Ingestion Rates of Some Daphnia Species in a Shallow Lake (Lake Balaton, Hungary)

Filtering rates of three species of Daphnia were studied in situ by the 14 C technique during the summer in a lake with a water temperature of 20‐25°C (Lake Balaton, Hungary). The renewal time of gut contents proved to be 3‐5 min in each of the three species whether fed on natural or artificial food. From May to September, filtering rates of D. cucullata, D. hyalina and D. galeata averaged 7.8, 10.3 and 9.2 ml ind. −1 day −1 , respectively. Identically long individuals of all three species had almost the same filtering rates in spring, whereas in summer animals of identical weights had similar filtering rates regardless of species because of the length variability of the helmets. The grazing rate of adult filter‐feeding crustaceans is suggested to be approximately 7 % per day.