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      NPR 2019-03-29

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      Dozens Of Nonnative Marine Species Have Invaded The Galapagos Islands

      AUDIE CORNISH, HOST:

      The Galapagos Islands are like a biological ark in the eastern Pacific Ocean. There are giant tortoises and swimming iguanas and numerous creatures found nowhere else. It's one of the world's most protected places. But scientists have discovered that dozens of exotic species have invaded the Galapagos - underwater. NPR's Christopher Joyce reports on this unexpected finding.

      CHRISTOPHER JOYCE, BYLINE: Marine biologist James Carlton remembers when he first got to thinking that the Galapagos Islands may not be as pristine as people thought.

      JAMES CARLTON: On my first visit to the Galapagos, I collected some samples from a boat bottom.

      JOYCE: Barnacles, sponges and other hitchhikers. That was 1987. Carlton didn't know if those creatures he found were native or not, so four years ago, he and a team of scientists decided to return and take a closer look.

      CARLTON: We didn't know quite what to expect.

      JOYCE: What they did know was that on land there were lots of invasive species, species that are not native to the islands. But in the surrounding ocean, scientists only knew of five invaders; everything else presumably was native. When Carlton's team looked underwater, however, they found a horde of invaders.

      GREGORY RUIZ: And now we have 53, which is a rather stunning increase.

      JOYCE: Marine biologist Gregory Ruiz says they found exotic species on pilings, docks and mangrove roots. They hung plastic plates underwater, and all sorts of alien invertebrates latched onto them. At the Smithsonian Environmental Research Center in Maryland, where he works, Ruiz shows me the invasions lab. Researchers here track invasive species around the world.

      RUIZ: This is a organism that we found in the Galapagos.

      JOYCE: Tunicate.

      RUIZ: It's a tunicate.

      JOYCE: Also known as a sea squirt, a tiny tube-like animal. He has more invaders in glass bowls filled with alcohol - barnacles, algae, sea anemones. They're described in the journal Aquatic Invasions. Ruiz says rising tourism in the Galapagos means more boats, docks and pilings - transportation and homes for invasives. These organisms aren't just footnotes in a biology text. Zebra mussels invaded the Great Lakes and caused havoc. The tiny parasite called MSX has killed millions of oysters in the Chesapeake Bay on the East Coast.

      James Carlton, now professor emeritus at Williams College, says tracking invaders helps authorities stem their spread. He expects other tropical areas are heavily invaded as well. And in a protected place like the Galapagos, he says, their presence means something's been lost.

      CARLTON: We value a world that we think represents nature before we began altering it, before we began removing species, adding species and changing the abundance of species.

      JOYCE: Even in the Galapagos, that world is disappearing. Christopher Joyce, NPR News.


      內容來自 VOA英語學習網http://www.tg377.com/show-8753-241572-1.html
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