Science knows a lot about the flora and fauna living on our planet
We admire their variety, their beauty
Their incredible capacity to adapt, allowing them to survive anywhere
or almost...
But what do we know about the things happening under our feet
in the shallow and deepest layers of the ground
In his "travel to the center of the earth", Verne described caves and wells
Where prehistoric fauna and flora was surviving
A fantasy? Not so sure...
Scientists invited us to join them in this underground maze
where so many surprises await us
They take us into gigantic caves forged with water and time
they show us mineral jewels of breathtaking beauty
they show us species which defy imagination
Entering a cave, the first creature you are likely to meet is a bat
This strange animal lives at the frontier between 2 worlds
ours, and the underground
Bats are troglophile, which means they occasionally live in underground caves
But they couldn't survive solely in this environment
Through their trips between their caves and the outside, they play an unexpected role
They feed the underground world
"This is bat's guano, which we'll find everywhere in this cave"
"They produce it as they fly, but also as they sleep"
"and this organic matter is beneficial to many animal species"
The bat is the first link in a fragile food chain
She feeds on nocturnal insects, which very few species can hunt
Endowed with an unrivaled agility, she catches her preys with her claws
These acrobatic performances are the result of a 50,000 years long adaptation
In order to understand this ability,
Dr Schoekle penetrates the narrow passages used by the bats
To record their activity, the biologist installs several infrared projectors...
They will preserve the dark
"the colony goes 150 meters deeper, we're already 50 meters down"
"When they go out at night they take just a few seconds to escape these narrow corridors"
Flying at more than 20 mph in these narrow and dark places
The bat needs, for that, a great navigation tool
An eco-location system
She constantly produces ultrasound that echo from the surrounding obstacles and return to her
This way, she has a 3 dimensional view of space, and avoids any hurdle
"of course we constantly receive an incredible quantity of echo , especially in such a busy place"
"they can analyze this echo with an impressive speed"
"their neurological connections are 1,000 faster than ours"
Dr Shoeckle films with a high speed camera, more than 2,000 images per second
In order to break down the bat's flying pattern
The rugged relief of the caves has shaped their flying abilities
Their ability to suddenly change their course is impressive
"These are animals who, in their acrobacies and maneuvres..."
"have no equivalent with regular birds."
"That is because bats' fingers go to the end of their wings"
"So they can bend a single finger to correct their trajectory, all this at great speed"
Through her long adaptation, during which her flying and radar abilities have improved,
The bat has become a vital link between the ungerground and overground species
"The bats are at the head of an ecostytem that survives on this organic matter"
"without it, this underground life would disappear"
"whether it is microorganisms or insects"
Let's dive deeper into this fragile ecosystem, located on the fringe of the bats' territory
Here begins the world of Dr Alonzo, a bio-speleologist
With patience and rigor, he studies the tiny fauna that lives in the caves
These species are so small, that a 1m² inventory can take several hours
"The underground isn't just made of minerals..."
"We can find life in almost every cave in the world"
"There is a fauna, so well adapted to darkness, that it won't get out"
"called a troglofauna, whose study is particularly interesting for scientists"
"If we want to understand phenomenons of adaptation"
These Troglophile species have become so adapted to the underground world,
that they could no longer survive on the surface
A full food chain has developed in the dark
Shut in a dark in mineral world, the troglobyte fauna still depends on the outside world to survive
Apart from the bats' guano, other surface waste can enter through the entrance of the cave
Or be carried with the waters
How did these tiny animals colonize the underground world?
"Here he is, hidden behind the rock, a diplopoda
"Some, on the surface, resemble him, just with more colors"
"we call them millepedes, they can curve into balls"
"here's a beautiful one, of a good size"
"many of them have their ancestors on the surface. The most primitive species are outside"
"so it's normal to see similarities in shapes, for instance the millipedes"
"who have the same appearance as the surface millipedes, but with different characteristics due to evolution'
The troglofauna is the evolved cousin of the surface species
Trapped underground during climatic or geological incidents...
This evolution took thousands of years
Surface species have a darker epidermis, protecting them from sunlight
This protection is useless for those living underground
The troglofauna has lost its original colors
Another important difference, legs and antennas have grown longer
Surface species have eyes, so they can move around avoiding obstacles
The troglofauna has no eyes. They wouldn't use it in the dark
Their eyes can be replaced by tactile organs
For some species, these are bigger than the rest of their bodies
The troglofauna often feel around as it walks
The underground water bodies are also colonized by troglofauna
Especially by crustaceans, some of which look strangely like shrimps
"There are so many underground species, each one has its own story"
"Some crustacean here have a marine origin"
"hundred thousands years ago the sea covered this area, and then retracted, leaving some underground lakes
"species were trapped, and little by little rain water came to replace the salt in the lakes"
"the species adapted to soft water"
"today you get these cave crustacean living in soft water"
In the underground lakes, food is much rarer than on surface rivers or ponds
Finding it requires a lot of efforts, and the weak doesn't survive times of scarcity
The most voracious, like the niphargus, feed on their corpses
The deeper the water gets, the rarest the food becomes
The scarcity of food didn't prevent Europe's biggest cave predator to settle here.
