Microplastics, also known as MPs, are tiny pieces of plastic that measure less than 5 millimeters (0.20 inches) across and are known to be harmful to both the ocean and marine life. A 2022 finding estimated that there are about 51 trillion pieces of microplastics in the ocean with a combined weight of 269,000 tons, equivalent to 1,345 blue whales. But, how long have these microplastics been in the ocean and can they be tracked to determine the long-term ramifications of their ocean presence?
These questions are what a recent study published in Marine Pollution Bulletin hope to figure out as a team of researchers examined the potential age range of microplastics that reside in the upper ocean, which could help environmentalists determine both the origin and long-term impacts of microplastic fragments within the Earth’s upper ocean, which is measured down to one meter (3.28 feet) beneath the ocean's surface.
"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," said Dr. Atsuhiko Isobe, who is a professor at Kyushu University's Research Institute for Applied Mechanics, and a co-author on 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."
Microscopic image of microplastic samples gathered from the oceans for the study. Pieces less than 5 millimeters (0.20 inches) in diameter are classified as microplastics. Scale bar: 2000 micrometers/2 millimeters (0.08 inches). (Credit: Kyushu University/Asahi Kasei Corporation)
For the study, the researchers estimated the ages of microplastics by analyzing their ultraviolet (UV) exposure, plastic oxidation levels, and ambient (surrounding) temperature, finding that UV exposure and ambient temperature were the primary factors in the degradation of microplastics.
In the end, the study’s results determined microplastics closer to the coastlines, known as nearshore regions, exhibited age ranges between 0 to 5 years old, while microplastics farther away from the coastlines, known as offshore regions, exhibited age ranges between 1 to 3 years old.
Study co-author, Dr. Atsuhiko Isobe and the crew using a net to collect microplastic samples from the upper oceans for the study. (Credit: Kyushu University/Isobe Lab)
Study co-author, Dr. Atsuhiko Isobe, gathering recnetly-collected microplastic samples from the upper oceans. (Credit: Kyushu University/Isobe Lab)
Study lead author, Dr Rie Okubo, analyzing collected microplastic samples under a microscope. (Credit: Kyushu University/Asahi Kasei Corporation)
"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," said Dr. Rie Okubo, who is a researcher at Asahi Kasei Corporation, and lead author of the study. "These offshore microplastics are also likely removed from the upper oceans by settling deeper into the waters."
Going forward, the researchers hope the methods used and data gathered in this study will offer greater clues as to how microplastics both form and propagate throughout the environment, along with constructing better models to help track microplastics throughout the ocean, as well.
What new discoveries will researchers make about microplastics and their impact on the ocean in the coming years and decades? Only time will tell, and this is why we science!
Sources: National Oceanic and Atmospheric Administration, Santa Cruz Works, Marine Pollution Bulletin, Kyushu University
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