RESPIRATORY ELECTRON-TRANSPORT SYSTEM (ETS) - ACTIVITY OF THE PLANKTON AND SEDIMENT IN LAKE BALATON (HUNGARY)

The ETS-activity of microplankton (1-60 mum), net zooplankton (60-250 mum and > 250 mum) and sediment was measured in the hypertrophic Keszthely-basin and in the meso-eutrophic Siofok-basin of Lake Balaton in 1988-1989. Six times higher microplanktonic and 1.35-1.75 times higher zooplanktonic ETS-activities l-1 were found in the Keszthely-basin than in the Siofok-basin. The equivalent relationship for the microplanktonic ETS-activity m-2 was 3.83-3.93 to 1 in 1988 and 1989. This ratio in the case of the zooplankton was 1.07-1.09 to 1. The zooplanktonic ETS-activity represented 6.0-10.8% of the total measured sestonic ETS-activity in the Keszthely-basin and 19.0-30.5% of that in the Siofok-basin in 1988 and 1989. The results suggest a decreasing trend in the contribution of net zooplankton metabolic activity in the whole metabolism of the water column with increasing primary production. The sediment was biologically active to 30-35 cm depth in the Keszthely-basin and to 15-20 cm depth in the Siofok-basin. In the Keszthely-basin and in the Siofok-basin, relative decrease in the sediment ETS-activity cm-3 with depth were 10% cm-1 and 25% cm-1 respectively. The sediment ETS-activity m-2 was much higher than that in the plankton: 7.8 times in the Keszthely-basin and 9.3 times in the Siofok-basin. The Keszthely-Siofok basins ratio for the sediment ETS-activity m-2 was 3 to 1. According to the ETS-activity data, Lake Balaton plankton itself can oxidize all the organic matter produced in the water column. The sestonic and sediment respiratory potentials together are much higher than is necessary for complete oxidation of the plankton-assimilated carbon.