San Diego Biologist Finds Fish Living In Extremely Low Oxygen Content Waters

Tuesday, December 11, 2018

Credit: Scripps Institution of Oceanography

Above: Catshark and cusk eel on the bottom of the ocean in the Gulf of California in this undated photo.

A San Diego oceanographer has discovered two species of fish that are thriving despite living in ocean waters almost devoid of oxygen.

Scripps Institution of Oceanography postdoctoral researcher Natalya Gallo was told she would not find any fish in the low oxygen parts of the Gulf of California.

The ocean bottom there is about 1,000 meters deep and has less than one percent oxygen content.

It turns out, the marine biologist found lots of two kinds of fish, a catshark and a cusk eel. The two species thrived there. There is so little oxygen in those deep waters that the ocean there probably shouldn’t support life.

“Some of these species that have evolved over millions of years of time to live under these conditions that are really metabolically challenging for other animals. They may actually be animals that can increase their habitat in the future under climate change,” Gallo said.

These two fish species could be winners if the planet’s climate continues to warm because it is more difficult for oxygen to dissolve in warmer waters.

She found the small sharks and eels thrive in salt water with less than one percent oxygen. By comparison, Gallo says humans typically breathe air that has 21 percent oxygen content.

“Even if you are in a place where oxygen has dropped to 15 to 19 percent we already start feeling different impacts of hypoxia on our physiology. And then if we’re in an environment where the oxygen drops to 8 to 10 percent. Then we're getting actual mental failure and if oxygen drops any lower than that the consequences are fatal,” Gallo said.

Low oxygen zones in the world’s oceans may expand as the climate warms and that could help increase the range of these two highly specialized species.

However, she also noted that warmer oceans could lead to the creation of spots with no oxygen where even these fish couldn’t survive.

Gallo’s findings are published in the current edition of the on-line journal Ecology.