Aside from providing direct access to groundwater, cenotes serve as gateways into the world's most extensive underwater cave systems. My research provides the first description of ecological and biogeochemical processes that drive the anchialine ecosystem. Primary passages are oriented along the dramatic and aggressive boundary between fresh and salt water, called a halocline, that corroded the bedrock to form the caves. Many of the caves are lavishly decorated by stalagtites and stalagmites that formed during a low sea level stand over 18,000 years ago. A unique group of organisms, cave-limited troglobites, is found in the caves.
Troglobitic bodies emphasize economy over specialty.
They have essentially reversed evolution to remove unneccessary body parts and functions. Simplified yet specialized adaptations include loss of color and eyes, the presence of long, spiny appendages, and reduced size. At present, nineteen species of Crustacea and two species of fish are known to permanently inhabit anchialine caves in the Mexican state of Quintana Roo. Organic matter needed to support the two trophic levels of the troglobitic community appears to come from three sources, two external and one internal. External sources of organic matter are the cenote pool and forest soil, while the internal source is chemosynthetic production occurring along the halocline.