On the carbon and sulphur metabolism in the meromictic Lake Faro (Sicily)

Abstract

The processes of photosynthesis, chemosynthesis and sulphate reduction were quantitatively studied in the brackish meromitic lake Faro (Sicily) with the aid of C¹⁴ and S³⁵. The layer of “red water” was situated at the depht of the chemocline (13–14 m), where the average concentration of H₂S was 10 mg/l. The total biomass of bacterioplankton consisted in this layer mostly of a brown Chlorobium which reached a wet weight of 30 g/m³. The production of photosynthesis in this layer was 30–60 µg C/l/day. The microbial population in the “red water” was found adapted to an extremely low light intensity and to show a light optimum at the depth µg 9m where only 2,5% of outside light penetrates. The photoautotrophic microflora is consumed by infusoria found in mass in the “red water” layer. An active H₂S-production was found in the water column in the upper part of the H₂S-zone and in the bottom sediments. The data are discussed from the view point of the trophology of meromitic basins.