FILAMENTOUS ALGAE IN FISH PONDS OF THE TREBON BIOSPHERE RESERVE - ECOPHYSIOLOGICAL STUDY

Filamentous algae in eutrophic carp ponds in South Bohemia (Central Eu rope) were studied from 1988 to 1990. High biomass (490 g DW m(-2)) wa s attained by Cladophora fracta (O. E Mull. ex Vahl) Kutz. after two m onths of growth. This marked growth depleted inorganic carbon in the w ater, but did not decrease the concentration of tissue nutrients. Labo ratory measurements of final pH indicate that all the filamentous alga e studied, except for Tribonema, are very efficient HCO3- users. An ex tremely high pH of 11.6 and oxygen concentration of 32 mg l(-1) were m easured in the algal mats. High pH resulted in CaCO3 precipitation, vi sible as white incrustations on algal filaments. The amount of precipi tated CaCO3 reached 134 kg ha(-1). After reaching peak biomass, 90% of the Cladophora decomposed over the next 95 days. The highest net phot osynthetic rate in C. fracta was measured between pH range 8.5-10.0 an d oxygen concentrations of 7-12 mg l(-1). Optimum temperature for phot osynthesis was between 17-22 degrees C.