title: Summer changes in cyanobacterial bloom composition and microcystin concentration in eutrophic Czech reservoirs.
abstract: In mid-July and August 2003 and 2004, 18 reservoirs in the Czech Republic were sampled for phytoplankton species composition and concentration of intracellular microcystins (MCs). As a consequence of high nutrient loading, most of the reservoirs experienced cyanobacterial blooms of various intensities, with the prevalence of cyanobacteria increasing markedly in August, along with a conspicuous shift in species composition toward dominance of Microcystis spp. Microcystins were detected in 90% of the samples, and their amount also increased considerably in August, reflecting the cyanobacterial biomass. In Microcystis-dominated samples, a significantly higher amount of MCs (p < 0.001) occurred than in samples in which other taxa prevailed. Microcystins were positively correlated with chlorophyll a and cyanobacterial biovolume (p < 0.05, R2 = 0.61 and 0.66, respectively), with the strongest correlation found for Microcystis spp. biovolume (p < 0.001, R2 = 0.87). This taxon was the most important producer of MCs in Czech reservoirs. The main structural variants of MCs were MC-LR, MC-RR, and MC-YR. This study's data also indicate that the relative share of MC variants (MC-LR and MC-RR) varies considerably with time, most likely as a consequence of different species and strain compositions during the summer. This study clearly demonstrates a high prevalence of MC-producing cyanobacteria in Czech reservoirs. Therefore, regular monitoring of these reservoirs is highly desirable in an effort to minimize potential health risks to the human population.
authors.affiliation: Laboratory of Phytoplankton Ecology, Hydrobiological Institute of Czech Academy of Sciences, Na Sádkách 7, CZ-37005 Ceské Budejovice, Czech Republic. znachy@hbu.cas.cz
authors.forename: Petr
authors.initials: P
authors.lastname: Znachor
authors.forename: Tomasz
authors.initials: T
authors.lastname: Jurczak
authors.forename: Jaroslava
authors.initials: J
authors.lastname: Komárková
authors.forename: Jitka
authors.initials: J
authors.lastname: Jezberová
authors.forename: Joanna
authors.initials: J
authors.lastname: Mankiewicz
authors.forename: Klára
authors.initials: K
authors.lastname: Kastovská
authors.forename: Eliska
authors.initials: E
authors.lastname: Zapomelová
mesh_terms: D018533:Biomass; D000458:Cyanobacteria / Q000254:growth & development*; D018153:Czech Republic; D004784:Environmental Monitoring; D005068:Eutrophication; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D052998:Microcystins; D010456:Peptides, Cyclic / Q000378:metabolism*; D011157:Population Dynamics; D012621:Seasons; D014871:Water Microbiology; D014881:Water Supply
chemical_list: D052998:Microcystins; D010456:Peptides, Cyclic; C078588:microcystin