Life After Death for Deep Sea Vents


Deep sea hydrothermal vents support life even after the jets of hot, nutrient rich water stop flowing. And while nobody has yet done the time-series work needed to show just how microbial communities change before and after a vent system shuts down – comparing active and inactive chimneys is proving that “life indeed goes on after the death of a vent,” biologist Tim Shank of the Woods Hole Oceanographic Institution told Discovery News. “Microbes are on extinct sulfide deposits that have been inactive for decades,” he explained.

“It seems, on the deep-sea floor, some form of life is everywhere conditions are suitable,” Shank said.

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One of the reasons why determining ecological succession at vents sites is tricky, is because predicting when a site will shut down is difficult. Only recently have geologists successfully predicted the eruption of an underwater volcano. But though eruptions pave the way, or rather pave over the site, for new communities to develop – the vent systems are still active and the communities that follow are usually similar in nature to the ones that had colonized prior to the lava inundations.

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When the vent systems go stone cold, the communities change again. And oceanographers strongly suspect the shift in the microbial ecosystem is a driving factor as to what happens next.

A recent method for sequencing bacteria, called the V6 deep sequencing approach, has now emerged as the “new standard for this kind of work,” Shank said.

Over at the University of Southern California, postdoctoral scholar Jason Sylvan working with microbiologist Katrina Edwards, and Brandy Toner of the University of Minnesota, have once more proven the success of the V6 method. His team, publishing in the journal mBio, compared bacteria between active and inactive sites, as several others have done as well, but using the V6 method they were able to more fully explore the variations in the genetic code and gain a more fined-tuned understanding of the type of bacteria that feed on the iron and sulfur husks of the dead chimneys.

By tagging the V6 region of the 16S rRNA gene of the microbes, they found that many different types of species are taking advantage of the dead vent sites and are likely each carving out their own ecological niche.

Their work supports the observations that Shank is finding with his team’s microbial studies using deployed rock samples of sterilized basalts. “We have seen dramatic shifts in microbial community structure on the order of days. Remarkable. Now, we are trying to figure out how this might influence the colonization of vent fauna,” Shank said explaining that the microbes could potentially have the capability to either inhibit or promote other organisms becoming established.

“It’s certainly fascinating to learn more about the processes by which these submarine vents keep on “giving” by providing a substrate for life well after the vents themselves become inactive,” commented geochemist Julie Bryce of the University of New Hampshire.

(Neither Shank or Bryce were involved in the study by Sylvan and his team.)

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Deep sea hydrothermal vent beneath Antarctica. Scale bar: 1 m for foreground (PLoS, Wikimedia Commons)