A survey of the algal flora of anthropogenic caves of Campi Flegrei (Naples, Italy) archeological district.

Campi Flegrei is a large volcanic area situated northwest of Naples, Italy. Two archeological sites, the Sybil’s Cave and the Piscina Mirabilis, are artificial caves dug in the yellow tuff and used during antiquity for various purposes. This paper describes for the first time the algal biodiversity of these caves and determines whether environmental factors such as light intensity and humidity are influential in species distribution. A total of twenty-two algal species were identified by molecular methods (18S rDNA); the largest group was Cyanobacteria (eleven species), followed by algae Chlorophyta (six), Rhodophyta (two) and Bacillariophyta (two). Cluster analysis of algal distribution in the caves in relation to light and humidity showed no relevant differences in algal distribution between the two caves. Three different algal groups were identified. The first one includes strains strictly dependent on low humidity, a second cluster was mainly associated with sites where humidity is not a severe constraint, and a third group, mainly represented by filamentous cyanobacteria, is probably dependent on high humidity, since it was detected only at Piscina Mirabilis.