The Distribution of H^S in the Lake of Faro 203 



ing. In this respect, we must point out that the new canal named 

 "degh Inglesi" connecting the lake to the Tyrrhenian Sea had 

 just been opened a few days l^efore. It must therefore be sup- 

 posed that such a crisis was due to the new supply of sea-water, 

 which, entering at a certain rate, caused a mixing in the middle 

 layer of the water. It is quite probable that such mixing and 

 not an abnormal production of HuS, caused the above crisis, 

 considering that, in the deepest layers, the quantity of HjS 

 remained almost constant during all the period of investigations. 

 In confirmation of this, notice that we had the same phenomenon, 

 although on a minor scale, in January 1961, by opening of the 

 canal, previously closed for a long time because of rough sea. 



SUM31ARY 



The changes in the quantitative distribution and stratification 

 of hydrogen sulphide, present in the brackish lake of Faro from 

 a certain depth down to the bottom, were followed, during a 

 full year. In the period between April and July 1960 the transi- 

 tion zone between the higher layer containing O^ and the lower 

 one containing Hi;S remained at an almost constant depth of 

 9 m. In this period, in the zone lying immediately below, the 

 "red water," about 1 m thickness, was constantly found. Data 

 were obtained also on counts of sulphate-reducing bacteria and 

 on bacteriological tests with the Winogradsky culture-aquarium. 



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