Stygofauna abundance and distribution in the fissures and caves of the Nardo (southern Italy) fractured aquifer subject to reclaimed water injections

The demographic growth in developing countries and the increasing pressure of anthropological activities in industrialized states around the world, are leading to a gradual contamination of the natural habitats of our planet. Although the extent of these effects is unclear, the results can already seen in the quality of natural resources, which are intensely stressed by climate changes (greenhouse effect, nutrients load, water consumption, etc.) and by direct contamination of toxic wastes. This could progressively destroy the variety of faunal species and, indeed, recent warming has caused changes in species distribution and abundance. This paper presents an investigation into the possible effects of climate change and anthropological pressures on the ground water fauna present at the Nardo site (Salento peninsula, Southern Italy). Three ecological categories were examined: stygoxenes, stygophiles and stygobionts. The latter are anophthalmic, without pigment, measure up to 10-12 mm, and live in water which moves throughout fissures and karstic caves of carbonate aquifers. These stygofauna are very sensitive to changes, due to environmental stresses, such as water temperature, dissolved oxygen, water salinity, pH and chemical constituents, in their hypogeous habitat. The stygofauna categories are active organisms which contribute to the biodegradation of organic compounds in wastewater artificially (or naturally) injected in the fractured subsoil. Weak information has been available until now about Salento stygofauna ability to resist water pollution caused by human activities. At the Nardo site 12000 m(3)/d of 2(y) effluent from municipal treatment plants have been injected since 1991 in a natural sinkhole. Here, the abundance of the stygofauna, recovered in three wells (Colucci, Brusca and Spundurata cave) at progressive distances from sinkhole, and their distribution have been correlated with ground water constituents. Ground-water quality was monitored on each occasion that stygofauna were collected, during the spring-autumn seasons.