Subtitles section Play video Print subtitles This is an underwater cave system recently discovered by scientists. – Life has existed there for millions of years without our knowledge. With regards to the ecology of these systems, almost nothing is known. John Pohlman and his colleague, David Brankovits, are researching these cave systems to understand how life can exist here, in total darkness, and with little oxygen. – We are providing an explanation for a globally distributed ecosystem, that was unknown to science until 30 years ago. Our primary objective is to go from description of the animals inhabiting these systems to, actually, the processes that allow them to live and flourish. Our research in the Yucatan Peninsula showed that methane and other simple dissolved organic material that is trickling in from the jungle floor into the cave systems, and it's dissolved in the water, that it is being used by microbes present in the caves. No one had imagined it operated this way before. We're hoping to understand exactly how external factors related to weather, tides, hydrology, and all these things come together and wind up creating a model for how the ecosystem functions. Because these questions have never been asked before, John and David have creatively designed their own research equipment. This 300-meter copper coil will collect a small sample of water each day for six months. It will serve as a history book of the water chemistry in the cave, much like rings of a tree can indicate the history of rainfall in a forest. – This is the osmotic pump. It's the osmotic potential between this salt solution and the fresh water: this very narrow tubing will be connected into the copper coil so the water is getting pulled from the other end. This will be something that no one's ever done before. – Charged. Ready to extend. Go. It's going to be perfect. This is what we need for the field. I know that cave diving is not for everyone. I personally don't get claustrophobic, but the first time I went underwater underground it was breathtaking. What drove me was the curiosity. I wanted to see what's down there... We typically penetrate the caves up to one kilometer when we are doing research. The cavern environment is the part of the cave system where you can still see some light shining in from the sinkhole, but once you leave that zone you are in the cave that is pitch black, and the only light there is is the light that you bring with you. What's fundamentally important about these systems is that we have freshwater, with no oxygen, that contains large amounts of dissolved material that can be food, but it's not accessible to the animals living there, the microbes in particular, unless it mixes with the oxygen which is coming from beneath, with the seawater. So, once those are mixed together, you have all the ingredients for life, and then you have growth of the bacteria. And then the higher-level organisms, the crustaceans and the fish, they're feeding upon the bacteria and that's what actually is supporting the whole food web. When John and David finish this 6-month sampling period, they'll take everything back to the lab, and hopefully begin to understand this mysterious ecosystem that has been hidden under our feet for aeons. Suddenly, you see a data set that actually tells you something about the processes that sustain life in a cave system. I mean, how cool is that? Those are the moments, the wow moments, that make it worth it for me. For more episodes of Science in the Extremes, check out this one right here. Don't forget to subscribe, and come back to Seeker for more episodes. Thanks for watching!