Sökning: "diatoms"

Visar resultat 1 - 5 av 78 avhandlingar innehållade ordet diatoms.

1. 1. Diatoms in Lake Duluti : Tracking Environmental Variability in Northern Tanzania during the Past 1000 Years

   Författare :Helena Öberg; Lars-Ove Westerberg; Karin Holmgren; Jan Risberg; Robert Marchant; Stockholms universitet; []
   Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Paleolimnology; Tanzania; Diatoms; Climate change; Crater lake; Physical Geography; naturgeografi;

   Sammanfattning : The tropics are the regions which are least understood climatically and new data on past climate variability is necessary for reliable future modeling of climate change. This thesis contributes with new paleoenvironmental information from a small crater lake in northern Tanzania and provides an additional link between the integrated history of climate, environment and socioeconomic variability in tropical Africa. LÄS MER

3. 2. Benthic diatoms in the Gulf of Bothnia : Community analysis and diversity

   Författare :Svenja Busse; Michael Sullivan; Uppsala universitet; []
   Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Ecology; Baltic Sea; Biodiversity; Biomass; Community ecology; Diatoms; Multivariate analysis; Navicula; Phytobenthos; Salinity gradient; Scale; Size; Water movement; Ekologi; Terrestrial; freshwater and marine ecology; Terrestisk; limnisk och marin ekologi; Ecological Botany; Ekologisk botanik;

   Sammanfattning : Benthic diatoms are valuable tools for biological monitoring and paleo-ecological reconstruction of past environmental conditions. This thesis aims at describing size-related properties of benthic diatoms and suggests that data assessment for community analysis can be improved by considering the importance of scale. LÄS MER

4. 3. Diatoms as indicators of Holocene climate and environmental change in northern Sweden

   Författare :Christian Bigler; Ingemar Renberg; Roland Hall; N. John Anderson; Umeå universitet; []
   Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Physical geography and sedimentology; diatoms; Holocene; paleolimnology; climate change; lake sediments; transfer functions; quantitative environmental reconstructions; northern Sweden; Abisko; Naturgeografi och sedimentologi; Physical geography; Naturgeografi; naturgeografi; Physical Geography;

   Sammanfattning : The objective of the thesis was to explore the potential of diatoms (Bacillariophyceae) as indicators of Holocene climate and environmental change in northern Sweden (Abisko region, 68°21'N, 18°49'E). A modern surface-sediment calibration set including 100 lakes was developed and lake-water pH, sedimentary organic content (assessed by loss-on-ignition) and temperature were identified as most powerful environmental variables explaining the variance within the diatom assemblages. LÄS MER

5. 4. Experimental Studies on the Regulation of Pigment Dynamics in Phytoplankton and Copepods by Dissolved Inorganic Nutrients

   Författare :Lies Van Nieuwerburgh; Pauli Snoeijs; Ulf Båmstedt; Uppsala universitet; []
   Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; Biology; Astaxanthin; Baltic Sea; carotenoids; diatoms; eutrophication; food web; mesocosms; microalgae; M74 syndrome; oxidative stress; phytoplankton blooms; zooplankton; Biologi; Biology; Biologi;

   Sammanfattning : This thesis examines the role of dissolved inorganic nutrients in generating changes in phytoplankton community and pigment composition and if such changes can affect the production of the antioxidant astaxanthin in the ecosystem via pelagic copepods. The background of my studies is the possible relationship between eutrophication and a reproductive disturbance in Baltic populations of Atlantic salmon (M74), which is associated with astaxanthin and thiamine deficiencies and oxidative stress. LÄS MER

7. 5. Grazer-induced responses in marine phytoplankton

   Författare :Johanna Bergkvist; Göteborgs universitet; Göteborgs universitet; Gothenburg University; []
   Nyckelord :phytoplankton; defence; dinoflagellate; diatoms; paralytic shellfish toxins; polyunsaturated aldehydes; chain formation;

   Sammanfattning : Phytoplankton are the most important primary producers in the world’s oceans, yet little is known of how they avoid the constant threats from the pelagic grazers. From land it is well known that plants defend themselves by having thorns or producing compounds unpalatable to grazers. LÄS MER