Almost 30 million years ago.
His lifestyle is astonishing
He lives hidden in tiny cracks
His territory is so hard to access that adult specimen could never be observed in the wild
This wonderful animal is the olm, nicknamed the white salamander, or cave salamander
To break this enigma, French scientist have dug an underground laboratory in Moulis
At the bottom of the Pyrenneans
Dr Guillaume, a biologist with CNRS...
wonders about the life expectancy of such a small animal
"The olm is an amphibian, close to the salamander"
"The only cave vertebrate in Europe"
"he has developed characteristics of cave species, like the lack of color"
"the one I am holding here is not yet an adult...
"he is 14. Their sexual maturity comes at around 15.
"they can live between 80 to 100 years"
The olms' development is particular
At the stage of larva, its resemblence with his salamander cousin is great
Both larvas breathe through external gills
But when surface salamander become adults, they lose their gills
And develop lungs
The olm will never have lungs. His whole life, he breathes through his gills
He will remain in a quasi larva stage, even when he acquires a sexual maturity and starts reproducing
At birth, he has eyes, which degenerate with time
"The olm is very efficient in his environment using his smell"
"he produces pheromones, scented molecules
"And he can follow their trace, like ants would"
"it's an animal that moves very little, spending most of his time in cracks"
"in such an environment, with a lack of food"
"he's basically saving his strengths, and besides he has no predator, and no need to flee"
Hidden in a crack, or under a rock, the olm waits for food to come his way
In such a scarce environment, he relies on chance, that may bring waste from the surface
"For the experiment, we starved him for a few months"
"and we can see that he's not losing weight, or hardly"
"so he has great surviving capacities
"In history, some researchers have starved them for 48 months"
"without ever causing a death"
To undergo 4 years without food, for an animal that can survive 80 years...
It is a mystery that fascinates many scientists
"When you observe the olm's behavior, you can see he stays idle for several days"
"but he still maintain a rhythm with his metabolism"
"It's the same for men, during sleep, where we still produce hormones and prepare for wake up"
The experimental staton in Moulis recreates the olm's environment
The water temperature is stable, and darkness is constant
The olms' movements are constantlry recorded by infrared cameras
Their oxygen consuption is measured to calculate their metabolism
Many months of data, in an automatic computer...
are necessary to give results, always very slow in coming.
In spite of its lack of activity, and the lack of day/night alternance...
Dr Guillaume observed 10 to 12 hours metabolic cycles in the olm
Probably inherited from his ancestors
"the advantage of maintaining this rhythm in a constant environment"
"is for the olm to be able to measure time, and have a strategy to manage energy"
"His inactivity is one factor that can explain his long life, from 80 to 100 years
"by staying inactive, not spending energy..."
"he doesn't produce toxic subproducts that can cause a senescence, meaning an aging of the cells"
The extremely slow life of the olm is the condition for survival in such an austere and poor environment
This predator is at the mercy of the troglofauna
whose larvas and wastes he eats, as they arrive through underground streams
He also depends on the organic matter carried by surface waters
Vital for the underground life's survival, these waters were at the origin of the formation of the caves
Rain and ice waters are acid, and full of minerals
They slip into the soil's cracks, and start a long journey underground
Caves can only appear in soils that can welcome these waters
Among these, limestone soils
They are soft, and vulnerable to acidity
The mechanic strength of the water attacks the limestone, and its acidity dissolves it
Each drop falling from the ceiling, each stream running through the rocks....
leaves a tiny mineral deposit, which adds to previous ones
Thus, drop by drop, the underground world becomes mineral
This process takes place over thousands of years
Thus were born fantastic underground cathedrals
Their barocco architecture is a result of rock and water's whims
Thus appeared the pillars, the drapes, the coloumns' forests of the richest caves
In a universe that knows only wter and rock, the fauna meets its limits
Here starts the reigns of another lifestyle
A few years ago, after moving in a narrow underground corridor...
a team of speleologists led by Dr Randin, made a surprising discovery
Feeling that they had just discovered an unknown mineral compound....
