by Arizona State University (ASU)
ASU postdoctoral researcher Sheryl Murdock advises ASU PhD student Alexi Avery before a dive in “Alvin,” a specialized “human occupied vehicle,” or HOV, used by researchers to explore the deep sea. The dive is part of an ocean expedition to study deep-sea hydrothermal vents. Photo courtesy of Kaitlin Noyes
Imagine descending nearly a mile and a half into a watery abyss, watching the sunlight disappear as the world around you turns completely black. Then suddenly, you find yourself surrounded by a shower of brilliant, bioluminescent fireworks.
This is just the beginning of an ocean expedition into the realm of deep-sea hydrothermal vents — alien ecosystems teeming with life we have yet to fully understand. Here, a place where the sunlight never reaches, crabs, rays and fish thrive even under the extreme hydrostatic pressure.
A team of intrepid researchers from Arizona State University embarked on a recent journey to these hidden depths to learn more about nitrogen cycling and the microbial life thriving in these extreme conditions. These microscopic organisms play a vital role in the ocean’s delicate chemistry.
“I think the deep sea is one of the final frontiers of exploration on Earth,” said Carolynn Harris, a postdoctoral researcher in ASU’s School of Earth and Space Exploration. “We know more about the surface of the moon than we know about the bottom of the ocean on our own planet.”
Sheryl Murdock, a postdoctoral research scholar with ASU’s School of Ocean Futures, part of the Julie Ann Wrigley Global Futures Laboratory, led the expedition along with Elizabeth Trembath-Reichert, an associate professor with the School of Earth and Space Exploration. Six ASU students and staff participated, working on everything from taking samples and planning the next day’s dive, to testing equipment and leading the team’s experiments and school outreach.
Murdock and her research team are working to understand exactly what the smallest inhabitants of the ocean are contributing to ocean chemistry. While microbes are tiny, they have a tremendous impact, and Murdock says they’re not something that gets thought about often when it comes to protecting and managing the ocean.
“Nobody’s going to buy the ‘save the microbes’ bumper sticker,” Murdock said. “We need the public to know that the way the chemistry of the ocean stays in balance has loads to do with microbes and how they cycle nitrogen and other chemical elements. And by understanding what microbes contribute, we can learn how that plays into the wider ocean chemistry and, importantly, ocean health.”
One way the researchers learn more is by taking samples of microbes that thrive under deep-sea pressure — gathered from water and sediment samples. But this team is trying something that has never been done before.
“We are working to understand the microbes living in tubeworm communities by sampling the fluids and then bringing the water back onto the ship, running incubations, and looking at how those microbes use different sources of nitrogen,” Murdock said. “What’s novel about this is bringing them to the surface but keeping them under seafloor pressure and running experiments at that high pressure.”
This process is difficult at best. The team must travel far out to sea on a ship called the R/V Atlantis — a U.S. Navy-owned research vessel operated by the Woods Hole Oceanographic Institution. This ship is designed specifically to launch Alvin, a specialized “human occupied vehicle,” or HOV, used by researchers to explore the deep sea.
Once the team reached its final destination in the Pacific northwest — a spreading center between tectonic plates called the Juan de Fuca Ridge — the team performed multiple dives in the submersible, as weather conditions allowed.
Their innovative approach to collecting water, sediment and microbial samples — bringing them to the surface under the same pressure — is expected to bring new insights to our understanding of ocean chemistry, what roles microbes play on the seafloor, and how they contribute to ecosystem health and function.
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