An active underwater volcano which spews torrents of lava and noxious gas has become a surprising hotspot for sea critters, scientists revealed today.

Studying them may provide answers to how sea life could adapt to the world's increasingly acidic oceans, they said.

Lava erupts onto the seafloor from the NW Rota-1 volcano, creating an acidic plume

The unique volcano near the island of Guam erupts so frequently that it has built a new cone 131ft high and 984ft wide in just three years.

'That's as tall as a 12-story building and as wide as a full city block,' said expedition leader Bill Chadwick, a volcanologist at Oregon State University.

But despite the tumultuous conditions a large number of creatures including shrimp, crab, limpets and barnacles, have thrived at the volcano called NW Rota-1.

'They're specially adapted to their environment and are thriving in harsh chemical conditions that would be toxic to normal marine life,' said Chadwick.

'Life here is actually nourished by the erupting volcano.'

Two unique species of shrimp were discovered at the volcano, which had adapted to the acidic conditions
Sea water is slightly alkaline, but the rise of carbon dioxide in the atmosphere has been mirrored by an increase of CO2 dissolving in the oceans and forming carbonic acid.

Ocean acidification is a serious concern because it can be fatal to some fish eggs and larvae and interferes with the formation of shells.

'Submarine volcanoes are places where we can study how animals have adapted to very acidic conditions,' Chadwick said.

'Volcanic gases make the eruption cloud extremely acidic - worse than stomach acid.'

Verena Tunnicliffe, a biologist from the University of Victoria, said that two species of shrimp had revealed intriguing adaptations to volcano living.

'The 'Loihi' shrimp has adapted to grazing the bacterial filaments with tiny claws like garden shears,' said Tunnicliffe.

'The second shrimp is a new species - they also graze as juveniles, but as they grow to adult stage, their front claws enlarge and they become predators.'

The new species attacks the Loihi shrimp and preys on marine life that wanders too close to the volcanic plumes and dies.

'We saw dying fish, squid, and so on, raining down onto the sea mount, where they were jumped on by the volcano shrimp - a lovely adaptation to exploiting the noxious effects of the volcano,' Tunnicliffe said.

The international science team had previously visited the hydrothermal site in 2004 and 2006, but this was the first time they studies the volcano in detail and close up.

Jason's arm (top right) samples the gas spewing from the volcano NW Rota-1. The dark rocks are lava.
The latest mission took place during April 2009 and the team captured dramatic new images of the volcano's eruptive behavior with the remotely operated vehicle Jason.

'It was amazing how close Jason can get to the eruptive vent because the pressure at a depth of 1,700 feet in the ocean keeps the energy released from the volcano from becoming too explosive,' Chadwick added.

Some of the most intriguing observations came when the volcano slowly pushed lava up and out of the erupting vent.

'As this was happening, the ground in front of us shuddered and quaked, and huge blocks were bulldozed out of the way to make room for new lava emerging from the vent,' Chadwick said.

NW Rota-1 provides a one-of-a-kind natural laboratory for the investigation of undersea volcanic activity and its relation to chemical-based ecosystems at hydrothermal vents, where life on Earth may have originated.

'It is unusual for a volcano to be continuously active, even on land,' Chadwick pointed out.

'This presents us with a fantastic opportunity to learn about processes we've never been able to directly observe before,' he said.

Part of the evidence that the volcano is in a constant state of eruption comes from an underwater microphone - or hydrophone - that was deployed a year ago at NW Rota-1 by OSU geologist Bob Dziak.

The hydrophone 'listened' for the sounds of volcanic activity. Another hydrophone and other instruments will monitor the volcano in the coming year.

The international team included scientists from OSU, the University of Washington, University of Victoria, University of Oregon, NOAA's Pacific Marine Environmental Laboratory, New Zealand and Japan. The research was funded by the National Science Foundation.