Récés-szék, Sodic Pan with Ducks
This area contains the only remaining alkaline lakes more or less preserved in their natural state. Depending on the water level, the surface area can encompass anywhere between 3 and 7 hectares. Alkaline lakes in general are a particular type of surface water. Depending on the weather and the season, water can inundate several to several hundred hectares. During the dry, rainless summer, the water dries up. In years of drought, salt crystals “bloom” into salt licks on the surface of the soil. This used to be collected for use as laundry detergent.
Since the lakes are always alkaline, the flora and fauna is unique. Only a few salt-tolerant species are capable of surviving in such conditions. Large populations of microscopic crayfish sometimes appear. Some bird species specifically scout for such locations because of the valuable food to be found in the waters. The highly saline waters are often dull white in colour, and for this reason are called “white lakes.” The Great Southern Plain was once rich in salt lakes. However, these days a name may be the only surviving indication that a lake once stood there. When the lakes dried up, the basins were converted to fishponds where summer cottages sprung up on the shores.
The most populous group of invertebrate fauna in the turbid waters of the alkaline lakes are the mesozooplankton (100-1000μm), primarily copepods and water fleas (Cladocera)
During the summer, the concentration of species is significantly reduced. Even so, the density of the small salt-tolerant crustaceans can reach up to 8000-10000/litre.
The larger-bodied macrozooplankton (1mm-2 cm) appear in the saline waters in early spring. The Brachinecta orientalis is a typical species found in the eastern lakes (see photo). Shallows resulting from the summer desiccation concentrate thick masses of zooplankton, attracting large numbers of different shore birds.
Predatory dragonflies’ larvae develop in the shallows under cover of the coastal vegetation. The damselfly (Lestes macrostigma) is particular to saline environments such as this (see photo). Smaller insects such as biting midge larvae, and the larvae of non-biting midges inhabit the undergrowth. During the summer, hordes of various fly species appear in the dehydrated mud pools. Larvae growing in the mud form an important source of nutrients for long-billed shorebirds.
Large numbers of water scavenger beetles (Hydrophilidae) are found in the saline waters.
The most typical species include Sigara assimilis and S. lateralis (photo). Diving beetle larvae live on the surface of the substrate, while adult beetles live typical aquatic lives. Of these, the Bidessus nasutus is of particular interest.