Ocean Microplastics Show Up in Arctic Ice Algae
Last summer, we travelled to the remote Arctic Hausgarten observatory area in the eastern Fram Strait (west of Svalbard, Norway) on a research ship. The samples we collected there included ice cores, sea water and ice algae from large packs of floating ice called ice floes. These form 1–2 meter thick “plates” of sea ice across the Arctic Ocean, some of which melt over the summer period.
Algae grow on the underside of these ice floes. Melosira arctica – nicknamed “snot” due to its sticky, slimy and green nature – is one of the major algae species in the Arctic Ocean. It is an essential organism both in the Arctic food web and for marine life overall.
These ice algae provide nutrition for plankton and various other marine organisms in the Arctic. The algae also act as a conveyor belt of food for the organisms that live on the sea floor. As the ice melts, the algae detach and sink to the bottom where they are eaten by animals such as sea cucumbers and brittlestars.
Ice algae are also a carbon sink, using CO2 from the atmosphere and light energy from the sun to produce organic matter through photosynthesis – a process known in ecology as “primary production”. In 2012, these algae accounted for 45% of the Arctic’s primary production.
But now we’ve found that Arctic ice algae contain microplastics. This in itself may not be surprising: plastic has been found in every environment so far investigated on Earth. But the quantities we found were startling.
We discovered an average of 31,000 microplastic particles per cubic meter of Melosira arctica – a magnitude ten times higher than recorded in the surrounding water. Most of these particles were very small (less than 10 micrometers) and included many different types of plastic. The contamination of the ice algae could have major consequences for ecosystems and the climate.
An elevator to the seabed
These particles may come from the surrounding sea water, the supporting sea ice (either trapped when the sea ice forms, or from the movement of liquid and particles through the ice as it melts), or from atmospheric microplastics that have been deposited on the ice and sea surface. While the process by which sea ice algae take in these microplastics is not yet well understood, it is clear they are highly effective at “collecting” these small plastic particles.
In our earlier research, we were puzzled that the largest amount of microplastic on the Arctic seabed was always found underneath the sea ice melting zone along the ice edge, even in deep-sea sediment. The movement of Melosira clumps from the sea and ice surface to the seabed helps to explain why.
The speed at which the algal clumps descend means they fall rapidly almost in a straight line below the edge of the ice. Other algae, which become “marine snow” (a term used for organic material that slowly drifts to the seafloor), fall much slower. These are often eaten as they descend and are also pushed sideways by currents, so sink to the seabed much further away from the ice edge.
How microplastics could become trapped in Arctic sea ice algae and sink to the seabed. Bergmann et al. (2023), CC BY-NC-ND
Why is it a problem?
Melosira feeds essential Arctic seafloor and marine ecosystems. Its position at the bottom of the food chain means there is a risk of microplastics being passed upwards through the marine food web.
This threat is particularly acute in the area we studied, as the Melosira sampled had collected even very small microplastics. Smaller microplastic particles are more likely to be transferred across cell membranes.
Research finds that microplastics and their associated chemicals can alter the growth, function and breeding of marine species such as plankton and fish. It is extremely difficult to perform experiments on Arctic or deep-sea species because of the challenges associated with replicating their environmental conditions. However, one laboratory study found that microplastic exposure caused egg production rates to increase by up to eight times in Arctic zooplankton – a response that is probably the result of stress.
The impact of microplastic contamination on Melosira itself is not yet known. But it’s possible that microplastics change Melosira’s abundance, lifespan and health.
Microplastics that are stuck to the outside of algae could lower photosynthetic rates by blocking out sunlight. And if particles enter the algal cells, then they could damage the parts of the cell where photosynthesis takes place (called chloroplasts) and therefore also impede this process. This could affect the export of carbon by Melosira from the air or sea to the seabed, and thus alter the processes underlying this important Arctic carbon sink.
Arctic ice algae are collecting high quantities of microplastics – a previously unknown hotspot. But our findings are likely just the “tip of the iceberg”. They should accelerate conversations about the importance, and potential impact, of microplastics in Arctic sea ice algae on the ecosystems that these vital algae support.
Deonie Allen is a Research Fellow at University of Birmingham.
Melanie Bergmann is a Senior Scientist at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research.
Steve Allen is Ocean Frontier Institute researcher at Dalhousie University.
This article appears courtesy of The Conversation and may be found in its original form here.
The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.
How old is that microplastic? A new way to estimate the age of microplastics in the upper ocean
Researchers develop a method to estimate the age of microplastics in the ocean, and find that offshore microplastics can range from 1 to 3 years old while nearshore microplastics can range from 0 to 5 years old
Peer-Reviewed PublicationIMAGE: MICROPLASTIC SAMPLES COLLECTED FROM THE OCEANS. PLASTIC FRAGMENTS LESS THAN 5 MM IN LENGTH ARE CATEGORIZED AS MICROPLASTICS. THE SCALE BAR SHOWS A LENGTH OF 2000 ΜM OR 2 MM. view more
CREDIT: KYUSHU UNIVERSITY/ASAHI KASEI CORPORATION
Fukuoka, Japan—Researchers from Kyushu University and Asahi Kasei Corporation have developed a new way to estimate the age of microplastics found in the upper oceans. The method involves a combination of analyzing plastic oxidation levels with environmental factors such as UV exposure and ambient temperature.
