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KOPP, R., ZIKOVA, A., MARES, J., NAVRATIL, S., ADAMOVSKÝ, O., PALIKOVA, M.: Diversity and toxin content of cyanobacteria in fi sh ponds (South Moravia, Czech Republic) related to fi shery management intensity. Acta univ. agric. et silvic. Mendel. Brun., 2008, LVI, No. 5, pp. 111–118 During the vegetative period of the year 2005 (June–October) we carried out hydrobiological and hydrochemical monitoring of selected ponds inhered in Southern Moravia in relation to diff erent fi shery management intensities. Water temperature, dissolved oxygen content, pH, conductivity and water transparency were monitored directly at taking place, N–NH4 +, N–NO2 , N–NO3 , P–PO4 3 content and chlorophyll-a concentration were measured in hydrochemical laboratory. At the same time, water samples for taxonomical analyses of phytoplankton and assessment of toxin content of cyanobacteria were taken. All ponds were characterized by low water transparency, high values of pH, N–NH4 +, P–PO4 3 and high chlorophyll a concentration. We detected maximum concentration of 18.7 μg . l−1 microcystins in ponds dominated by the species Microcystis aeruginosa. Total microcystin concentration in water of all ponds with dominance of pikoplanktonic cyanobacteria were below detection limit (LOD < 0.125 μg . l−1). The dominance of cyanobacteria species shi s from coccal (especially genus Microcystis) to small-colonial pikoplanctonic (genus Aphanocapsa, Aphanothece) and to single-fi lamentous (genus Planktothrix, Limnothrix, Pseudanabaena) cyanobacteria related to increasing fi sh stock density. cyanobacteria, ponds, fi sh stock, microcystins Fish ponds represent the most common type of stagnant water habitat in the Czech Republic and play important role in the hydrological system. The management of fi sh stock ponds did not change much for several hundred years from the middle age until the end of the nineteenth century. Since the 1950s, intensifi cation of fi sh production started, when li ming and fertilization of the fi sh ponds became a common practice. Thus, these new fi sh farming practices had an important impact on both the structure and dynamics of the aquatic ecosystem. Management of higher fi sh stock densities, accompanied by higher nutrient loads, resulted in increasing trophic status, ultimately reaching a state of hypertrophy in fi sh ponds. The main symptoms of this state are the massive development of phytoplankton and cyanobacterial blooms, great fl uctuations in oxygen concentrations and pH, and high values of ammonia nitrogen destabilizing the fi sh pond ecosystem (Komarkova, 1998; Pechar, 2000; Potužak et al., 2007). Heavy blooms of cyanobacteria are largely associated to eutrophic or hypertrophic waters. Despite objections exist concerning the validity of species indicative of a given trophic level it is evident that the assembly of species in given sites combining physical and chemical properties is far from random. An important regulatory role in the control of the biomass and species composition of the algal assemblage is aff ected by their consumers, i.e. zooplankton and fi sh stock density (Komarkova, 1998; Masojidek et al., 2001). Common carp (Cyprinus carpio L.) is the main cultivated fi sh species. High abundance of common carp may potentially aff ect the primary production and community composition of freshwater systems. Common carp, a bottom feeder, might increase the fl ux of nutrients from benthic to the pelagial zone of ponds 112 R. Kopp, A. Zikova, J. Mares, S. Navratil, O. Adamovský, M. Palikova and thus change the dominant primary producers. These changes might especially occur in shallow water (Parkos et al., 2003; Rahman et al., 2008). MATERIAL AND METHODS Monitored fi shponds are typical shallow, polymictic and hypertrophic ponds for breeding the common carp (Cyprinus carpio L.) in South Moravia (mean depth around 1.3 m, bottom containing so sediment). Data about ponds area, fi sh production and GPS localization are presented in the Table I. Water samples were taken from the outlet area of the ponds. Phytoplankton samples were taken into 100–ml plastic bottles from the depth of 0–30 cm by tube sampler. The samples were fi xed with Lugol solution and condensed in ultra-fi ltering equipment. The quantity of phytoplankton was assessed in a Burker counting chamber. Basic physico-chemical parameters (oxygen saturation of water, pH and temperature) were measured by a WTW Oxi 340i dissolved oxygen meter and a WTW pH 340i pH meter. Conductivity meter Conmet 1 by an American company Hanna Instruments was used to assess conductivity. The transparency of water was assessed with a Secchi disc. Norm ISO 10260 was used for the assessment of chlorophyll a content. Ammonia nitrogen (N–NH4) were determined by the Nessler method, nitrites (N–NO2) by the method using N–(1– naphthyl)–ethylenediamine, nitrates (N–NO3) by the method using sodium salicylate, orthophosphate (P–PO4) by the method using ascorbic acid and ammonium molybdate (APHA, 1981). Total microcystin concentration was monitored three times during the vegetative season (July, August and September) in cyanobacterial biomass and water. Concentrations of microcystins in the cyanobacterial biomass were determined by HPLC (Agilent 1100 system, Supercosil ABZ + Plus C18 column) coupled with photodiode array detector. Concentrations of microcystins in the water were determined by ELISA (Home-made Elisa according to Zeck et al., 2001) as previously described by (Blaha and Marsalek, 2003). I: Habitat description Pond Pond area ha Fish production kg . ha−1 GPS localization

Diversity and toxin content of cyanobacteria in fish ponds (South Moravia, Czech Republic) related to fishery management intensity