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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Fytoplankton tatranských ples: faktory ovlivňující druhové složení a biomasu / Phytoplankton of the Tatra lakes: factors influencing taxonomic composition and biomass

Červenková, Lenka January 2010 (has links)
The aim of this diploma thesis was to describe species composition and biomass of phytoplankton in the Tatra Mountains lakes (Slovakia, Poland) and environmental factors influencing them. The surface layer of 89 lakes was sampled in September 2004. Flagellates from Chrysophyta, Dinophyta and Cryptophyta most frequently dominated the phytoplankton biomass. Lake in the same valley usually differed in their dominant taxonomic group as a result of different lake morphometry, catchment type and detailed geological structure. Based on the level of phytoplankton biovolume, the majority of lakes were ultraoligotrophic and oligotrophic, however, mesotrophic and even eutrophic conditions were recorded in some forest and meadow lakes. An allometric relationship between phytoplankton biomass and chlorophyll a was revealed. Specific chlorophyll content did not differ among taxonomic groups. Altogether 233 species were determined, the most diverse group were Chlorophyta. Species richness of lake was 3-46 and it was negatively correlated with altitude and positively correlated with lake area. The majority of species were rare both in term of biomass and number of lakes occupied by a particular species. Average local species biomass was positively correlated with regional distribution. The similarity of species...
22

Local and global contaminants in Swedish waters : studies on PCBs, DDTs, 4,5,6-trichloroguaiacol and their transformation products in fish and sediments

Söderström, Maria January 2002 (has links)
This thesis is focused on studies on the environmental fate and methodological improvements for determination of the global contaminants, PCBs and DDTs, and locally discharged phenolics, e.g. 4,5,6-trichloroguaiacol (4,5,6-TCG), and their transformation products. 4,5,6-TCG is released from bleached pulp mills, and was chosen as a model substance, to study its fate and effects in aquatic environments. In a brackish water model ecosystem, 4,5,6-TCG was shown to be transformed via demethylation, dechlorination, and methylation reactions. Marine periphyton exposed to 4,5,6-TCG was shown to form demethylated, brominated and dimeric metabolites. Several of these metabolites were identified and quantified. Also more tightly bound chlorophenolics were recovered from the substrate, after harsh extraction procedures had been applied. Conjugates of chlorophenols in fish bile were determined as useful tracers for monitoring effluents from bleached pulp mills, even in areas far from the discharge point. To facilitate calculations of water concentrations, bile to water bioconcentration factors (bBCF-values) were determined for several phenolics, including also alkali-labile chlorocatechols. PCBs and DDTs, were assessed in Swedish lakes with background exposure of these global contaminants. A methodological study focus on the contamination risks of airborne PCBs, during freeze-drying and storage of dry sediment samples. Eutrophication has been proposed to cause lower levels of pollutants in biota in lakes due to biomass dilution but in this thesis examples of higher levels of PCBs in sediment traps, sediment and in perch, and also in higher fluxes of PCBs to the sediment, were observed. Phytoplankton are supposed to be responsible for most of the transport of the contaminants. The composition of DDTs in soil, sediment traps and in dated sediment cores was studied in some detail. PCBs, DDTs, HCB and HCHs were measured in sediments from 100 reference lakes included in the National Swedish Environmental Program. The lakes have a large variation in lake characteristics, representative for different areas in Sweden. A gradient was observed for sPCB with decreasing levels from the south west towards the north. The results suggests that longrange transport is the dominating mechanism for distribution of the contaminants analysed. In this study the levles of PCBs and DDTs were lower in eutrophic lakes than in oligotrophic lakes, in an area with similar atmospheric exposure. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 6: Manuscript.</p>
23

Analys av ett urval skånska sjöars limnologiska tillstånd : En studie om kemiska och fysikaliska parametrars samvariation med växtplankton / Analysis of the limnological condition in a selection of lakes in Skåne : A study based on chemical and physical parameters and their covariation with phytoplankton

