A new type pf bioaccumulation

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Small plastic chips can be eaten by fish, which often are eaten by bigger fish, birds or other predators. (Photo by Mike Schoonveld)

Some say the “environmental movement” started in 1962 when Rachel Carson’s tome, Silent Spring, was published. Whether it started there or whether the book only added fuel to struggling fire, really doesn’t matter. What it did is bring the concept of bioaccumulation into the lexicon used by ordinary, nature-loving people, not just scientists squirreled away in rooms full of test tubes and microscopes.

For the few of you unfamiliar with the word, it has to do with how toxins present in teeny, minuscule doses in the environment can be concentrated through the food chain leading to harmful levels of these substances in organisms far up the food chain.

DDT was one of the most effective insecticides ever developed. It was inexpensive, very effective in killing insects, easy and realistically, quite safe for humans to use. Plus, and this is the biggy, it was persistent. Sprinkle a little DDT around the house (or in the garden or over an entire swamp full of mosquitoes) and the house stayed roach-free, the tomatoes were rid of tomato worms all summer and the mosquitoes were controlled in the swamp for a long time. The DDT didn’t break down or evaporate.

What it did, and what Carson reported on in Silent Spring, was wash into rivers and lakes in infinitesimal small concentrations and became absorbed into the tiniest creatures in the food chain. Not much got into them, perhaps only a molecule or two – let’s say just one.

What happens next? DDT molecules aren’t digested and excreted or even changed by digestive processes. Instead they are stored in fat cells. So now, let’s say, the next predator up the food chain, say freshwater shrimp eats 1,000 zooplankton each with one molecule of DDT. The DDT gets stored in the shrimp’s fat cells but the shrimp now has a thousand times more DDT in it than the tiny plankton did.

Minnows eat freshwater shrimp and if, in it’s lifetime, the minnow eats 1,000 shrimp, do the math. It contains a million molecules of DDT. Continuing with the math, let’s say a perch eats 1,000 minnows and ends up with a billion DDT molecules. Then a walleye eats a 1,000 perch and ends up with a trillion molecules. Then a peregrine falcon or bald eagle gets a good dose of DDT with every big fish it eats.

That’s bioaccumulation. Now there’s a new kind of bioaccumulation, suspected, but only recently discovered.

A few years ago a scientist gathered a bunch of baby cormorants then sacrificed them in the name of science so he could study them, checking for gene mutations.

Afterwards, the test “cormlets” were stored in a freezer until a Canadian scientist decided to thaw them out and check their stomach contents for micro-plastics and other “foreign” contents. Micro-plastics are to plastic as sawdust is to wood. Twenty-six of 30 specimens checked had  man-made debris such as microplastics, fibers from clothing, paint, synthetic leather and glass in their stomachs.

Cormorants only eat fish, unlike fish which occasionally mistake microplastic, fibers and other things for bugs or other edibles and eat them. Baby cormorants only eat partially digested fish brought to them by their parents. The glass and plastic don’t digest, so the babies actually get a dose of indigestible debris with each feeding, possibly getting more than their parents started with. A new kind of bioaccumulation is occurring.

Other than clogged digestive systems in a few individuals, thus far, no definitive connection between fish or animals eating plastic and disease or poisonings has been made. That doesn’t mean animals accidentally eating plastic are okay or should be ignored.

It means humans – the source of everything plastic – should be aware and do what they can to keep unwanted, discarded or used plastic out of the environment. Recycle as much as possible and responsibly dispose of what plastic can’t be recycled.

 

 

Categories: Michigan – Mike Schoonveld

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