Hydrobotanical and hydrobiological field work was carried out at Lake Ladoga in NW Russia, mostly at Impilahti Bay in the northern part of the lake. In a shallow medium dense stand of Elodea canadensis (1452 plants.m-2; mean 192 g.m-2 of dry weight) in Impilahti Bay, between 12:00 to 18:00 hours in August 1996, the water was by 1.0–1.4 °C warmer and its pH 1.05–1.2 higher than open water. In the stand, pH increased almost to 9.0. In the same stand, water become supersaturated with O2 to 134% at midday on a sunny August day, and to only 105% on a cloudy day. The daily pH and [O2] fluctuations within the medium dense E. canadensis stand in Impilahti Bay were much less than those measured in dense stands of this species, e.g., in shallow eutrophic Czech fishponds. Communities of littoral phytophilous zooplankton, living pelagically or slightly attached on the plants, formed in the macrophyte stands. The littoral phytophilous zooplankton complex was on average 4 times more abundant and had a 38 times greater biomass per water volume (0.26–164.2 g dry weight.m-3) than that in the open water near the macrophyte communities (0.05–4.91 g dry weight.m-3) or was 3 times more abundant and had on average a 10 times greater biomass, respectively, than that in the open water in the middle of the bay. This does not accord with theory, which predicts that ecotones have the highest biodiversity and productivity.
Utricularia stygia Thor and U. intermedia Hayne are aquatic carnivorous plants with distinctly dimorphic shoots. Investment in carnivory and the morphometric characteristics of both types of shoots of these plants were determined in dense stands growing in shallow dystrophic waters in the Třeboň basin, Czech Republic, and their possible ecological regulation and interspecific differences considered. Vertical profiles of chemical and physical microhabitat factors were measured in these stands in order to differentiate key microhabitat factors associated with photosynthetic and carnivorous shoots. Total dry biomass of both species in dense stands ranged between 2.4–97.0 g·m–2. The percentage of carnivorous shoots in the total biomass, which was used as a measure of the investment in carnivory, ranged from 40–59% and that of traps from 18–29% in both species. The high percentage of total biomass made up of carnivorous shoots in both species indicates both a high structural investment in carnivory and high maintenance costs. As the mean length of the main carnivorous shoots and trap number per plant in carnivorous shoots in both species differed highly significantly between sites, it is probable that the investment in carnivory is determined by ecological factors with low water level one of the potentially most important. Marked differences were found only in [O2] between the 1–3 cm deep free-water zone with green photosynthetic shoots of both species and the 10 cm deep loose sediment with chlorophyll-free carnivorous shoots with traps (range 1.7–7.2 vs. 0.0–0.8 mg·l–1). The waters can be characterized as mesotrophic. Though anoxia occurred consistently at a depth of 10 cm in loose sediment at all U. stygia and U. intermedia sites the carnivorous shoots of both species growing in this microhabitat are able to survive and do not avoid this microhabitat.
Článek přibližuje biologické a ekologické zvláštnosti 7 našich druhů bublinatek (Utricularia), které tvoří dvojice nebo trojice velmi podobných druhů. Přináší také nové poznatky o ekofyziologických procesech v pastech vodních bublinatek. and The biological and ecological peculiarties of seven domestic species of Utricularia plants are described. These plants can be grouped on the basis of their similarity (groups of two to three similar plants). New discoveries involving the ecophysiological processes taking place in the traps of the given insectivores are also described.