UAF Scientists help Discover Unique Ecosystem of Cave Shrimp

Juneau, AK (KINY) - Researchers discovered cave shrimp that are surviving by eating bacteria that lives on methane trickling into underwater caves in Mexico's Yucatan Peninsula.

Field scientists dove into the depths of the Ox Bel Ha cave network of the northeastern Yucatan, by plunging into sink holes. There they took shrimp and other samples, which were then studied by a team of scientists led by University of Alaska Fairbanks' Mary Beth Leigh.

Leigh described the process of those field expeditions.

“It involves hiking through the forest with scuba gear and then dropping into a sinkhole. Then, they can access miles and miles of subterranean limestone flooded caves. They are really an interesting network of caves, because the seawater from the nearby ocean actually floods the bottom portion of the case and then on top of that of the layer of fresh water that comes in from above through rainfall that percolates down through the tropical forest.”

“It's really cool to see visually when a diver swims through it, where the water mixes. If it's stirred up it has a different refractive index that creates this cloudy zone where the fresh water meets the salt water.”

Leigh and her team discovered just how these shrimp were surviving in that unique ecosystem, by eating bacteria, bacteria that feeds on methane that comes from the forest above. She explained that food web. . .

“Of course, shrimp can't eat dissolved organic compounds. What happens is that microbes in the soil will start to biodegrade those organic molecules and turn it into methane. There's a certain amount of methane that will be dissolved in water and that dissolved methane is what enters the cave.”

“Then other bacteria will eat that methane and grow on it and then the shrimp will eat those bacteria. So it was an interesting case what we called an upside down food web in which nothing comes down from above and fuels this whole food web in the cave.”

Leigh then shared what her team's role in the research was.

“The cave divers collected the samples and then they sent them to us here in Fairbanks and I was the head of the microbiology team, which was housed here at UAF. What we did was to take the samples that they collected which were in some cases shrimp, shrimp guts, and also water samples. Then we extracted the DNA out of those samples and we analyzed the DNA in order to identify all of microorganisms that were present.”

We asked what applications this research into methane eating microbes could have for the world at large.

“Certainly microbes that produce and consume methane are important, potentially in a biotechnological sense, because we can use methane-producing organisms (we call them methanogens) to generate methane that could be used as a fuel during something like composting or even methane capture from landfills. Microbes that eat methane are beneficial from another standpoint and that's for mitigating the release of methane to the atmosphere.”

“Methane is very potent greenhouse gas it’s about 25 times stronger than CO2 at trapping solar radiation. It causes the greenhouse effect to occur at a much more intense rate than CO2 does and so there's interest in trying to reduce the amount of methane that gets released into the atmosphere. Similarly from landfills or what our biggest issue right now is things like thawing permafrost that are releasing dead organic matter that microbes convert into methane so we’re relying heavily on microbes that eat methane to try to keep that all from going into the atmosphere.”

This upside down methane system shows that there is still much to learn about species living beneath the surface of the ocean.

The research was conducted during field expeditions that were funded by the US Geological Survey, Texas A&M at Galveston, and the National Autonomous University of Mexico. The project started about three years ago, sparked by a previous collaboration.


Image credits

featured - diver (Bil Phillips, cave explorer) in Ox Bel Ha Cave System in the Yucatan Peninsula, photo by HP Hartmann

#1 summary of our findings from the Ox Bel Ha Cave System, by David Brankovits

#2 diver entering a cenote in the Yucatan Peninsula, photo by Sergio Benitez

#3 diver collecting cave-adapted animal for the study in the Yucatan, photo by Balazs Lerner

#4 the team in the Yucatan Peninsula, photo by John Pohlman


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