Hydrothermal vents - deep, volcanic cuts in the ocean floor - are among the most extreme environments where life exists. Now robots have explored the deepest vent and found a network of "ocean-bottom jets" that creatures use for swift transportation.
The deepest volcanic vent in the world
A British research team with the National Oceanographic Centre has been probing the Cayman Trough in the Caribbean. Deep in the recesses of this trench, they've found the deepest known volcanic vent - a "black smoker" some 5,000m beneath the surface. Around 800m deeper than any previously recorded vents, the erupting water is hot enough to melt lead.
At that depth, pressure reaches 500 times surface levels, and yet this vent creates copper and iron ore spires that stretch up the equivalent of two-storeys. The team is using two undersea crafts to explore these briny depths, the Autosub6000 and the HyBIS (Hydraulic Benthic Interactive Sampler), and are now in the process of comparing the life found at 3km deep to that found in other deep sea vents. They've also pulled together a multinational team aboard the RRS James Cook, in order to study the physics, chemistry, geology and biology of the deep vents. Their findings are being documented online, on their website.
When an eruption wipes out all life in a vent
How does life spread to these deep vents? Scientists from the Woods Hole Oceanographic Institution were given an unprecedented insight into how these tiny ecosystems develop, thanks to fortuitous timing. The team were studying a vent in the East Pacific Rise, and happened to be on site when the vent erupted in 2006. The event was so cataclysmic that it destroyed almost all the life that lived at the vent, rendering it a barren seascape. "Although the vents survived, the animals did not, and virtually all of the detectable invertebrate communities were paved over," said Lauren S. Mullineaux, a senior scientist in WHOI. "For us, this was an exciting event. In essence it was a natural clearance experiment that allowed us to explore how this elimination of local source populations affected the supply of larvae and re-colonization."
The ocean-bottom transportation network
Current research suggested that nearby vents and ecosystems would be the first to colonize the newly lifeless, but still energy rich, vent. However, one of the first critters on the scene was the larva of Ctenopelta porifera, which seems to have travelled 350km along the sea floor from the nearest population in order to settle the vent. C. porifera is a deep sea gastropod, that would have had to make it hundreds of kilometers in the 30 days it remains a larva.
"The processes of the larval stage-as opposed to those of adult organisms—seem to control colonization," Mullineaux says. "We found that a pioneer colonization event by Ctenopelta radically changed the community structure."
So how did these baby bugs get to thermal vents, across such a deep stretch of water? It's a bit of a mystery right now, but the researchers theorize that it may be due to ocean-bottom jets, which travel as fast as 10cm a second. Even hitching on these ridge-crest jets, it's hard to get the C. porifera across 350km in just 30 days, which means there's either an additional transport mechanism at work, or else the larvae are somehow extending their lifespan by reducing their metabolism. Mullineaux posits that they may be catching a ride on large eddies that are sometimes hundreds of kilometers wide.
Between these two studies, we're gaining a better understanding of what lives in these deep, dark heat vents, and how they got there in the first place.
Top image via AP/NSF NOAA