title: Massive occurrence of heterotrophic filaments in acidified lakes: seasonal dynamics and composition.
abstract: We documented permanent presence of heterotrophic filaments in three acidified lakes (pH<5) in the Bohemian Forest. Due to acidification, crustacean zooplankton were absent in all but one lake. In terms of carbon flow, microorganisms were thus almost exclusive players in the pelagic food webs. Variety of extremely long (>100 microm) heterotrophic filaments occurred in the lakes. The filaments usually accounted for >50% of total heterotrophic microbial biomass in the pelagic zone (medians of the total biomass: 82-108 microg C l(-1)), except for anoxic bottom layers and for episodic appearance of Daphnia longispina in one lake. Seasonal filament formation was mainly induced and maintained by grazing of mixotrophic flagellates (Dinobryon spp.) on small unicellular bacteria in the absence of cladoceran filtration. The filaments were less active than unicellular suspended bacteria. Fluorescence in situ hybridisation revealed that usually <50% of total bacteria were targeted with oligonucleotide probes for Eubacteria.
authors.affiliation: Hydrobiological Institute AS CR, Na Sádkách 7, CZ-37005 Ceské Budejovice, Czech Republic. vrba@hbu.cas.cz
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Vrba
authors.forename: Jirí
authors.initials: J
authors.lastname: Nedoma
authors.forename: Leos
authors.initials: L
authors.lastname: Kohout
authors.forename: Jirí
authors.initials: J
authors.lastname: Kopácek
authors.forename: Linda
authors.initials: L
authors.lastname: Nedbalová
authors.forename: Petra
authors.initials: P
authors.lastname: Rácková
authors.forename: Karel
authors.initials: K
authors.lastname: Simek