The team applied their new method to estimate the age of microplastics found in nearshore and offshore sites in the North Pacific Ocean. They found that the age of microplastics in nearshore regions ranged from 0 to 5 years old, whereas microplastics from offshore regions ranged from 1 to 3 years old. Their findings were published in the journal, Marine Pollution Bulletin.
In marine environments from lakes to oceans, plastics are the most abundant type of pollutant. As plastic waste is exposed to the elements they eventually break down and fragment. Plastic waste that has broken down to less than 5 mm in length are called 'microplastics.'
"Microplastic pollution is recognized as a global problem. In a previous study, we found that there are about 24 trillion grains of microplastics floating on the surface layer of the ocean," explains Professor Atsuhiko Isobe of Kyushu University's Research Institute for Applied Mechanics, who led the study. "However, there is still little we know about its effects on the environment or to living creatures. Another big question we have is how long microplastics drift through the ocean."
To find out how old microplastics found in the ocean can be, Isobe and his team began by investigating what metrics could be used to measure microplastic age in the first place.
"The most common material in plastic is called polyethylene. We know that as polyethylene interacts with the environment it, oxidizes and degrades," explains Rie Okubo, a researcher at Asahi Kasei Corporation and first author of the study. "This degradation level can be measured using the change in the material's molecular weight and something called the carbonyl index. Simply, when polyethylene degrades its carbonyl index increases and molecular weight decreases."
Of course, that's not enough. Since microplastics are being exposed to the elements the team also needed to standardize how temperature and UV radiation affects plastic degradation. The team first conducted a series of exposure experiments to polyethylene material and collected data on how various combinations of UV and temperature affected the material's molecular weight and carbonyl index.
The team found that UVER—ultraviolet erythemal radiation, a measurement of UV radiation at ground level—and seawater temperature were the two biggest contributors of plastic degradation.
"Once we had this data, we began to apply it to our microplastic samples. All our samples came from the upper ocean, up to one meter from the water surface," continues Okubo. "We also collected microplastics from a range of areas. Some samples were collected nearshore to Japan, ranging from 10 to 80 km off the coast. Other samples were collected offshore, in the middle of the North Pacific Ocean and Philippine Sea."
By analyzing the collected microplastics, the team was able to estimate the age of each induvial sample. They found that nearshore microplastics ranged from 0 to 5 years old, whereas offshore samples ranged from 1 to 3 years old.
"We hypothesize the reason why nearshore microplastics range from 0 to 5 years is because they are being frequently washed ashore and 'surviving' for a longer time. Offshore microplastics on the other hand take longer to reach that part of the ocean, hence why we didn't find microplastics over 3 years old," Okubo explains. "These offshore microplastics are also likely removed from the upper oceans by settling deeper into the waters."
The researchers hope that the new method will give them better insights into how microplastics are generated and spread in the environment. The data will also help in developing more accurate simulations to track microplastics across the ocean.
Isobe concludes, "Our research and understanding of microplastics is still very new, and thanks to this data we've gained a little more understanding on the fundamental science of microplastics. Our next step will be to investigate how mechanical stimuli like ocean waves and currents can degrade plastics, so we can collect even more accurate data.
Dr Okubo looking through a microscope studying microplastic samples. Plastic fragments less than 5 mm in length are categorized as microplastics.
Prof Atsuhiko Isobe and crew collecting microplastic samples from the upper oceans. The upper ocean is measured down to one meter from the water surface.
Prof Atsuhiko Isobe and gathering the microplastic samples collected from the upper ocean.
CREDIT
Kyushu University/Isobe Lab
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For more information about this research, see "Estimation of the age of polyethylene microplastics collected from oceans: Application to the western North Pacific Ocean," Rie Okubo, Aguru Yamamoto, Akihiro Kurima, Terumi Sakabe, Youichiroh Ide, Atsuhiko Isobe Marine Pollution Bulletin, https://doi.org/10.1016/j.marpolbul.2023.114951
About Kyushu University
Kyushu University is one of Japan's leading research-oriented institutes of higher education since its founding in 1911. Home to around 19,000 students and 8,000 faculty and staff, Kyushu U's world-class research centers cover a wide range of study areas and research fields, from the humanities and arts to engineering and medical sciences. Its multiple campuses—including one of the largest in Japan—are located around Fukuoka City, a coastal metropolis on the southwestern Japanese island of Kyushu that is frequently ranked among the world's most livable cities and historically known as Japan's gateway to Asia. Through its Vision 2030, Kyushu U will 'Drive Social Change with Integrative Knowledge.' Its synergistic application of knowledge will encompass all of academia and solve issues in society while innovating new systems for a better future.
About Asahi Kasei
The Asahi Kasei Group contributes to life and living for people around the world. Since its foundation in 1922 with ammonia and cellulose fiber business, Asahi Kasei has consistently grown through the proactive transformation of its business portfolio to meet the evolving needs of every age. With more than 46,000 employees worldwide, the company contributes to sustainable society by providing solutions to the world’s challenges through its three business sectors of Material, Homes, and Health Care. For more information, visit www.asahi-kasei.com.
Asahi Kasei is also dedicated to sustainability initiatives and is contributing to reaching a carbon neutral society by 2050.
To learn more, visit https://www.asahi-kasei.com/sustainability/
JOURNAL
Marine Pollution Bulletin
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Estimation of the age of polyethylene microplastics collected from oceans: Application to the western North Pacific Ocean
ARTICLE PUBLICATION DATE
14-May-2023
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