The team prohibited any entrance to the cave to prevent degradations
and called dr Monteux, a former speleologist, now professor in Sweden
"What we call concretion is simply the limescale in the water that evaporates and forms these cristals"
"and as it drips down forms these stalagmites attached to the top"
"or can make drape forms"
"but it can take other forms, when it follows the air flow, we call it eccentrics"
As understood by their name, eccentrics take chaotic shapes
While classic concretions are formed following gravity
Their lack of orientation is explained by the fact...
that in some areas of the cave, the forces of gravity, capillarity, and cristallisation are equivalent
Thus, they neutralize each other, and the concretions' forms become random
Dr Randin's teams' concretions are eccentrics...
but they show troubling characteristics
The branches have a bigger than usual diameter
And in some areas, they defy gravity
Strangly, they look like plants, but plants that would be mineral
The scientists are faced with an enigma
"these structures that look like bridges..."
"we see it going up, touching the roof, then into another direction..."
"and back to the roof, and so on..."
"these are very unusual structures but we can find them in several areas"
"it's hard to believe that these are just random"
"so we started to think the answer was biological"
To solve the mystery, dr Monteux takes a sample...
and submit it to a scanner
"Here are the scan results, with only two colors, orange for the biological parts...
"yellow for the minerals"
"we can see the 2 are connected"
"there's organic on the surface and on the inside"
"and even inside the mineral itself"
- "we see it's completely mixed"
- "so not just a random presence"
"not just a random bacteria, but something that is at the origin of the structure"
"either at the origin or involved in the development, we can't say, but they're not random"
According to the scan, it is neither gravity, nor the water flow, nor the air flow that created these concretions
But millions of bacteria
They change the rock into calcite, and with time, come to create these tree like minerals
One question remains...
Why do branches grow upward?
"just above these concretions is a darker layer with heavy metals like zinc, aluminium or copper..."
"And a lot of sulfur"
"to see this visible layer here, and these branches growing towards it..."
"we thought that the bacteria try to grow towards this layer to feed on this sulfur"
"as bacteria can use sulfur to develop"
Another structural oddity intrigues the scientist
In several places, concretions connect to one another
"we know that on a small scale bacteria can communicate"
"it is called quorum sensing"
"and we think these bacteria, which have orientation"
"in these very calm conditions"
"would be able to sense molecules on a greater distance, and thus move towards one another"
The DNA analysis of this concretions confirms the presence of bacteria
It also shows a great diversity
30% belong to unknown species
"until recently we didn't focus on what lived inside rocks"
"until we found rocks were not dead and empty"
"and so this frontier that is the cave, between the organic that we know..."
"and the mineral, is like an entry gate to this underground life which is gigantic"
Study of these bacteria is still just starting
But they hold many promises for the understanding of underground life
The bacteria, able to feed on sulfur and heavy metals...
Are they the only organism able to colonize the underground world?
The lowest point ever reached by speleologists is 2,000 meters below ground
Only the mines, especially South African ones, go even deeper
And give access to extreme depths
In the beatrix mine, the Dr Borgoni
tries to study the presence of mutlicellular organisms
at 3,300 meters below ground
His project was met with disbelief
As it seemed extravagant
"Underground life is much more complicated than we thought"
"there are some extremophile bacteria we can't see"
"strange things are going on there, and the idea of finding complex multicellular organisms
"used to be regarded as crazy"
Life cannot develop without water
So the scientist is looking for life in the infiltration waters
"So we have a drilling in the crack, and the pressure is extreme as you can see"
"We attached this container here, which should retain anything bigger than a bacteria"
"There's a filter, and the water in it is exactly the same as the one in the rock"
"it's why this little wheel prevents any foreign body from going back"
"We leave it for days, months, or years"
"and when we return, we take it to the lab, open it in sterile conditions...
"And we look at what's inside"
The first sample from the filter contained nematode worms
Little worms with a ringless body
"A nematode is a round worm, they're everywhere, from the deepest sea to the highest mountain"
"they range from a few microns to several meters"
"we find them everywhere because they adapt to any environment"
"they have remained very archaic. They are among the oldest multicellular species on this planet"
"they have biochemical characteristics found in plants"
"and genetic characteristics found in bacteria"
"which shows that they are quite old in evolution"
To understand what these worms feed on at such depths...
Dr Borgonie goes to an old diamond mine, stardiamond.
Opened in the 1900's
For him, no doubt. The nematodes get their food from the rock itself
In the mine he finds a crucial clue.
Bacterial colonies that accumulate in a water stream in the shape of a white filament
With an endoscope, he goes back up the crack, to learn more about these bacteria
"We have a drilling here about 30cm deep in the rock...
ending in a small cave where the bacteria are abundant"
"it's the first time we observe that. We took samples, and found nematodes"
"so we know that nematodes develop inside the bacterial biofilm"
"and we found that this biofilm was very large, larger than we had imagined"
Apparently, nematodes feed on bacteria
And it seems every crack in the rock, even the tiniest, is its own ecosystem
This changes the idea we had of the underground world
"if you think of the underground, ost people think that the pressure prevents any space from existing"
"everything is so compressed, there is no crack, but it's the opposite"
"in fact you don't need much space for life"
"think about your thumb, it's big enough to contain nematodes, bacteria, flat worms, or athropodes..."
