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Choose your poison

发布时间:2019-03-08 05:10:15来源:未知点击:

By Fred Pearce SHELLFISH in the North Sea have recovered dramatically since small boats were banned from using antifouling paints containing tributyltin (TBT). But a British scientist warns that extending the ban to large vessels could do more harm than good. Antifouling paints are applied to the hulls of boats to kill barnacles. Countries bordering the North Sea banned the use of TBT paints on small boats during the 1980s after marine biologists revealed that tiny amounts of the chemical dissolving into seawater can damage marine molluscs. Problems include sterility and a condition called imposex, in which females grow a rudimentary penis. The damage was worst around marinas, harbours and estuaries. By the mid-1990s, with TBT still in use for larger ships, imposex was taking hold in the North Sea and some scientists were forecasting that whelks would become extinct there unless there was a total ban. Last year, the UN’s International Maritime Organization agreed to ban the use of TBT on commercial shipping worldwide. But now researchers at the Dove Marine Laboratory at the University of Newcastle upon Tyne report a revival of North Sea whelks. The number of whelks landed at fishing ports tripled between 1992 and 1997. Andy Birchenough told a meeting of North Sea researchers at the university last month that they are now abundant on the coasts of Britain, Norway and France. “Symptoms of imposex have decreased dramatically,” says Stewart Evans, the laboratory’s director. He agrees that the main cause of the revival was the TBT ban. But he opposes its extension. “It should wait until we have done sufficient research to know that the alternatives won’t do even more environmental harm,” he says. One leading alternative, Irgarol 1051, made by the Swiss-based chemicals company Ciba, is widely found today in European coastal waters, and “already appears to be causing harm”, says Evans. “Off the west coast of Sweden it is associated with the death of phytoplankton.” But Ciba says its studies suggest the chemical doesn’t persist in the environment. Other alternatives contain copper, which can also be toxic to marine life at high concentrations. Evans sees some benefits from sticking with TBT for large ships as it is still the most effective antifoulant. And he thinks fouled ship hulls may carry alien species into new habitats. “Ireland never had any invasions of marine species until they stopped using TBT,” he says. But many environmentalists disagree. Sian Pullen, marine expert with the British arm of the Worldwide Fund for Nature, says: