“Oh, what a tangled web we weave, when first we practice to
deceive pollute.” I know it doesn’t rhyme. But the tangled web is real:
Songbirds feeding near the contaminated South River are showing high levels of mercury, even though they aren’t eating food from the river itself, according to a paper published by William and Mary researchers in the journal Science.
Lead author Dan Cristol said his paper has wide-ranging international environmental implications. Mercury is one of the world’s most troublesome pollutants, especially in water. The South River, a major tributary of Virginia’s Shenandoah River, has been under a fish consumption advisory for years, as are some 3,000 other bodies of water in the U.S.
The paper shows high levels of mercury in birds feeding near, but not from, the South River. Cristol and his colleagues also identify the source of the pollutant–mercury-laden spiders eaten by the birds. The Science paper is one of the first, if not the first, to offer scientific documentation of the infiltration of mercury from a contaminated body of water into a purely terrestrial ecosystem. (Science Daily)
Inorganic mercury was dumped into the river between 1930 and 1950. Bacteria then converted it to the more toxic organic methyl mercury. Aquatic animals low in the food chain were eaten by predators higher up, biomagnifying the concentrations. So any person or animal eating stuff from the river would be at risk of effects from mercury. The levels in food fish were so high that eating them is forbidden. This is quite common now in US rivers because of mercury pollution.
The songbirds studied by the William and Mary scientists weren’t eating the fish. Songbird parents feed songbird babies little spiders with high levels of mercury. The question still remains: how did the spiders get the mercury? We have yet to learn that important link in the chain.
Meanwhile, though, Darwin’s “tangled bank” has also become a tangled web of pollution.
“It is interesting to contemplate a tangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent upon each other in so complex a manner, have all been produced by laws acting around us.” (Darwin, Origin of Species)