The acid drops land on our unprotected necks as we wade through sulfurous, milky waters. They sting and burn and make us twist in our sterile suits, but with hands in sterile gloves and minute quantities of sample poised on tiny instruments, we can do nothing to stop the discomfort. My colleague Diana Northup bends on one knee as she tries to tease a slimy, precious string of a bacterial slime called snottite into a tube for DNA analysis. Snottite was first found in this cave, Villa Luz in Tabasco, Mexico, and named by cave explorer Jim Pisarowicz. The snottite slips from Diana’s instrument. Her nose is itching uncontrollably behind her breathing mask, which we all must wear to avoid inhaling hydrogen sulfide. My foot, protected by an army boot, slips in the slimy, acid-soaked gypsum paste that could easily burn through my skin. I can barely keep the collecting tube under the snottite. My groin muscles are screaming in protest. We are cramped in a miserable position with bones and muscles aching, and our masks seem to bore into our skulls and faces. We long to get out of this choking place and breathe the sweet air of the surface.
 
Finally, the sample slides into the sterile tube. Capture! We have the beast! As we pack our gear, team member Kenneth Ingham, charged with monitoring the air and observing us for signs of toxicity, gives the word that the carbon monoxide level is rising and we must leave immediately. Our masks provide no protection against that deadly gas. Team member Mike Spilde sloshes hastily towards us through the milky water, where he has been taking air samples above Flema Spring as it belches out hydrogen sulfide, carbon monoxide, sulfur dioxide and carbon dioxide along with a vigorous flow of water. He is coughing.
 
We try to hurry toward the entrance, but the rocks on the stream bottom are coated with dense strings and biofilms of Thiothrix and Beggiatoa, two species of filamentous sulfur bacteria common to many sulfur-rich environments that have near-neutral pH values. We slip and the sharp rocks slice into our skin. Suddenly, Diana’s headlight winks out. No! We can’t stop yet! She follows closely on Mike’s heels, sharing his light to find her footing.
 
My skull is working on a weird headache that seems as if my brain is growing larger and my eyes are sinking in, but I am oddly detached from the feeling. The pain is an old friend and tells me we’ve been in too long. I’ve picked up a toxic load of hydrogen sulfide through my skin, and perhaps a touch of carbon monoxide poisoning as well. As we get closer to the cave’s entrance, Kenneth announces that we are away from the carbon monoxide and the hydrogen sulfide is down to a few parts per billion. We stop and gratefully rip the masks from our faces. My muscles are overwhelmed with waves of fatigue as we climb out into the Mexican sun that filters through the forest canopy.
 
So goes another day of field research in the sulfuric acid cave known as Cueva de Villa Luz. We are part of a much larger team of researchers from the United States and Mexico who are studying everything about this cave from its formation (speleogenesis) to its secondary mineralogy, its water and air chemistry, its microbiology, and the ecology of its abundant higher fauna. The sulfurous stream flows from springs in the cave to its eventual discharge through subterranean exits into a surface stream that teems with tiny fish, water bugs and small red worms. Clouds of midges seem to be feeding on a green biofilm on some of the rocks in the stream and undercuts. Five bat species have been identified in the cave. Spiders exist in staggering abundance, and many other species of invertebrates abound. The environment is harsh for us, but these microorganisms and animals thrive under the acidic, sulfurous conditions.
 
Already, we have found three previously unknown species of Thiobacillus and the DNA traces of protists and nematodes in the Villa Luz snottites. Biologist Kathy Lavoie is studying the growth rate of snottites and finds they “grow” and disappear at measurable rates. We have found that the “mud vermiculations” on some of the walls are actually live, vertical bacterial mats held together with gelatinous goo, renamed “biovermiculations” by geologist and expedition organizer Louise Hose. We have discovered numerous microorganisms growing in the acidic gypsum pastes that zero out our pH meters, fluorescent actinomycete colonies thriving happily on their surfaces. We are studying a red, claylike material dubbed “Ragu” by Diana Northup that is reminiscent of material that we are studying in Lechuguilla Cave, a very deep, very old cave in New Mexico.

Penelope Boston

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