Sökning: "food web"

Visar resultat 11 - 15 av 175 avhandlingar innehållade orden food web.

1. 11. Mechanisms structuring the pelagic microbial food web : Importance of resource and predation

   Författare :Kristina Samuelsson; Agneta Andersson; Christiane Lancelot; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Ecology; pelagic microbial food web; bacteria; flagellates; ciliates; phytoplankton; mixotrophy; nutrient status; predation limitation; resource limitation; Baltic Sea; Ekologi; Terrestrial; freshwater and marine ecology; Terrestisk; limnisk och marin ekologi;

   Sammanfattning : Temporal and spatial variations of pelagic microorganisms in the northern Baltic Sea were studied, as well as factors influencing their abundance and growth rates. Three main questions were asked 1) How does increased productivity influence the structure of the microbial food web? 2) Does predation limitation vary between trophic levels? 3) What is the relative importance of resource and predation limitation at different trophic levels?A field study in the northern Baltic Sea showed that dominating protozoa, flagellates and ciliates, increased with increasing primary productivity from north to south. LÄS MER

3. 12. Dynamics of astaxanthin, tocopherol (Vitamin E) and thiamine (Vitamin B1) in the Baltic Sea ecosystem : Bottom-up effects in an aquatic food web

   Författare :Norbert Häubner; Pauli Snoeijs; Jon Ågren; Rhena Schumann; Markku Viitasalo; Uppsala universitet; []
   Nyckelord :Baltic Sea; carotenoids; astaxanthin; tocopherols; Vitamin E; thiamine; Vitamin B1; pelagic food web; eutrophication; M74; phytoplankton; zooplankton; sprat; Sprattus sprattus balticus; herring; Clupea harengus; salmon; Salmo salar; cod; Gadus morhua; High Performance Liquid Chromatography HPLC ; electrochemical detection ECD ;

   Sammanfattning : The thesis combines laboratory experiments and field expeditions to study production, transfer and consumption of non-enzymatic antioxidants and thiamine in an aquatic food web. In particular, I (1) documented spatial and seasonal variation of tocopherols and carotenoids in the Baltic Sea pelagic food web, and (2) examined the effects of abiotic and biotic factors on tocopherol, carotenoid and thiamine concentrations in phytoplankton, zooplankton and fish. LÄS MER

4. 13. Food Safety Learning in Home and Consumer Studies : Teachers' and Students' Perspectives

   Författare :Marie Lange; Ingela Marklinder; Helen Göranzon; Chris Griffith; Uppsala universitet; []
   Nyckelord :Learning; Food safety; Education; Didactic; Risk; Food hygiene; Trust; Students ; Teachers ; Compulsory school; Kostvetenskap; Food; Nutrition and Dietetics;

   Sammanfattning : The aim of this thesis was to explore food safety as part of Home and consumer studies (HCS) education in Swedish compulsory school.Firstly, a nationwide web-based questionnaire was performed among HCS teachers to obtain an overall picture of their knowledge, behaviour and attitudes regarding food safety. LÄS MER

5. 14. Food Web Ecology -- individual life-histories and ecological processes shape complex communities

   Författare :Martin Hartvig; Evolutionär ekologi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; food web; community ecology; community assembly; size-structure; life-history omnivory; ontogeny; trophic interactions; trait based model; topology; emergent organisation; size-spectrum;

   Sammanfattning : This thesis sets out a food web framework for size-structured populations. The framework enables an ecological approach to food web modelling as the individual life-history from birth, through maturation, and ultimately death is explicitly resolved with the use of bioenergetics based on individual body size. LÄS MER

7. 15. Food Webs, Models and Species Extinctions in a Stochastic Environment

   Författare :Patrik Karlsson; Biologiska institutionen; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Ekologi; Ecology; functional redundancy; trophospecies; species aggregation; environmental stochasticity; interaction strength; spectral colour; food web structure; food webs; extinction risk;

   Sammanfattning : In light of the current global mass extinction of species, ecologists are facing great challenges. In order to reverse the path towards additional extinctions early warning systems to guide management actions need to be developed. LÄS MER