They look like places of unspoiled nature, yet even the underground caves dug in the heart of the mountains can be polluted by bacteria from the waste water of cities and agricultural areas. This is demonstrated by the analyzes conducted in the karst system of the Monte Conca nature reserve in Sicily by researchers from the University of South Florida in collaboration with the Speleological Center of Etna. The results are published in the journal Plos One.
Geologists and microbiologists worked side by side to collect and analyze samples of the waters that flow inside the caves. They found that they have very different bacteria over the year. During the dry season, oxidizing sulfur bacteria are mostly found, which proliferate thanks to the oxygen present in the caves and the hydrogen sulphide of the waters. After heavy rains, these bacteria are replaced by other microorganisms usually present on the surface and due to man, such as Escherichia coli and other faecal bacteria. An intermediate condition of transition between the two seasons was observed in one of the samples, in which there were contaminants of human origin, oxidizing sulfur bacteria and nitrogen fixing bacteria, all together. From these results, the researchers deduce that the contaminants derive from surface waters which, after passing through urban and agricultural areas, end up filtering in the underground cave system.
