CUBA'S CAVES: AN OVERVIEW OF THEIR BIOLOGY AND GEOLOGYBY TOM SAWICKI
Cuba's complex geologic history has contributed to a remarkably diverse troglobitic (cave adapted) fauna. My studies on the evolutionary history of the Hadziidae (a family of amphipod crustaceans) brought me to Cuba in order to collect specimens, and to learn more about the ecology of Cuba s caves. In the process I was privileged to explore much of Cubas beautiful countryside and make some great friends.
Approximately 50 kilometers southwest of Havana lies a large karst region. Luis Piedra Cave is one of many caves in this area that provides access to phreatic water. On January 2, 2000, I traveled to this cave along with Abel Per??z, a Cuban scientist and the only certified cave diver in Cuba. Abel had been to this cave a few years back to collect troglobitic fish and assured me that Weckelia ceca, one of the species I was in Cuba to collect, would be in this cave.
The trail leading to Luis Piedra Cave was heavily overgrown and our guides slashed a path through the underbrush with machetes. The cave entrance is a small hole in the ground that drops down approximately three meters, opening into a large cavern containing an underground lake. When we shined our lights in the water I was completely surprised by what I sawdozens of blind cave fish!
Relative to epigean ecosystems, caves are energy-poor environments. Organisms that live in caves are often dependent upon allochthonous detritus (organic material from outside the cave, such as leaves or the bodies of dead animals) to filter into the caves. This material, along with the bacteria and fungi on them, is consumed by small invertebrates, which are then consumed by other animals, like fish, salamanders or crayfish. In order to support so many fish, there would have to be a large influx of organic material into this cave, and a sizeable population of small crustaceans.
We donned our snorkel gear and hopped into the lake. All around us were hundreds of small crustaceans, including mysids and shrimp, floating in the water column. The amphipods I had come searching for were living in clumps of roots that had pushed their way through the cave ceiling and into the water column. I was amazed to see dozens of specimens living within each clump of the roots.
Generally one has to dive a locality many times just to collect a few specimens. The energy coming into Luis Piedro Cave was relatively high due to a large colony of bats living in the cavern and the tree roots, which were used not only by the amphipods, but also by a species of troglobitic crayfish. These energy sources allowed for such high species richness. We collected only a small sample in order to put as little stress on the population as possible. We then put our cave gear together and prepared to explore the cave. On his previous visit Abel limited himself to snorkeling in the lake in order to collect the troglobitic fish. This cave was virgin. After checking a couple of blind leads we found a passage that may be the beginning of a large system. We laid about 150 meters of line at an average depth of six meters. The cave just kept going. On the way out we surveyed and checked a few side passages that seemed promising. Abel tells me that there are many more such caves in this area just south of Havana and most have never been dived before. Luis Piedra was not a beautifully decorated cave, but what it lacked in geological splendor it more than made up for by its biology.
On the south coast of Cuba, a type of cave occurs that is very different from the classic solution tubes of inland Cuba. These caves are slumping fracture caves. A few hundred meters offshore from the south coast of Cuba lies a wall that was formed due to tectonic rifting. The wall drops to great depths and places stress on the karst terrain, literally pulling the limestone apart along fracture lines. These caves are rectangular in shape with sheer walls that drop off to 30 meters or more.
The caves are also anchialinehaline waters that have an inland surface connection and subterranean connections to the sea. At the halocline, a sharp drop in dissolved oxygen occurs and a very unique fauna can be found. Remipedia, (the most primitive class of crustaceans) hadziid amphipods, thermosbaenaceans, shrimp and more live in this highly-specialized environment. These caves have no speleothems and often appear unstable. I recall a few instances where I looked up and saw rocks that must have weighed tons that appeared to be hanging precariously in place. Obviously one does not wish for any tectonic activity at that moment. Most of these caves do not go very far, but the downstream side of Carboneros Cave has been pushed for approximately 300 meters and has the potential to go even farther.
The fauna that are found in Cuba s caves are very similar to what scientists find in the anchialine caves of the Yucatan and the Bahamas. Cuba may have played an important role in the distribution of fauna across the northern Caribbean. Although these animals occur in caves throughout the northern Caribbean region, individual species are often endemic to a single cave. For instance, the amphipod species, Bahazdia cubensis n.sp., is found only in Carboneros Cave. Thus, if this cave is contaminated or destroyed, B. cubensis could be lost forever.
The biological reality is also rather stark. Animals that are adapted to live in caves are highly specialized and sensitive to human perturbations. It has only been within the last few years that most of the troglobitic species living in the anchialine caves in the Caribbean region have been discovered. Anthropogenic influences are putting many of these species at risk of extinction just as we are beginning to learn of their existence. Global Underwater Explorers is dedicated to educating the public about the fragility of caves and the need for their conservation. It is up to the individual, however, to take make the effort to become more aware of the issues facing many caves. I firmly believe that those of us who use caves for our enjoyment should be actively involved in efforts to help preserve these natural wonders.