, causing the ice to melt at unprecedented rates.

The loss of Arctic sea ice has several consequences:

Altered ecosystems

The disappearance of sea ice threatens the habitats and food sources for various Arctic species. This leads to population declines and disruptions to the food web.

Rising sea levels from melting Arctic sea ice

The melting of Arctic sea ice does not directly contribute to sea-level rise, as it is already floating on water. However, the loss of sea ice accelerates the melting of the Greenland ice sheet, which does contribute to rising sea levels, threatening coastal communities and ecosystems.

Extreme weather events

Changes in the Arctic can influence weather patterns across the globe. As the Arctic warms, the temperature difference between the poles and the equator decreases, disrupting the jet stream and causing extreme weather events such as heatwaves, cold snaps, and storms.

Geopolitical tensions

The receding ice opens up new shipping routes and makes natural resources, such as oil, gas, and minerals, more accessible. This can lead to increased competition and geopolitical tensions among nations with interests in the region.

In conclusion, Arctic sea ice plays a crucial role in regulating the Earth’s climate and maintaining the health of its ecosystems. Climate change is posing a significant threat to the Arctic, and the consequences of sea ice loss can have far-reaching impacts on the global climate, biodiversity, and human societies. Reducing greenhouse gas emissions and curbing global warming require urgent action to mitigate these risks.

More about microplastics

Microplastics are tiny plastic particles that measure less than 5 millimeters in size. They originate from various sources, including the breakdown of larger plastic debris, microbeads in personal care products, synthetic fibers from textiles, and microplastic pellets used in manufacturing processes. These particles are pervasive in the environment, polluting oceans, rivers, soils, and even the air we breathe.

Microplastics have several negative impacts on the environment and ecosystems:

Ingestion by wildlife

A wide range of aquatic and terrestrial organisms can mistake microplastics for food. These include plankton, fish, birds, and mammals. Ingestion of microplastics can lead to physical injury, blockages in the digestive system, reduced nutrient absorption, and even starvation, as the particles give a false sense of fullness.

Bioaccumulation and biomagnification

Organisms lower in the food chain can accumulate microplastics in their tissues when they ingest them. Predators higher up in the food web can receive them when microplastics are transferred to them. This process is known as biomagnification. Higher concentrations of microplastics can expose top predators, including humans, to them.

Transport of contaminants

Microplastics can adsorb and carry various pollutants. These include heavy metals and persistent organic pollutants (POPs). The tissues of organisms that ingest them can have heavy metals and POPs released into them. This can lead to toxic effects on the organisms, potentially impairing their growth, reproduction, and survival.

Habitat alteration

Microplastics can accumulate in sediments and soil, altering the physical properties of these environments. This can impact the living conditions of organisms, such as benthic species that dwell on the ocean floor or invertebrates living in soil, potentially affecting their distribution and abundance.

Ecosystem impacts

The presence of microplastics in the environment can also have indirect effects on ecosystems. For example, their ingestion by filter feeders, such as mussels and oysters, can reduce the efficiency of these organisms in filtering water, leading to decreased water quality and changes in nutrient cycling.

Despite growing awareness of the microplastic problem, there is still much to learn about the full extent of their impacts on the environment and ecosystems. Research is ongoing to better understand the fate of microplastics in the environment, the mechanisms by which they cause harm, and the potential long-term consequences for ecosystems and human health.

To mitigate the negative impacts of microplastics, it is crucial to reduce plastic waste, improve waste management systems, and promote the development of sustainable alternatives to plastic materials. Public awareness and policy interventions can also play a significant role in addressing the microplastic issue and protecting the environment.

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