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Marine biologists have discovered large schools of fish that live in the dark depths of the Gulf of California, where there is virtually no oxygen for these species. Using an underwater robot, the scientists observed that these fish thrived in low oxygen conditions that would be fatal for most other fish. This discovery could help scientists understand how other marine animals could cope with the ongoing changes in ocean chemistry.
The researchers described their discovery in a recent article in the journal Ecology. The lead author of the article, Natalya Gallo, is a graduate student at the Scripps Institute of Oceanography. He worked closely with other Scripps researchers in the document, as well as with MBARI biologist Jim Barry, who led the research cruise.
In 2015, Barry, Gallo and eight other researchers conducted a series of dives in several ocean basins in the Gulf of California using the Doc Ricketts, the remote operation vehicle (ROV) of the MBARI (Monterey Bay Aquarium Research Institute), a submarine robot last generation. Gallo was particularly interested in these areas because her doctoral thesis focuses on animals that live in environments with very little oxygen. The deep waters of the Gulf of California have some of the most extreme low oxygen habitats in the world.
“I could hardly believe what I was seeing,” Gallo wrote on the MBARI cruise blog after an ROV dive on the Cerralvo channel. “We observed eels, grenadiers and lollipop sharks swimming actively in areas where the oxygen concentration was less than one percent of typical surface oxygen concentrations We were in a sub-toxic habitat, which should exclude fish, but instead, there were hundreds of fish. “I immediately knew that this was something special that challenged our current understanding of the limits of tolerance to hypoxia [low oxygen level].” In fact, the instruments in the ROV showed that these fish lived in an environment where oxygen concentrations were one tenth to one quarter as low as those tolerated by other fish with low oxygen levels.
In fact, two species of fish (eels and lollipop sharks) seemed to prefer these areas of low oxygen in areas where oxygen concentrations were higher. “Many other types of fish are considered to be tolerant of low oxygen conditions,” Barry said in a statement. “But the fish in these parts of the Gulf are like the winners among a group of elite Olympic athletes.” One of the objectives of Barry’s cruise was to use the large natural variations of oxygen and temperature found in the Gulf to study how communities of seabed animals could change in response to warmer and reduced oxygen conditions that have been predicted by some. climate models.
“The researchers described their discovery in a recent article in the journal Ecology. The lead author of the article, Natalya Gallo, is a graduate student at the Scripps Institute of Oceanography.”
Researchers still do not know exactly how these fish can survive, and even thrive, in such harsh conditions. Both eels and feline sharks have large heads with vibrant red gills, which can be particularly good at absorbing oxygen from the surrounding water. The fish are also small, less than 30 centimeters long, with flaccid bodies and thin, underdeveloped bones, all traits that can help them conserve energy.
Why fish congregate in these particular areas is another mystery. Barry speculates that they may be finding food or avoiding predators. In some areas with little oxygen, the researchers saw snails, starfish and corrals on the seafloor. But in areas with less oxygen, the muddy muddy seabed looked like a sterile lunar landscape, suggesting that even small invertebrates had difficulty surviving. “We hope to return to the Gulf soon to try to address some of these questions,” Barry said.