From the remote peaks of the French Pyrenees Mountains to the depths of the Mariana Trench to the human body, the modern world is awash in plastics. In the oceans, a portion of the estimated 8 million metric tons of plastics that humanity dumps into the sea each year ends up as food for unlucky sea creatures.
The bigger chunks can clog the digestive systems of turtles, seabirds and whales, causing them to starve to death, while the tiniest and most insidious bits can be taken up by plankton, infiltrating the very foundation of the ocean food chain.
Now, researchers have discovered an unexpected way that larger bits of plastic are transformed into microplastics in the sea: lobsters. The new study found that when the deep-sea Norway lobster consumes plastics, its body grinds them up into even tinier pieces that are likely released back into the ocean in its excrement, reports Liz Allen for Forbes.
By breaking down these already miniscule bits of plastic into even more minute pieces, the lobsters are making it possible for even smaller creatures to mistakenly eat them and experience their potentially harmful effects.
Besides causing starvation, plastics may also leach dangerous chemicals over time, such as phthalates and bisphenol A. The effects of these chemicals on human and environmental health are concerning to scientists, but it’s not yet clear whether plastics are shedding these harmful chemicals in significant quantities to hurt people and animals, reported Chris Joyce of NPR in 2018. One recent study found that microplastic fibers, one of the most common forms of microplastic, can cause aneurysms as well as harmful respiratory and reproductive changes in fish.
Apart from the noxious chemicals within plastic, it also acts like velcro when it comes to other toxic contaminants. PCBs, for example, have been detected in high levels within tiny ocean crustaceans called amphipods that had consumed plastics.
Lobsters are scavengers; they roam the seafloor the world over searching for dead things and other bits of food that have drifted down from the surface. Unfortunately, the seafloor has become a clearinghouse for plastics.
To see what happens when lobsters ingest plastic, researchers gathered Norway lobsters (Nephrops norvegicus) from the Mediterranean Sea near Sardinia. Previous research into the consumption of plastics by crustaceans has shown that larger pieces of plastic became lodged in the lobsters’ stomachs, but smaller pieces were pulverized into even tinier pieces by a part of the lobster’s digestive tract called the gastric mill, the researchers report last month in the journal Environmental Science & Technology.
Crustaceans like the Norway lobster use their gastric mill in lieu of teeth, which they lack. The mill is composed of hard, calcified plates that crush the animal’s food like a mortar and pestle, reports Nick Lavars for New Atlas.
These smaller plastic fragments are then likely released into the surrounding deep sea environment by the lobsters through their feces, the researchers report. Identifying lobsters and other crustaceans as potential sources of nanoplastic (the technical term for plastics smaller than a micron) worries scientists, since plastics of that size may actually be incorporated into the tissues of the animals that consume them instead of simply stuck in their guts.
“These findings highlight the existence of a new peculiar kind of ‘secondary’ microplastics, introduced in the environment by biological activities,” the authors write, “which could represent a significant pathway of plastic degradation in a secluded and stable environment such as the deep sea.”