Sökning: "diatoms"

Visar resultat 1 - 5 av 85 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 :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 :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. Evolutionary and Ecological Effects of Metal Pollution on Coastal Diatoms

   Författare :Björn Andersson; Göteborgs universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Phytoplankton; Diatoms; Skeletonema marinoi; Toxicity; Heavy metals; Copper; Evolution; Baltic Sea; Population genomics; Physiology; Ecology; Metabarcoding; Sedimentology; Resting stages; Dose-response relationships;

   Sammanfattning : Oceans are changing rapidly in response to human activities, such as toxic pollution, eutrophication, and climate change. Diatoms are major primary producers in the oceans with short generation times, flexible reproductive strategies, and high standing genetic diversity. LÄS MER

5. 4. 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 :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

7. 5. Origin and the evolution of diatoms through the integration of paleontology and phylogenetics

   Författare :Karolina Brylka; Berggrundsgeologi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; diatoms; evolution; fossil record; Cretaceous; molecular evolution; Mesozoic; silicon transporter proteins; gene duplication;

   Sammanfattning : Diatoms, the prominent photosynthetic eucaryotes, have inhabited the world’s oceans for at least the past 120 Ma since their first appearance in the Lower Cretaceous. There are also records of older diatoms, from the Jurassic dating to ca. 172 Ma and ca. 165 Ma, however these are poorly documented. LÄS MER