"Vents and seeps support chemoautotrophs [organisms such as bacteria that get their nourishment from inorganic compounds]," Mullineaux said. "So their faunas are not dependent on photosynthetic production from above, which can be very sparse by the time it gets to the deep sea."
The bacteria that live off the fluids and gases spewing and oozing at vents and seeps support critters that have a mutually beneficial relationship with bacteria, according to Drazen.
The relationship works because the bacteria actually take refuge inside the tube worms, clams, and mussels and convert the chemicals that come from the vents and seeps into food that the larger critters consume.
A third type of biological hot spot is found on underwater mountains known as seamounts. The seamounts are swept by currents, which bring a continuous supply of food to animals that can filter it from the water, such as sponges, anemones, and deep-sea corals.
"Photographs of the tops of seamounts look more similar to a coral reef than to the rest of the deep sea," Drazen said.
As the world's scientists have gained the technology to explore the deep-sea biological hot spots, so to have fishing fleets gained the technology to fish them. The orange roughy in particular has become a delicacy in the U.S.
According to the World Wildlife Fund, the U.S. imports an estimated 19 million pounds (8.6 million kilograms) of the fish each year, accounting for nearly 90 percent of the documented worldwide catch, 60 percent of which comes from the deep seas around New Zealand.
Orange roughy grow 12 to 16 inches (30 to 40 centimeters) long, weigh upward of 4.4 pounds (2 kilograms), and can live as long as 125 years. They gather on seamounts to spawn, where deep-sea trawlers drag their nets, harvesting several tons of fish per hour.
"As various fishing practices go, bottom trawling is a relatively destructive one," said Kim Davis, deputy director for the World Wildlife Fund's marine conservation program in Washington, D.C. "It is not selective and it excavates everything in its path."
The practice has decimated orange roughy populations and done untold damage to the fragile seamount ecosystems. According to Davis, scientific studies suggest that orange roughy will be commercially extinct within the next two decades.
To protect the fish and their habitat, the World Wildlife Fund is recommending that seamounts be protected as marine reserves. "Certainly at least until we figure out what is down there and what we will lose," Davis said.
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