Dr. Fűköh Levente szerk.: Malakológiai Tájékoztató 12. (Eger, 1993.)

SZABÓ, S.: The effect of becoming waterless and experiments of livingplace reconstraction on Monusca living in the soid laces of Upper Kiskunság

Kelemenszék In this lake there are species - with big body - only near the fresh water coming from the canal. The snailbiomassa of the lake - in view of the whole lake - is very low it doesn't reach one tenth value of the "Fehérszék". Lake Kisréti In the reeds and in the hardly any deep water the big bodies species are breeded quite well. Just only the Anisus spirorbis live in the opened water. The difference of snailbiomassa is more than 70 times here as welle. Zabszék, Pipásszék Practically only the Anisus spirorbis live in these lakes. The snailbiomassa is extremely low and in the opened waters it is insignificant, and it doesn't reach one fiftieth of the Fehérszék's. Change of snailbiomassa Locally: The biomassa of reeds is always higher than the opened waters, except Fehérszék. It comes from the nourishment - the species with big body are mostly detritus eaters - and the chemical connection of water. The snailbiomassa is decreased desperately by increase of water's pH value, electric conductivity (total salinity) and Na2C03 amount. Aggregate: The livingplace reconstructional territories and parts having foreign" water occasionally have higher snailbiomassa considerably. The reason for this higher snailbiomassa is the reduction of watersalinity. The waters hardly reach the 900 S conductivity value which is typically minimum in case of salines. The snailbiomassa of Fehérszék is shown tendency of successional changes. In the high salinity, and 5000 - 12 000 S conductivity of "Zabszék" and "Pipásszék" the coenosys and biomassa is similar to the value of 1970's. Summation: A) The water reduction and desiccation of sodic lakes cause extinction of some species in large numbers but in case of characteristic species the survival is solved by periodic return of water. B) The proved escaping factors are till now: drastic reduction of water, pH value above 9, Na2CC»3 amount of water risen at least above 25mg/l. C) The species stay in the 10-15 cm deep mud under the surface during the total parching, the species with bigger body go into the polygonal rents of the soil or into the still existing deeper marshy parts during the drought. D) In consequence of returning water mollusc start to return slowly from the oecological refugiums being deeper parts of ex-livingplaces. E) During the livingplace reconstruction the settlement of mollusc from the alimentary canals can be experienced. F) As a method of measuring snailbiomassa the Haarlow-index can be applied well. In the sodic lakes of Upper Kiskunság the extremeties of snailbiomassa are determined by the flora and the chemical connection of water.