Environmental▼News trations in the air over the Great Lakes roughly every six years, Buehler says. The increase was especially noticeable in 1998 and 1999, Hites adds. The findings raise a lot of questions about what could be causing the blip in PCB concentrations, says Keri Hornbuckle, an environmental engineer at the University of Iowa. Dredging of PCB-contaminated lake sediments has increased significantly in recent years, and PCBs could be evaporating into the air
when sediments are dumped on the shore to dry before transport, she says. Brownfield remediation, sediment disturbance by storms, or changing weather patterns are also potential culprits, adds Melissa Hulting, an environmental scientist with the U.S. EPA’s Great Lakes National Program Office. Although production and most uses of PCBs have been banned in the United States and Canada, Buehler’s findings show that governments still need to do some-
thing about existing sources, including old electrical transformers, some of which are still allowed to be used, and landfills, Hulting says. Decommissioning of old PCB-laden electrical transformers is now voluntary but is encouraged by the agency. EPA is working on a national action plan for PCBs that includes remediation of polluted sites, but the agency has not decided if it should create a new rule to mandate decommissioning of old transformers, she says. —JANET PELLEY
tides and waves. “The true economic value [of seagrasses] is difficult to measure, but this work suggests it is immense,” says Ed Green, one of the book’s 58 coauthors. According to the Atlas, seagrasses occupy an area of 177,000 square kilometers worldwide, around twothirds the size of Great Britain, but this is 15% less than the coverage of only 10 years ago. Fishing gear, anchors and propellers, land reclamation and coastal development schemes, and ecotourists can all cause damage to seagrasses. In some places, such as the Baltic Sea, sewage and chemical effluent encourage the growth of seaweeds that smother seagrasses, according to the Atlas. The 15% decline “is a very significant, very worrying finding,” said Ken Collins from the Southampton University’s oceanography center in
the United Kingdom. “The problem is that seagrasses are very fragile. In the Mediterranean Sea, for example, illegal trawling is tearing them up. There is concern because they are a key habitat. They are nursery grounds for a huge number of fish species and an important staging post in the life cycle of many commercial fish species.” In addition to raising awareness about the problems faced by seagrass, the Atlas trumpets some solutions. For example, coauthor Fred Short applauds the new $1 billion sewage processing system in Boston Harbor, which has encouraged seagrasses to return for the first time in 200 years. For more information about the Atlas, go to www.unep-wcmc. org/marine/seagrassatlas. The World Atlas of Seagrasses is available from www.ucpress.edu/books/ pages/10168.html. —MARIA BURKE
Seagrasses under threat The first global survey of the world’s seagrasses shows that the fragile aquatic plants are declining around the globe. Like coral reefs, the seagrasses are threatened by sewage effluent and coastal developments. Seagrasses are flowering plants that live in coastal waters from the Arctic to the Tropics. According to the World Atlas of Seagrasses, they provide food and shelter for many animals, including endangered manatees, dugongs, turtles, and sea horses. They are also nursery grounds for commercially important species, such as salmon, scallops, and crab. The Atlas, which was released on October 17, points out that seagrasses often protect coral reefs by filtering sediment and nutrients from the water. Seagrass roots also protect coastal resources by slowing the erosive impact of
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