Respiratory electron transport system (ETS)-activity of the plankton and biofilm in the high-mountain lake La Caldera (Sierra Nevada, Spain)

Abstract

Quantity and ETS-activity of the plankton and those of the biofilm in the high-mountain lake La Caldera (altitude: 3040 m a.s.l.) were studied in August-September, 1992 and 1993. The quantity of the biofilm, covering the bed stones sometimes reached 1 kg wet mass m -2 . Its ETS-activity exceeded by 2.5-5 times, that of the phytoplankton and, by 8.33-22 times, that of the zooplankton, projecting 1 m 2 surface area of the lake. The substrate kinetics of its ETS suggested eucaryotic property. The plankton concentrated in the deeper water in day time and elevated to the upper water layers by evenings. The daily respiratory carbon loss of the zooplankton, estimated from the ETS-activity was equivalent with 34-38 % of the planktonic primary production. The results indicated that the metabolically most active zone was forced to the profound, probably by the intensive UV-b radiation.