单项选择题

More artificial reefs (礁石) are being lowered into the ocean now than ever before. But as artificial-reef initiatives grow to include more coastal regions and a wider (62) of aged infrastructure(基础设施),some scientists worry that the commercial interests of fishing, diving and trash (63) are driving efforts that should be environmental. (64) that’s the case, they warn, (65) reefs may ultimately give way to an underwater junkyard. " (66) it’s one of these things where people take a very (67) view-drop something in the water and a bunch of fish come and that’s wonderful," says Bohnsack, a fisheries biologist. "The reality is not so simple. "
Do man-made reefs (68) ecosystems that have been destroyed by pollution, over fishing and global warming Or do they merely attract existing populations away from natural habitats (栖息地), concentrating them (69) unnatural ways and making them more (70) to over fishing "In a lot of cases, that question has been answered," says Bohnsack. "But supporters of reefing aren’t too happy with the answer, so they (71) it." Research shows that artificial reefs only (72) fish populations when habitat is the limiting factor. In many cases, it isn’t. Over fishing is the bigger crinunal, and artificial reefs only make the problem (73) .
Not everyone agrees. By (74) fishing restrictions, reef coordinators say they can (75) against the overfishing of vulnerable species. They believe the overfishing issue is manageable.
(76) , there’s the question of safety and durability. The government is still cleaning up an ill- fated 1970s attempt at artificial reefing that employed more than 2 million tires (77) together with weak metal clips off the coast of southern Florida. The tires came (78) from one another during a rash of (79) storms. Since then, they have been (80) around the ocean floor, destroying natural reefs, polluting the water and occasionally washing (81) on shore.