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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...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Where Fish Fear to Tread
11 February 2004 (All day)
The ocean off southwestern Africa supports one of the most plentiful populations of plankton in the world, but for some reason big fish avoid the rich grazing. Now, a team of researchers proposes an explanation: The sea floor appears booby-trapped with poisonous gases.
Anywhere that ocean currents bring nutrients up to the surface, plankton thrive and fish have a field day eating the plankton. But that's not true of the Benguela current, off the coast of Namibia. Fish there are up to 20 times scarcer than in similar regions off Peru. As a result, many plankton fall uneaten to the sea floor. Bacteria decompose them, stripping oxygen out of the water and forming pockets of methane and hydrogen sulfide gas beneath the sediment.
Periodically, these pockets erupt. The air stinks of rotten eggs, sea birds feast on a smorgasbord of dead fish, and oxygen-poor waters send lobsters scurrying onto beaches. Until recently, the explosions were thought be just a local problem. But satellites tell a different story. Images depict huge tracts of the milky, turquoise water, stretching over patches the size of New Jersey and lasting for days. Now a team of oceanographers and fisheries scientists led by Scarla Weeks at the University of Cape Town in South Africa has paired these satellite images with on-the-ground observations of 16 recent eruptions in the Benguela current to look for common triggers and assess the impact on the ecosystem.
Shifts in the weather could be responsible, they report in the February issue of Deep Sea Research. The timing, as well as the size and shape of the eruptions, suggest that a slight lessening of pressure on the sea floor--caused by low-pressure weather systems, warmer water, or stronger upwelling currents--may prompt a few bubbles to escape a large gas pocket. The bubbles would lessen the pressure on the sea floor still more, triggering a bigger eruption, the team speculates. They also suggest that the frequency and extent of the troublesome gas make the region deadly enough to encourage the fish to eat elsewhere.
The fish kills in the region are indeed large, says oceanographer Peter Brewer of the Monterey Bay Aquarium Research Institute in Moss Landing, California. And the big picture of sulfide and other gases creating the patches rings true, although he doesn't believe that the bubble mechanism accurately captures the behavior of gases on the sea floor.