As officials plan a cleanup of the foul Matanza-Riachuelo River Basin, in Buenos Aires scientists are awed by the handful of creatures that manage to survive there.
BUENOS AIRES — The hyper-polluted Matanza-Riachuelo River Basin in Argentina has the dubious distinction — alongside the likes ofChernobyl — of being one of the world's 10most toxic sites.
And yet somehow, someway, certain animals manage to survive in this "wetland," where decomposition of organic matter through microorganisms sucks up the water's oxygen. Wildlife observed in the basin include carnivorous turtles, coypus (river rats), herons and other native birds.
The area absorbs the untreated sewage of some 6 million Buenos Aires residents, many living in ramshackle housing without sewerage, as well as factory chemicals. How is it, then, that some creatures remain? Good question, say scientists, who aren't yet clear if the surviving rodents and reptiles are "clinging to life" or evolving to deal with their toxic reality.
For insight, Gabriel Ciacobone, a zoologist working with the city government, is studying the area's turtles. "Tortoises are living fossils, animals that have tolerated everything, from radiation to pollutants," he says. They also breathe air, which is important, since there is little to no oxygen left in the river and surrounding wetlands.
Measurements by municipal researchers have shown the waters to have between 0 and 1 mg of oxygen per liter. Fish generally need twice as much to live, and a healthy river should have between 5 and 7 mg oxygen/liter. There are no fish, therefore, in the Matanza-Riachuelo, meaning that for sustenance, tortoises must snap up other delicacies, like birds.
The Buenos Aires city government is planning a cleanup of the area that is expected to cost millions of dollars and take decades to complete. In the meantime, municipal boats monitor the waters, where recreational navigation is banned.
In the most polluted part of the wetlands, the enclosed Cildáñez stream, government scientists are testing the stomach contents of some of the big tortoises. No doubt there are clues to be gleaned from dissecting their diets. But there's still the question how the reptiles can actually live in the toxic sludge. Or how they can stand to drink it!