Bizarro Life-Forms Inhabiting Deep-Sea Vents May Be at Risk

Date: August 4, 2017

Source: Scientific America
Author: Shannon Hall

Two years ago, Shana Goffredi raced to the control room of the R/V Western Flyer, a 117-foot-long research ship in the Gulf of California. Television monitors onboard the vessel displayed what looked like an alien world near the ocean bottom, and Goffredi wanted to get a better look. On screen were thousands of tiny orange tube worms and dozens of other animals, some of which were new to science. The bizarre habitat gleamed in the lights of an underwater robotic probe as it explored the environs of a seafloor spring spewing water at superhot temperatures—known as a hydrothermal vent. What struck Goffredi, a marine biologist at Occidental College, along with the 10 other scientists onboard was how different the life-forms at this site, called the Pescadero Basin, looked from those at a neighboring site. Some 75 kilometers away in the same gulf, vents within the Alarcón Rise also hosted masses of tube worms, only they were blood-red in color. Overall, the two sites shared only seven out of 61 animal species identified. “There’s nowhere else in the world where you have this dramatic difference of species at this close of a place,” says Shannon Johnson, an MBARI researcher who was also onboard that day.

Recent research has hinted that neighboring hydrothermal vents might host different arrays of life, but the scene in the Gulf of California, as Goffredi, Johnson and their colleagues described it in the July 26 Proceedings of the Royal Society B (pdf),provides one of the first dramatic examples of this trend. Goffredi’s team thinks the local geology and chemistry of each vent effectively selects for a rare and specialized animal community that may only be able to live at that site.

The search for these hot waters began in 2012 when MBARI scientists sent a missile-shaped underwater drone to map the Pescadero Basin following a discovery of chemical anomalies that suggested the presence of vents. Although the drone was able to find them, it lacked instruments that could image any animal communities. So, in April 2015 MBARI scientists sent down an SUV-size remotely operated vehicle to take footage of the vents and collect samples of the surrounding seawater, mud, rocks and animals. It was during this cruise that Goffredi and Johnson found themselves glued to the incoming images. And they were not alone. “All of us were out of our seats, taking pictures of the screens with our phones,” Johnson says. “We looked like a bunch of tourists!”

Although it was immediately evident to everyone onboard that the animals found at vents within the Pescadero Basin were radically different from those found at the neighboring Alarcón Rise, scientists could not immediately explain why. Riftia, the blood-red tubeworms seen at the Alarcón Rise, are known to travel great distances. Not only have they been spotted in the Gulf of California, they have also been found in the Galápagos Archipelago and near Easter Island. Although that in itself was initially a mystery, scientists now know these animals release tiny larvae that get carried by ocean currents to different vents, where they settle and form a new colony. Still, their exact movements remain unknown. In recent years it was thought that Riftia and other vent organisms might migrate in a stepwise manner, moving from one vent to the immediate neighboring vent and so on. But the new work by Goffredi’s team suggests the larvae will not settle for any old vent. “They’re kind of like Goldilocks,” Johnson says. “They have to find the right environment to be comfortable and thrive.”

In fact, the itinerant next generation might die if it encounters any vent with radically different geology and chemistry from its home vent. Larvae can travel great distances, but they might have to skip neighboring vents should they be, say, too hot or too cold, and venture farther to seek a suitable home. In seas that are well populated with vents that will not be a problem, but in a sparsely populated area it gets trickier—and every vent becomes more critical, says Cindy Van Dover, a deep-sea biologist and director of the Duke University Marine Laboratory, who was not involved in the discovery.

Read more

Posted on Categories ScienceTags