The waters around the Galapagos Islands, a hot spot of biodiversity off the coast of Ecuador, have been invaded by more alien species than previously thought.
While the number of invasive species on land is well-documented, relatively little was known about those in the marine environment.
Now field surveys have found 48 invasive species off the coasts of the islands, in addition to five known non-native species. These creatures probably got a free ride on ships from around the world.
These surveys were undertaken only in certain hahitats around two of the larger islands, so the actual number of invasive species is likely to be much greater. “From our knowledge of similar studies, I wouldn’t be surprised if the number was twice as many,” says team member Jim Carlton of Williams College in Massachusetts.
The alien species included worms, mussels crabs and sea squirts. There were also tiny moss (苔藓)animals, such as Amathia verticillata, which kills seagrass and messes up fishing equipment.
Seventeen of the newly-identified invaders had been spotted around the Galapagos Islands before, but bad been wrongly thought to have been native species.
The influence of these alien species on the islands’ ecosystems is not yet known. But it is likely to be damaging judging from experiences elsewhere, and could threaten hundreds of local species on the islands. “What we know is that a number of these invasive species clearly have had serious effects elsewhere in the world,” says Carlton.
Invasions in other places suggest that even more harmful species could soon be headed for the waters of the Galapagos Islands, the team warns, including soft corals (珊瑚虫)that could grow rapidly over local coral, and the possibility of poisonous lionfish crossing from the Caribbean through the Panama Canal.
The Galaparos Marine Reserve is now protected, but it will be hard to stop further invaders because it is difficult to check for tiny species on the bottom of every visiting boat.
8. How many invasive species have been found off the coasts of the Galapagos Islands?
9. What can be learned about Amathia verticillata?
A.It mainly feeds on worms and lionfish. |
B.It’ll be harmful to the fishing industry. |
C.It was the earliest invader found in Ecuador. |
D.It makes up the majority of invasive species. |
10. What’s the seventh paragraph mainly about?
A.The damage of local species. | B.The ecosystem around Ecuador. |
C.The impact of invasive species. | D.The number of invasive species. |
11. Why is it difficult to prevent further invasion?
A.Alien species are spreading quickly. | B.Many ships visit the islands illegally. |
C.It’s hard to identify very small species. | D.There is a lack of men needed for the job. |