A notorious class of environmental contaminants appears to be increasing in the open ocean despite regulations, according to a new study. Researchers say the trend is threatening endangered bird species and potentially humans as well.
Humanmade chemicals such as PCBs and DDT--typically used as pesticides and industrial coolants--can disrupt the endocrine system of humans and other animals, causing reproductive and immunological disorders. Transported by rivers and winds, these pollutants usually end up in the world's oceans. The 1963 Clean Air Act and 1972 Clean Water Act restricted the use of PCBs and DDT in the United States, and some studies have reported declines of contaminants in marine predators that live in estuaries and coastal areas near shore.
To see if PCB and DDT levels had also dropped in larger expanses of open oceanic zones, Myra Finkelstein, an ecologist at the University of California, Santa Cruz, and her colleagues measured the presence of these pollutants in two species of albatross. Both the endangered black-footed albatross and the Laysan albatross are able to cross 1500-kilometer-wide ocean basins when searching for dinner. The team used satellite tracking to map the birds' feeding routes and sampled blood from 26 black-footed and 16 Laysan birds to compare contaminant levels.
Both kinds of birds have more pollutants in their blood than they used to. Levels of DDT and PCBs were twice as high in Laysan albatross as they were 10 years ago, and DDT levels were four times higher in black-footed's, the team reports 6 April in Ecological Applications.
In addition, Finkelstein's group found that black-footed albatrosses, whose range extends from the West Coast of North America to Hawaii, had three to four times higher levels of PCBs, DDT, and mercury than the Laysan albatrosses, which forage near Alaska and the Aleutian Islands, perhaps indicating higher levels in the black-footed's domain. The differences could also be due to the feeding strategies of the birds, says Jim Ludwig, an ecologist with Ecological Restoration Research & Consulting, an independent environmental firm in Nova Scotia, Canada. Black-footed's forage during the day near the surface, and Laysan eat squid that surface at night.
The increase in pollutants is most likely due to current use of these chemicals by unregulated countries combined with the legacy of historic use from by the United States and other developed nations, Finkelstein notes. Because these levels are known to be harmful to animals, "this study has very serious health implications for seabirds, marine mammals, and humans," says Andy Wood, a biologist at the British Antarctic Survey in Cambridge, U.K.
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