"so a crack the size of your thumb may not be as big as an African plain...
"But it's enough for life to be abundant"
Can the nematodes really colonize any available space?
On a hunch, Dr Borgonie returns to the Beatrix mine
He takes a stalagmite in formation to analyze it further
"when you look at the stalagmite through a scan, you see it's not a solid crystal mass, but it's in fact hollow"
"you can clearly see many cracks, in which nematodes could live"
"an electronic microscope can open up the stalagmite"
"in pink is the outside layer, hard, solid"
"in brown is the bacterial biofilm"
"And in blue are the nematodes living inside"
"what people don't yet understand..."
"is that if you take a scale"
"and you put underground life versus surface life"
"the scale will tip on underground life. There's more life underground than on the surface"
"and it's really amazing come to think of it"
Thus we know that underground multicellular organisms feed on bacteria
But this answer asks more questions
What do bacteria feed on, how do they colonize the underground?
Part of the answer can be found in Iceland
Volcano activity is intense here, and geothermal energy has long been exploited
Drillings capture the warmth of the volcanoes
And bring it back up to activate the electric plants
Volcanic gas contain a lot of carbon
That is to say, CO2
To prevent it from polluting the atmosphere, the scientists inject it back underground
They think that with the underground pressure, this CO will change into carbonate
Which is a mineral, and will become stable
For Dr Menez, and his team, the Iceland sites are an ideal place to underground bacteria
"In Iceland we have great manipulations, ranging through kilometers"
"with huge quantities of carbon being injected into the ground, so we really can...
"in real time, follow these ecosystems' evolution
"and see the way they react to the carbon injections..."
To know how Iceland's underground is reacting to these CO2 injections,
One needs to drill into the rock that makes the outer layer of the ground.
Will we find a great number of bacteria in the rock samples that are brought back to the surface?
"what determines the limit depth to which we can find life...
"is temperature, there's no life after 120°C, according to what we know"
"and depending on the region, 120°C is about 10 kilometers deep"
Dr Menez is not trying to reach this limit.
She's studying an area between 400 to 500 meters deep
Where the CO2 was injected..
The drilling samples are a unique occasion to access this unknown microbial life.
Under the underground pressure, bacterias have to colonize any cavity to settle and develop
At first glance, the team spots a green color that spikes their interest.
"This green and orange biofilm is everywhere, sometimes with this white crystals of carbonate..."
"and whatever the rock's porosity, even in denser areas..."
"this biofilm is still there feeling every pore..."
"every crack... And we've seen it over 30 meter since we reached 410 meters"
"it's surprising because this CO2 did not convert into minerals but instead..."
"but instead fed microorganisms that invaded every pore and developed"
The bacteria appear very abundant, at a depth where food is very scarse
This impressive abundance could be the result of CO2 injection into the ground
To make sure of it, Dr Menez and her team fraction some samples, and chemically prepare them for study
In order to know where these bacteria get their food from...
the scientists had to create a special microscope
which distinguishes microorganisms from minerals
and thus, can analyze their interaction
"did you find something in the sample we brought the other day?"
"I colored them to see microoganisms better...."
"all these are small cells that associate with one another"
"creating bacterial branches, in green here"
"little by little the branch is colonized by minerals too"
"Here you can see the minerals are in pink, and the bacteria in green"
"it will be interesting to find what they feed on"
"so they are basically changing the rock by creating these new structures"
"there are so many chemical reactions taking place underground"
"we need to know if they feed on these reactions"
"they're actually feeding on deep fluids, so it's independent from surface activity"
The microscope proved it, the bacteria and the minerals are interacting
But this doesn't explain where these bacteria find their food
In such a compact environment, so far from the surface
Unless this organic matter might be produced by the rock itself
"these rocks aren't supposed to be on the surface, so when we put them in contact with water..."
"they become unstable and turn this water into hydrogen"
"and this hydrogen is the key between non organic and organic worlds"
This contact between water and rocks provokes a chemical reaction that creates hydrogen
This gas associates with carbon that is naturally or artificially present in the rock
This combination generates complex organic molecules among which...
methane.
And methane is a privileged food for bacteria.
Thus, they can find an abundant food inside the rock layer
We have reached the frontier between the mineral and the organic
This discovery is an important advance in the understanding of life.
Among the molecules produced, some amino acids...
They are the most fundamental elements of life.
Our bodies, as any other species on earth, is made up of amino acids and water
The underground world is not hell, where the dead would rest...
As ancient Greeks would believe.
Today, we are finding that the underground played an active role in the development of life
The exploration of the underground as Jules Verne imagined it, has just started.
It probably holds as many surprises as the exploration of the universe
