Characterization of epilithic microbial communities associated with Mayan stone monuments in Yucatan, Mexico

The microbial epilithic communities associated with Uxmal Mayan stone monum ents (Yucatan, Mexico) were preliminarily characterized by chemical and bio chemical methods. The organic matter organic carbon, and nitrogen content w ere within the respective ranges reported for other stone buildings, indica ting that oligotrophic conditions prevailed at Uxmal's buildings. Quantitat ive differences in both total and phototrophic biomass were observed betwee n stone and mortar (stucco) substrata, between indoor and outdoor locations , and between seasons. Microbial biomass and organic matter content were gr eater on indoor surfaces associated with more suitable microenvironmental c onditions (availability of water and protection from direct sunlight) for m icrobial growth. Cyanobacterial photosynthesis, microbial debris, and bird droppings are the most probable sources of organic carbon and organic nitro gen in Urinal's stone buildings. The epilithic communities appear to be dom inated by phototrophs (mainly cyanobacteria) populations and associated bac teria. The latter are probably trophically dependent on the release of orga nic matter by photosynthetic production. These microbial biofilms and their activity may be responsible, in part, for the degradation of these stone m onuments.