Dr. Fűköh Levente szerk.: Malakológiai Tájékoztató 9. (Eger, 1990.)
Szabó Sándor: Malakológiai megfigyelések a Háromszögi-tóban (1978-1989 között)
Szabó Sándor: MALAKOLÚGICAL OBSERVATIONS ON THE HÁROMSZÖGI-TÓ (1978 TO 1989) ABSTRACT : " Ouring the malakológical research of the sodic Háromszögi-tó 21 species have been found. Recently 12 species exist in the lake. After a long period of dryness the lake is regaining its fauna again. Its seems that the species have survived during the long and uncongenial period in the wet silt. The Háromszögi-tó (Triangle Lake) is north of Kunszentmiklós, about 4 kms from the National Parks of Kiskunság. In this work of mine I summarize the experiences of my collecting until vow. The lake is the northest one of the saliferous lakes of the region between the Danube and Tisza. It actually developed from the remains of one of former branches of the Danube. The water level (having reached 2...3 meters at the at the beginning of this century (was significantly lowered by the regulation of water-ways in the thirties. Its water s drained by the Main Channel of the Danube valley (the so called "Curse Channel") throungh channels XXXIII. and XXXI...The Háromszögi-tó is of about 3 hectares territory in a nearly pear formed bed. Its eastern shore was heightened with a dam, and a sluice was built on channel XXXIII. (which hasn't ever been in use. (The lake is surrounded by plough-lands on the southern and northern loesses shore and by sodic lowland on its eastern and western shores. During the period under survey the water took 40 \ of the original bed. The maximum depth of water plumbed by me was 80 cms. The kale is bordered by Phragmites at a width of 10..25 m and jby Thypa at deeper parts. In the middle of the lake about 10H of the whole territqry is taken by open surface of water, which has already been separated into !two parts by Phragmites , pressing forward lately. In earlier times Ulothrix, Hottonia, Ceratophyllum and Myriophyllum of the float reedgrasses were observed. Recently fn the lake there are only Ulothrix , while Ceratophyllum and Myr.iophy Hum exist only in the outgoing channel. The water of the lake belonged to the "white water" type of sodic lakes in the starking period of survey. Of late years the water of the lake turned into a f'black water" type due to eutrofizatiqn is in consequense of the accumulation of putrescent organic matters. The pH-'valUe of the lake was between 7,2 and 9,5. The pH-value increased in inverse ratio to the decrease of the water. The water metabolism of the lake is immoderate. From 1980 to 19B8 exept some weeks in spring it was almost dried put. I collected soil and silt amples by square method and that of wa ter-courses . Results: During the period of surviey 919individuals of 21 species were collected. 46,4 \ of all types of molluscs (water species) in Upper Little Cumania. (SZABÓ, 1980). Fossil sediment 5 to 10 cms thick can be observed for some metres of the south-east excavated lake wall. After sluicing the samples from the sediment individuals of 10 species were found. ;A11 terrestrial species exist in the recent fauna. No Valvata piscinalis, Lithoglipus naticoides and Bithynia tentaculata exitis in the lake. Appealing of Lithogliphus naticoides proves the lake having a fluvial origin.
