Those "pristine" Charleston estuary waters are in worse shape than most people think. At least 7 1/2 tons worse.
That's how much plastic is estimated to be breaking down in the tide and waves of Charleston Harbor, its tidal rivers and creeks. The total comes from a study by a research team from The Citadel. The assessment doesn't even begin to gauge how much of that plastic already has come apart into microscopic fragments, fibers and balls.
Sooner or later, a portion of that waste gets eaten by marine critters such as shrimp. It can kill them, or be eaten in turn by you.
The disturbing finding joins earlier studies by the College of Charleston and others that discovered among other things:
Microfibers from synthetic clothing in oysters.
Antibiotic resistance in dolphin from exposure to antibiotics.
Some of the worst concentrations of flame retardants in dolphin that have been found; half the dolphin tested weren't healthy.
Stain repellents in loggerhead turtles in levels that weaken the immune system.
Nobody knows yet how far the wastes degrade water quality or human health, but troubling studies of the impact on marine life are starting to emerge. The Citadel estimate came from studying the plastics retrieved from various points around the harbor during annual river sweeps.
"It is surprising," said physiology Prof. John Weinstein. "When you think of it, our plastics don't weigh that much. So imagine 15,000 pounds, that's a lot of plastic. Each water bottle is going to fragment into thousands of particles, so 15,000 pounds, think of how many particles that is."
In a novel experiment as part of the project, Cadet Brittany Crocker, 21, is studying samples of three common kinds of plastics placed in the marsh to see how quickly they degrade. A similar field study hasn't been done before, as far as she and Weinstein know. The results so far are discouraging.
The plastics degrade even slower than expected. Within four weeks, a biofilm develops over them that "acts like a sunscreen," she said, to slow the process down.
And in another aspect of the study, Weinstein has found that shrimp gobble down the microspheres, those tiny plastic balls. "They'll eat them like popcorn, pop them in and fill their gut." The largest fragments get spit out, the smallest get passed through, but the mid-range size kills them within 48 hours.
The study and a complementary study were fund by the S.C. Sea Grant Consortium.
The microspheres are as small or smaller than humans can see. They are manufactured and found in products from toothpastes to facial scrubs.
"It's opened my eyes a lot," Crocker said. "A facial scrub that I used to clean my face with, to find they're microspheres that could have this effect in the ocean - it blows my mind to think they could have this impact on the environment. Most people don't know that. Most people, when they put it down the drain, don't think about it anymore."
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