Changing Planet

More Plastic, Fewer Oysters?

Co-authored by Erica Cirino

2016 started off with a dire prediction for the world’s oceans: By 2050, the seas will contain more plastic—by weight—than fish. There’s an estimated 8 -12 million metric tons of plastic making its way into the oceans each year. And as the plastic mess in the oceans grows, so do concerns over the health of the marine creatures living in it.

While it’s known that plastic bags and bottles pose a risk to sea creatures, a lesser-known threat is now coming to light, one that’s created when ocean waves and wind pulverize the plastic bags, bottles and other trash that ends up in the seas: “microplastics.”

These tiny plastic pieces are about the same size and shape as the algae eaten by some marine animals. How microplastics affect marine animals is not well understood.

Microplastic poses a growing concern in oceans and other aquatic habitats. (Image by 5Gyres, courtesy of Oregon State University)

But in recent years scientists have found that crustaceans that consume microplastics have a hard time reproducing. Going off a hunch that microplastics may affect the fertility of other filter feeders, researchers at the French Institute for the Exploitation of the Sea started feeding oysters microplastics.

The researchers observed two groups of oysters: one fed a normal diet of algae and another fed a mix of algae and microplastics. The oysters fed the mixed diet swiftly sucked up the microplastics as easily as they did algae. After two months the researchers have found microplastics take a toll on both oyster digestion and reproduction.

Oysters that consume microplastics eat more algae and absorb it more efficiently, says Arnaud Huvet, marine physiologist at the French research center and lead author of the study. This is because oysters expend extra energy to pass plastic through their digestive systems, increasing the rate at which they digest algae.

While the digestion of microplastics diverts some energy away from reproduction, oysters’ ability to reproduce is almost halved: Female oysters produce fewer and smaller eggs while male oysters produce slower-swimming sperm. Offspring produce more slowly. The cause? Blame the chemicals that make up microplastics.

During digestion microplastics appear to leach hormone-disrupting chemicals into oysters’ bodies, says Huvet. These chemicals, also called “endocrine disruptors,” are known to lead to diminished fertility and an increased cancer rate in laboratory animals, wildlife and humans. They’re found in all kinds of everyday products, including cosmetics, pesticides and plastics.

Can the microplastics accumulating in oysters’ bodies harm the animals or humans that eat them? Right now, Huvet says, that’s unclear. But he points out his study adds to a slowly growing body of evidence highlighting the health impacts of plastic pollution in the oceans.

Safina Center Sustainable Seafood Program Director Elizabeth Brown-Hornstein agrees: “This study provides further evidence that plastic litter has far-reaching effects on the oceans and that there is an urgent need to take meaningful action to tackle this issue.”

Learn more about plastic and other marine pollution, and what you can do to help, here.

Ecologist Carl Safina is author of seven books, including the best-selling “Beyond Words; What Animals Think and Feel,” and “Song for the Blue Ocean,” which was a New York Times Notable Book of the Year. His writing has won a MacArthur “genius” prize; Pew and Guggenheim Fellowships; book awards from Lannan, Orion, and the National Academies; and the John Burroughs, James Beard, and George Rabb medals. His work has been featured in The New York Times, The Los Angeles Times, The Washington Post, National Geographic, and elsewhere, and he hosted the 10-part “Saving the Ocean” on PBS. Safina is founding president of The Safina Center at Stony Brook University.
  • Jessica Perelman

    Dear Mr. Safina,

    In light of the growing apprehension regarding ocean pollution, this is a fantastic piece that sets up a strong foundation for addressing the damages caused by microplastics. Currently in my final year of study as an undergraduate biology student, I am shocked and intrigued by the massive amount of plastic reportedly circulating the oceans. However, considering the broad range of products from which this pollution originates, it is no shock to me that tiny plastic particles can accumulate to such quantities as 93-236 thousand tons floating in the oceans as predicted by a recent study in Environmental Research Letters. It concerns me that this amount is 37 times greater than previous estimates because it speaks to just how much more abundant these pesky products are, and how much of an impact they can realistically have on marine wildlife. You address the harm that consumption of microplastics has had on crustaceans and other filter feeders, and it seems that adding microplastics to the diet of oysters proves that this can have repercussions on a number of marine organisms. As reiterated from the study by the French Institute for the Exploitation of the Sea, “Oysters that consume microplastics eat more algae and absorb it more efficiently…[their] ability to reproduce is almost halved.” This information you present is valid and credible, but should there be further emphasis in the post regarding the seriousness of these health implications? Filter feeding organisms are vital components of marine food webs, and their demise could mean severe threats to numerous trophic levels, and in turn to the humans who rely on these species as a source of food.

    This past December, President Obama signed a bill banning the use of microbeads in all personal care products. This act is an indication that microplastic pollution is a genuine concern to the highest levels of government and will continue to damage aquatic habitats and waterways if preventative action is not taken immediately. Your article additionally mentions that the chemicals comprising microplastics are to blame for reproductive complications in oysters, which is a very important point to address. Chemical toxins such as DDT and BPA have been found to adhere to microplastic particles according to a Global Microplastics Initiative, which then “enter the food chain when ingested by aquatic life, accumulating in birds, fish, marine mammals and potentially humans.” Could there be further implications of such chemicals to the well being of this broad range of organisms? How else might the toxins and accumulation of microplastics affect marine species? Since microplastics have already been found inside the bodies of so many organisms, it would be beneficial to address some of the effects they can have on these various other animals as well, so that readers outside the scientific community can have a better understanding of the issue as a whole. That being said, your article is extremely informative and acknowledges the use and waste of plastic products as a matter of high priority. I am interested to hear your thoughts and opinions as attempts to mitigate the problem continue to develop.

  • Lowell

    Thank you, Carl, for your work.

    We just don’t listen, to our planet, to our experts, to our consciences. In my opinion, it’s time to stop eating seafood completely, and let the ocean fix itself, as it certainly will, once we stop our endless greed-fueled exploitation of sea creatures and plants.

    Pollution is another matter, but we can all personally affect the health of the sea by just stopping our consumption of it’s resources.

    Lowell H.

  • Pingback: 'Mermaid's tears': the terrifying scale of microplastic pollution | GeoIssues()

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