Dripping and underground river waters shed light on the ecohydrology of a show cave

Water and air flows connect underground ecosystems tothe surface, affecting the cave chemicaland physical properties. Together with the visitor’s fluxes in show caves and occasional presence of cavers in wild caves–excluding the large amounts of organic supply by bat or bird colonies or large sinking rivers bringing vegetal debris –fluid flowsare the main means of transport of nutrients into the normally oligotrophic cave environment. The aim of this work was toinvestigate the chemical characteristics of waters in the Pertosa-Auletta Cave (Italy), focusing on dripwaterand on theunderground Negro river, seasonallyand in different areas of the cave.In particular, three trailswith different environmentalcharacteristics and tourism fruition,were investigatedin order toshed light onthe processes affecting the ecological equilibriumof thehypogean ecosystem.Dripping and flowingriver waters, both rich in Ca because of their interaction with carbonate rocks, showdistinct chemical signaturesregardingthe other chemical elements (especially K and Mg)dueto lithological and hydro-dynamicaldifferences.Moreover, water chemistry is affected by the seasonality in the pluviometricregime owing to the subsequent variability in the dilution effect.Bat colonies, dwelling mainly alongthe fossil trail, enrichdripping waterswithP and N. Their concentrations have also been found at fairly high valuesacross the whole trail network, suggestingan additionalpotential role of leaching from agricultural and forested soils above the Pertosa-Auletta Cave in defining dripwaterchemistry.