Submersibles such as Alvin have made studies of the bizarre creatures that live near undersea hydrothermal-vent systems possible. Unfortunately, the subs' intense floodlights have also blinded many deep-dwelling animals.
Oceanographer Peter Herring of Southampton Oceanography Center in England was the first to identify the harmful effects. While on a research cruise two years ago, he noticed something strange about the eyes of the vent shrimp he brought up to the surface in the submersible Nautile. Instead of a healthy pink, the eyes of many were strangely white. To find out why, Herring gave the specimens to zoologists Peter Shelton and Ted Gaten of Leicester University.
"All the shrimp had some sign of breakdown of the retina," says Shelton. "The photoreceptors of some were completely missing." In contrast, the eyes of juvenile shrimp caught by trawling in the waters above the vents--and never subjected to light--were normal.
Researchers don't know what light levels will damage the shrimps' eyes, which the creatures are thought to use to detect faint light produced by chemical reactions at the vents. "In the long term, I suspect that the occasional visit by a submersible will have little effect on the populations, because the site can become recolonized by new shrimp," says Shelton. But researchers studying the behavior of these animals, he adds, certainly have to be aware that they are harming them and are not observing the shrimps' normal interactions.