The sun's UV light slowly degrades plastics on the ocean's surface.
Floating microplastic is broken down into ever smaller, invisible nano plastic particles that spread throughout the entire water column, as well as compounds that bacteria can then completely degrade.
Experiments at the Royal Netherlands Institute for Sea Research, NIOZ, on Texel demonstrated this.
Ph.D. student Annalisa Delre and colleagues calculated in the latest issue of the Marine Pollution Bulletin that about 2% of visibly floating plastic may disappear from the ocean surface in this manner each year.
The Plastic Paradox
Anastasia Nelen/Unsplash
Since the mass production of plastics began in the 1950s, a significant amount of plastic waste has made its way to the ocean via rivers, winds blowing off land, or ships directly dumped.
However, the amount of plastic found in the ocean is only a fraction of what has entered the ocean.
The vast majority has been lost, as per ScienceDaily.
This is known as the Missing Plastic Paradox in science. Delre and colleagues conducted laboratory experiments to see if UV light degradation could explain some of the vanished plastic.
The researchers mixed small plastic pieces in a container filled with simulated seawater. They then automatically stirred this plastic soup under a lamp that mimicked UV light from the sun.
Gases and dissolved compounds, including nano plastics, were then captured and analyzed as they leached from the degrading plastic pieces.
The researchers calculated that at least 1.7% of (visible) microplastics degrade each year based on these measurements.
For the most part, it degrades into ever smaller pieces, including (invisible) nano plastics and molecules found in crude oil.
Bacteria may be able to break down some of these further.
Only a small portion is completely oxidized to the relatively innocuous CO2.
Many people have seen photos of larger plastics entangling marine life, whether it's a sea turtle caught in a plastic six-pack ring or a dolphin entangled in plastic fishing gear, as per Woods Hole Oceanographic Institution.
While the effects of larger plastics are well understood, little is known about the health effects of microplastics.
Microplastics are consumed by marine organisms at the bottom of the food chain, such as plankton and fish larvae, and filter-feeding animals that humans eat, such as oysters and scallops, ingest the particles as they filter seawater.
Plastics may pose a risk to both marine animals and humans because they may contain toxic chemicals used in the manufacturing process such as phthalates, bisphenol A, and others.
These additives can alter the properties of plastic items in a variety of ways. They may, for example, make water bottles more rigid and pens more flexible.
Plastics can also become toxic by absorbing harmful chemicals from the environment, such as polychlorinated biphenyls (PCBs), which have been linked to cancer and other serious human health issues.
Scientists are investigating the potential health risks posed by microplastics to marine life and humans by determining which types appear to be the most toxic and how much of those are consumed by marine animals.
