Isotopic indicators for the processes from the chemoautotrophic ecosystem of the Movile Cave, Romania

Measurements of the natural isotopic content for hydrogen, oxygen, sulphur and carbon for samples collected from cave served as the basis for the characterization of the cave components and processes. Based on the water isotopes, the surveys have elucidated the origin of the water from cave. The water has meteoric origin, from modern and submodern precipitation fallen over a higher altitude than that of the emergence. The cave is the buffer system between the deep confined aquifer and the unconfined aquifer from Sarmatian deposits. The δ34S values in the sulphide and sulphate from the Movile Cave and from the Black Sea present distinct values. The sulphide comes from deep aquifers and sulphate is produced in cave by sulphide oxidizing in presence of microorganisms. All forms of inorganic carbon are isotopically light. CO2 in the cave atmosphere is a mixture of heavier CO2 resulted from the dissolution of limestone and lighter CO2 resulted from the oxidization of the organic matter and/or methane. The bicarbonate in water is at isotopic equilibrium with CO2. The organisms sampled from cave are isotopically light versus surface congeners, suggesting dependence on the chemoautotrophic production occurring in cave. (author)