Potential food resources for aquatic birds in sodic waters

Abstract

In 2002 we investigated the invertebrate macrofauna of sodic waters of HNP, KNP and FHNP, for the purpose to estimate the food supplies for the famous aquatic bird populations of these national parks. Chemical data showed that the majority of the waters belong to the oligo-mesohaline category, for their salinity changed between 0.4 and 2.2, and pH-values were high as well. Hemimetabolic benthic animals were only sporadically encountered, as also the newest investigations showed that the whole benthic fauna of sodic waters was very poor. The bottom was only populated by small number of Chironomids and Annelids. In contrast to benthos, metaphitic organisms were found in greater individual and species numbers in sodic waters. Characteristic sodic-halophilic creatures were beetles, non-biting midges and soldier flies. In black sodic waters two Chaoborus species have been found. Caddisflies were represented by only five species. On the windy side (which is a concentrated feeding place) of inundated sodic ponds of Lake Fertő, the main ecologic effect was exerted by the wave. The whole insect biomass was concentrated in the resuspended sediment, and this was well utilized by the birds. Chironomid larvae are twisted ring wise and move synchronously with the wind-borne slurry bay-bar. At these places, the animal biomass was highly concentrated, whereas other places of the turbid, white sodic waters were almost empty.