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Induction of extracelullar phosphatases in acidotolerant planktonic algae from the genus Coccomyxa: impact of phosphorus concentration and form
Macholdová, Markéta ; Nedbalová, Linda (advisor) ; Ševců, Alena (referee)
Phosphorus is frequently a limiting factor for phytoplankton in freshwater ecosystems, because algae and cyanobacteria are able to incorporate it only in a dissolved inorganic form. Phytoplankton evolved several mechanisms to overcome phosphorus limitation. One of them is the production of extracellular phosphatases. These enzymes are excreted on the surface of cells or released to the environment. They hydrolyze organic molecules containing phosphorus, which can be then incorporated by cells. This mechanism can influence the competitiveness of algae living in environments that are characterised by long-term phosphorus limitation (that is caused e.g. by the effect of low pH). In this study the influence of phosphorus concentration and form on extracellular phosphatase activity under laboratory conditions was investigated. The two experimental strains of the genus Coccomyxa (Chlorophyta) were isolated from acidified localities with different phosphorus availability Plešné Lake and Hromnické Lake. Extracellular phosphatase activity on a single-cell level was measured using the FLEA technique and fluorescence microscopy. The FLEA technique allows direct visualization of phosphatases on the cell surface by incubating the samples with the artificial substrate ELF® 97 phosphate. Extracellular...
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Taxonomic position, phylogenetic relationships and metal resistance of green algae dominating in phytoplankton of two acid lakes
Barcyte, Dovile ; Nedbalová, Linda (advisor) ; Hašler, Petr (referee)
The aim of this diploma thesis was to reveal the taxonomic position and phylogenetic relationships of the dominant planktonic algae in two acid metal-rich lakes (Hromnice Lake and Plešné Lake, Czech Republic) and to compare these isolates with other closely related strains with the focus on the tolerance to various toxic metals (Cr, Al, Cu, Mn, Zn, Hg). The phylogenetic analyses showed that both strains belong to species Coccomyxa simplex. It was the first evidence that specifically this species is capable to become the dominant phytoplankton alga in the extreme environment of acid lakes with increased supply of phosphorus. Based on 18S rDNA analysis, four independent phylogenetic lineages were revealed within the genus Coccomyxa with three of them containing isolates from acid freshwaters. Furthermore, new strains of the recently described species Coccomyxa polymorpha were found growing in various chemical solutions. The toxicity test revealed that Coccomyxa simplex strains isolated from Hromnice and Plešné lakes did not show any peculiar resistance to increased metal concentrations. A significantly strain-specific response was recorded in case of aluminum, however, it was not related to the concentration of this metal in the original habitat. The ability to thrive in extreme habitats is probably...
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Food quality impact on growth and survival of Daphnia longispina (Crustacea: Cladocera)
Sýkorová, Veronika ; Sacherová, Veronika (advisor) ; Macháček, Jiří (referee)
This thesis focuses on ecological processes among plankton organisms. It especially questions the influence of food quality on growth and survival of freshwater plankton. I focused on the influence of various ratios of nitrogen and phosphorus in available food. I am also interested in finding out the food requirements of chosen consumer Daphnia longispina. Within this broad topic, I specify a question, whether various quality and quantity of food influences the life history parameters of the species Daphnia longispina and whether the absence of common species of Cladoceran Daphnia longispina in Plešné Lake is caused by unsuitable quality of food. I have bred Daphnia longispina in laboratory conditions for two years. I fed it by algae Monoraphidium dybowskii isolated from Plešné Lake and grown in two media P-limited (C:P 1174), P-unlimited (C:P 290) and three concentration (1,2, 4 mg C/L). Cladocerans fed by food from medium that had a C:N:P ratio approximately the same as can be found in Plešné Lake (C:P 1174) lived for a singificantly shorter period of time and during the experiment they did not reproduce even in the case with the largest amount of food (4 mg C/L). This is a possible reason why Daphnia longispina did not return to Plešné Lake after the period of strong acidification, climax of...
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