Methane ecosystem found in caves of the Yucatan Peninsula 

alibhai/ November 28, 2017/ New Gadgets/ 0 comments

  • The methane-fueled ecosystem feeds bacteria in the underground caves
  • In these caves, methane and bacteria form a vital part of the overall ecosystem 
  • It explains how cave adapted animals survive without visible evidence of food
  •  The research could help researchers understand how sea level rise and seaside development could impact these ecosystems

Researchers have discovered a methane-fueled ecosystem that feeds bacteria in the underground rivers and flooded caves of Mexico‘s Yucatan Peninsula. 

In these caves, which Mayan lore describes as a fantastical underworld, methane and the bacteria that feed off it form a vital part of an ecosystem that is similar to what’s been found in deep ocean cold seeps and some lakes. 

This explains how cave adapted animals are able to survive without any visible evidence of food, and more broadly, the research could help researchers understand how sea level rise and seaside development could impact these ecosystems. 

Cave passage and diver within a section of the Ox Bel Ha cave system where the current study was conducted. The guideline seen alongside the diver that provides a continuous route to the surface is one of many safety standard the divers follow

Cave passage and diver within a section of the Ox Bel Ha cave system where the current study was conducted. The guideline seen alongside the diver that provides a continuous route to the surface is one of many safety standard the divers follow

The researchers, who are trained in cave diving in addition to their other expertise, had to use techniques that had previously been used by deep-sea subs to be able to study the environment.

The study, conducted by researchers at Texas A&M University at Galveston, the US Geological Survey and a team of collaborators from Mexico, The Netherlands, Switzerland and other US institutions, claims to be the most detailed ecological study ever for a coastal cave ecosystem that is always underwater. 

‘The opportunity to work with an international team of experts has been a remarkable experience for me,’ said David Brankovits, who is the study’s lead author and conducted the research during his Ph.D. studies at TAMUG. 

HOW THEY DID THE STUDY 

Researchers have discovered a methane-fueled ecosystem that feeds bacteria in the underground rivers and flooded caves of Mexico’s Yucatan Peninsula. 

In these caves, which Mayan lore describes as a fantastical underworld, methane and the bacteria that feed off it form a vital part of an ecosystem that is similar to what’s been found in deep ocean cold seeps and some lakes. 

Between 2013 and 2016, five field campaign were conducted to investigate cave networks through Cenor bang, the primary study site within the Ox Bel Ha Cave System and secondary locations.

The researchers collected water samples as well as shrimp samples in the caves.  

(a) Entrance pool of Cenote Bang (b) Subsurface vantage of Cenote bang entrance pool, the primary locations where particulate organic detritus enters the system without being filtered

(a) Entrance pool of Cenote Bang (b) Subsurface vantage of Cenote bang entrance pool, the primary locations where particulate organic detritus enters the system without being filtered

The researchers, who are trained in cave diving in addition to their other expertise, had to use techniques that had previously been used by deep-sea submergence vehicles to be able to study the environment.

The freshwater portion of the caves and the sinkholes, which are used to access the caves and are referred to locally as cenotes, are important sources of freshwater for communities throughout the Yucatan. 

After entering the cave, the divers used a guideline to provide a continuous route to the surface is one of many safety standard the divers follow.

‘Finding that methane and other forms of mostly invisible dissolved organic matter are the foundation of the food web in these caves explains why cave-adapted animals are able to thrive in the water column in a habitat without visible evidence of food.’ 

The study was conducted in the Ox Bel Ha cave network in northeastern Yucatan, which is described as a subterranean estuary because the flooded cave passages contain distinct water layers consisting of freshwater fed by rainfall and salt water from the coastal ocean. 

This subterranean estuary complex covers an area about the size of Galveston Bay, the seventh largest surface estuary in the US. 

(e) Typhlatya mitchelli and (f) Typhlatya pearsei, the two species of stygobitic atyid shrimp present at the primary research site

(e) Typhlatya mitchelli and (f) Typhlatya pearsei, the two species of stygobitic atyid shrimp present at the primary research site

The freshwater portion of the caves and the sinkholes, which are used to access the caves and are referred to locally as cenotes, are important sources of freshwater for communities throughout the Yucatan. 

Methane in the caves forms naturally beneath the jungle floor and migrates downward, deep into the water and caves.

Normally, all of the methane formed in soil migrates upwards, towards the atmosphere. 

This sets the stage for the bacteria and other microbes that form the basis of the cave ecosystem. 

The microbes eat both the methane in the water and other dissolved organic material that the freshwater brings with it from the surface. 

Caves within a karst subterranean estuary are filled with separated fresh (green), brackish (gray) and saline (blue) waters. Within the subterranean estuary, methane (CH4) and other forms of dissolved organic carbon (DOC) created during the decomposition of soil from the overlying tropical forest sustain a complex cave-adapted ecosystem

Caves within a karst subterranean estuary are filled with separated fresh (green), brackish (gray) and saline (blue) waters. Within the subterranean estuary, methane (CH4) and other forms of dissolved organic carbon (DOC) created during the decomposition of soil from the overlying tropical forest sustain a complex cave-adapted ecosystem

These microbes then fuel a food web that is dominated by crustaceans, including a cave-adapted shrimp species that obtains about 21 per cent of its nutrition from methane. 

‘The processes we are investigating in these stratified groundwater systems are analogous to what is happening in the global ocean, especially in oxygen minimum zones where deoxygenation is a growing concern,’ says John Pohlman, a coauthor of the study and a USGS biogeochemist whose work from the early 90s motivated the research. 

‘Although accessing these systems requires specialized training and strict adherence to cave diving safety protocols, relative to the complexity of an oceanographic expedition, the field programs we organize are simple and economical.’ 

One surprising finding was how important the dissolved organic material like methane was to the caves’ food web. 

Researchers have discovered a methane-fueled ecosystem that feeds bacteria in the underground rivers and flooded caves of Mexico's Yucatan Peninsula. The study was conducted in the Ox Bel Ha cave network in northeastern Yucatan

Researchers have discovered a methane-fueled ecosystem that feeds bacteria in the underground rivers and flooded caves of Mexico’s Yucatan Peninsula. The study was conducted in the Ox Bel Ha cave network in northeastern Yucatan

Previous studies had assumed that the majority of organic material that feeds the microbes of caves came from vegetation and other detritus (debri) in tropical forests that washed into the caves from the cenotes. 

Deep within the caves, however, the researchers found very little of that surface debri, so the microbes depend on methane and the other dissolved organics percolating downward through the ceiling of the caves. 

‘Providing a model for the basic function of this globally-distributed ecosystem is an important contribution to coastal groundwater ecology and establishes a baseline for evaluating how sea level rise, seaside touristic development and other stressors will impact the viability of these lightless, food-poor systems,’  says Tom Iliffe, a professor in the Marine Biology Department at TAMUG who has been studying the biodiversity, evolution and conservation of marine cave animals for nearly 40 years. 

These are Project Field Team Members (left to right) David Brankovits (TAMUG), Jake Emmert (Moody Gardens), John Pohlman (USGS), and Francisco Bautista De La Cruz (Speleotech)

These are Project Field Team Members (left to right) David Brankovits (TAMUG), Jake Emmert (Moody Gardens), John Pohlman (USGS), and Francisco Bautista De La Cruz (Speleotech)

 

 

 






Courtesy: Daily Mail Online

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