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At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
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Pesticide Brew Spells Trouble for Salmon
16 February 2008 (All day)
Salmon in the U.S. Pacific Northwest, and elsewhere, have been in a world of hurt for decades. One of their main enemies is agricultural chemicals, such as chlorpyrifos. The pesticide interferes with salmon brains and harms their ability to feed, according to studies by zoologist Nathaniel Scholz of the National Oceanic and Atmospheric Administration in Seattle, Washington. Now Scholz's research is showing that mixtures of pesticides are even worse for salmon and can be surprisingly lethal.
Chlorpyrifos and other so-called organophosphate pesticides kill cells by inhibiting acetylcholinesterase, an enzyme that helps neurons communicate. These pesticides are sprayed on crops and are widespread in streams in the Northwest; half of the waters sampled by the U.S. Geological Survey contain six or more pesticides. In their previous work with salmon, Scholz and his colleagues had only looked at the effects of one pesticide. To get a more realistic idea of exposure, they designed lab experiments to test effects of mixtures of chlorpyrifos and four other pesticides, exposing juvenile salmon to two compounds at a time.
At the highest concentrations, which exceeded natural conditions, all the various combinations of pesticides inhibited the activity of acetylcholinesterase by at least 50%--a level which impacts behavior. The two lower concentrations were more realistic, and at that level, a quarter of the combinations put a crimp on acetylcholinesterase. What's particularly important, Scholz says, is that the total impact was greater than the sum of the two pesticides, demonstrating a synergistic effect.
The biggest surprise was the strength of the synergistic punch from the pesticides diazinon and malathion, which killed all the salmon exposed to them. Even at the lowest concentration, fish were extremely sick, Scholz says. "It was eye-opening," Scholz says. "We're seeing relatively dramatic departures" from what happens with each pesticide by itself.
Scholz says the findings, which are in review for publication, mean that the U.S. Environmental Protection Agency may be underestimating the hazard pesticides pose to salmon. Given the hundreds of millions of dollars being spent to help salmon populations recover, it's crucial to have a good handle on the biggest threats, he adds.
"It's quite an advance that they were able to examine this in such detail," says toxicologist Derek Muir of Environment Canada's Aquatic Ecosystem Protection Research Branch in Burlington, Ontario. "It's quite significant work," he says. Because there is a good deal of information about where pesticides are sprayed, Muir continues, it may be possible to estimate the impact on wild populations. But factoring in all the other chemicals in streams will be difficult, he cautions.