Johannesson, Marlene January 2021 (has links)
Svenska sjöars trofistatus delas upp i fyra olika statusar; oligotrofa, mesotrofa, eutrofa och hypertrofa. Försurning och övergödning är vanligt, till följd av antingen naturliga eller antropogena orsaker. Syftet med studien var att undersöka hur plankton (biodensitet) samvarierar med olika kemiska och fysikaliska parametrar (pH, konduktivitet, vattenfärg, turbiditet, siktdjup, Tot-N och Tot-P) i 20 skånska sjöar, samt hur biodensiteten skiljer sig mellan trofistatusarna. Syftet var även att bedöma sjöarnas tillstånd utifrån parametrarna, plankton som bioindikator, tidigare miljöövervakningar och bedömningsgrunder. Studienomfattade fältarbete där vatten- och planktonprov samlades in och vattenanalyser av siktdjup, pH och konduktivitet utfördes. På labb analyserades biodensiteten genom flödescytometri, planktonartbestämning genom mikroskopering och analyser av vattenfärg, turbiditet, Tot-N och Tot-P. En databasanvändes för att bedöma sjöarnas trofistatus och som kontroll vid analys av biodensiteten mellan trofistatusarna. Statistiska analyser utfördes för att analysera data. Biodensiteten kan förklaras till 71,1% av både vattenfärg och Tot-P. Multikollinearitet kan ha bidragit till ett felaktigt icke-signifikant samband mellan biodensitet och parametrarna turbiditet och Tot-N. Biodensiteten skiljde sig inte signifikant åt mellan trofistatusarna, vilket kan bero på provstorleken. De tidigare bedömningsgrunder och de nya av vattendirektivet skiljde sig åt för några parametrar. En uppmaning är att studera skånska sjöar med vattendirektivets bedömningsgrunder för att bibehålla en god miljöövervakning och uppnå miljömålen, och att lägga till konduktivitet samt återinföra turbiditet och vattenfärg i bedömningsgrunderna. / Swedish lakes’ trophy status is divided into oligotrophic, mesotrophic, eutrophic, and hypertrophic. Acidification and eutrophication are common, due to either natural or anthropogenic causes. The purpose of the study was to investigate how plankton (biodensity) covaries with chemical and physical parameters (pH, conductivity, watercolor, turbidity, visibility depth, Tot-N and Tot-P) in 20 lakes in Skåne, and how the biodensity differs between trophy levels. The purpose was also to assess the lake conditions based on the previously mentioned parameters, previous environmental monitoring, and assessment criteria. The study included fieldwork where water samples were collected, and water analyzes of visibility depth, pH and conductivity were performed. In the lab, plankton was analyzed by flow cytometry and microscopy,and watercolor, turbidity, Tot-N and Tot-P by water analyses. A database was used to assess the lakes’ trophy status and as a control when analyzing the biodensity between the trophy statuses. Statistical analyzes were performed to analyze data. 71,1% of the biodensity’s variation was explained by watercolor and Tot-P. Multicollinearity may have contributed to an incorrectly insignificant correlation between biodensity, turbidity and Tot-N. The biodensity did not differ between the trophy statuses, which mightdepend on the sample size. The previous assessment criteria and the new ones of the Water Framework Directive (WFD) differed for some parameters. A recommendation is to study lakes in Skåne with the WFD’s assessment criteria to maintain a good environmental monitoring and to achieve the environmental goals, and to add conductivity and reintroduce turbidity and watercolor into the assessment criteria.
24

Anabaena - Phenotypic and genotypic diversity of planktonic strains in fishponds and reservoirs of the Czech Republic / Anabaena - Phenotypic and genotypic diversity of planktonic strains in fishponds and reservoirs of the Czech Republic

ZAPOMĚLOVÁ, Eliška January 2008 (has links)
Morphological diversity of 61 Anabaena populations of 13 morphospecies was described under the field conditions of Czech fishponds and reservoirs. Polyphasic approach was then applied in classification of 45 clonal strains isolated from those populations. Detailed morphological analyses were performed and partial 16S rRNA gene sequences were obtained for 33 of the strains, and secondary metabolite production was evaluated in 20 strains. Plasticity of morphological characteristics under varied conditions of light, temperature, nitrogen and phosphorus was studied in selected strains, as well as their temperature and light growth requirements. The results were then discussed with respect to the delimitation of single Anabaena morphospecies. A new genus Sphaerospermum was defined for the morphospecies Anabaena kisseleviana, A. reniformis and Aphanizomenon aphanizomenoides, whose phenotypic and genotypic features differed considerably from all other Anabaena morphospecies. Unique information was provided on the occurrence and distribution of A. reniformis and Aph. aphanizomenoides in the Czech Republic.

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