ENVIRONMENT

The sea is awash with microscopic bits of plastic. But a hint of good news is emerging from Vancouver Island, where a recent investigation found that the amount of plastic contamination in shellfish there is just a tiny percentage of what the scientists expected. (Hakai Magazine)

Take these 10 easy steps to fight plastic pollution.

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Discussion Ideas

• The new study was partly funded by the British Columbia Shellfish Growers’ Association. What are shellfish?
  • Shellfish is a general term for an aquatic animal that has a shell or exoskeleton. Shellfish include crustaceans (such as crabs, shrimp, and lobster), shelled mollusks (such as clams, oysters, and snails), and cephalopod mollusks (such as octopus, squid, and cuttlefish). (Yes, you read that right: squishy cephalopods are really shellfish.)
  • In this study, scientists studied clams and oysters at about 20 sites around Vancouver Island, British Columbia, Canada. The sites included shellfish in both aquaculture and wild locations.

 

• The new study measured the amount of microplastics clams and oysters. What are microplastics?
  • Microplastics are just what they sound like—tiny plastic particles no more than 5 millimeters in diameter.

 

• Why are clams and oysters such good indicators of the presence of microplastics in marine ecosystems?
  • Like most bivalves, clams and oysters are filter feeders. Oysters, for instance, use hair-like organelles called cilia to constantly draw seawater over their gills. Microorganisms suspended in the seawater provide nutrients to the oyster.
    • Microorganisms filtered into the oyster might include nutrient-rich plankton and algae, but also pollutants such as plastics, fertilizers, and even excess sediment. According to the good folks at New York-New Jersey Baykeeper, an adult oyster can filter as much as 50 gallons of water a day. (!)
    • Filter feeders are often considered indicator species in marine ecosystems, because they are sensitive to the tiniest change in the environment.

 

• One scientist involved in the new study said he anticipated finding hundreds or even thousands of microplastics in each oyster or clam. Why did scientists expect to find such heavy concentrations of plastic in Vancouver Island’s shellfish population?
  • lots of precedent. Local scientists previously found extremely high concentrations of microplastics in both the seafloor sediments around Vancouver Island, and in the shellfish themselves.

 

• The latest study reported less than one instance of microplastic in each oyster or clam. Why are the new results so different than those in previous studies?
  • Scientists aren’t sure. Some ideas worth pursuing:
    • different sites. The different results may simply be the results of different shellfish sites. Tides, seasonal variation, ocean currents, and changes in local human activity could all impact results.
    • microplastics vs nanoplastics. Earlier research investigated much smaller pieces of foreign material than the current study. Shellfish in the current study could have much higher concentrations of plastic, but scientists were uncomfortable conclusively identifying such tiny fragments.
    • misidentification. Perhaps the most intriguing part of the new study was the identification of foreign material. When examined under a microscope, many substances tentatively identified as plastic turned out to be fibers such as cotton and rayon. The fibers may have gotten into the samples through the oysters’ filter feeding or through contamination by “particles shed from researchers’ clothing.”

 

• So, are we overestimating the problem of plastic pollution in the ocean?
  • NO. Just, no.
    • Even natural fibers such as cotton, researchers remind us, can be pollutants. They can carry pesticides and other substances that are toxic to shellfish.
    • Plastics are polluting the ocean. “A 2017 report from the International Union for Conservation of Nature concluded that 1.4 million tonnes of microplastic are dumped into the ocean per year—the equivalent of one plastic grocery bag for every person on the planet each week.”
    • Planet or plastic? Join National Geographic’s campaign to reduce plastic pollution in the ocean.

 

TEACHERS TOOLKIT

Hakai: Some Plastic Pollution Isn’t Plastic After All

Nat Geo: 10 Ways to Beat Plastic Pollution

Nat Geo: Ocean Plastic resource collection