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Visar resultat 16 - 20 av 32 avhandlingar som matchar ovanstående sökkriterier.

1. 16. Productivity and carbon transfer in pelagic food webs in response to carbon, nutrients and light

   Författare :Carolyn Faithfull; Ann-Kristin Bergström; Tobias Vrede; Kathryn Cottingham; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; bacterial production; phytoplankton production; mesocosms; food webs; carbon; nutrients; light; Terrestrial; freshwater and marine ecology; Terrestrisk; limnisk och marin ekologi; limnologi; Limnology;

   Sammanfattning : Some of the major problems we face today are human induced changes to the nitrogen (N), phosphorus (P) and carbon (C) cycles. Predicted increases in rainfall and temperature due to climate change, may also increase dissolved organic matter (DOM) inflows to freshwater ecosystems in the boreal zone. LÄS MER

3. 17. Substrate control of community composition and functional adaptation in marine bacterioplankton

   Författare :Julie Dinasquet; Lasse Riemann; Edward F. DeLong; Linnéuniversitetet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; marine microbial ecology; bacterioplankton; community composition; functional adaptation; dissolved organic carbon; bottom-up and top down factors; ctenophore Mnemiopsis leidyi; food-webs; Southern-Ocean; Antarctica; Mikrobiologi; Microbiology; Akvatisk ekologi; Aquatic Ecology;

   Sammanfattning : A drop of sea-water is teeming with a million of bacteria, on which pelagic food-webs and biogeochemical cycles depend. These bacteria thrive on a wide range of dissolved organic carbon (DOC) compounds produced through biotic and abiotic processes. LÄS MER

4. 18. Summer cyanobacterial blooms in the Baltic Sea - implications for copepod recruitment

   Författare :Hedvig Hogfors; Sture Hansson; Wim Kimmerer; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Cyanobacteria; Calanoid copepods; Food web interactions; Harmful algae blooms; Zooplankton; Nodularin; Allelopathy; Baltic Sea; Biochemical markers; RNA-based indices; Acidification; Global Climate Change; Marine Ecology; marin ekologi;

   Sammanfattning : During summer, the Baltic Sea is subjected to the world’s largest cyanobacterial blooms. These blooms are linked to eutrophication and raise many questions concerning their effects on the ecosystem. To understand their impacts on the food web dynamics, it is essential to assess growth responses of grazers to these cyanobacteria. LÄS MER

5. 19. Top-down and bottom-up effects in a Fennoscandian tundra community

   Författare :Doris Grellmann; Lars Ericson; Lauri Oksanen; Richard Inouye; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; consumer-resource interactions; exclosures; food web dynamics; grey-sided voles; lemmings; NPK-fertilization; plant defences; reindeer; soil microbes; vertebrate grazing;

   Sammanfattning : The objective of this thesis was to investigate the effects of mammalian grazers, such as microtine rodents and reindeer, (top-down effects) and nutrient availability (bottom- up effects) on the plant community of a tundra heath.I conducted a large-scale fertilization experiment and studied the impact of grazers using exclosures. LÄS MER

7. 20. Ecosystem functioning in streams : Disentangling the roles of biodiversity, stoichiometry, and anthropogenic drivers

   Författare :André Frainer; Roland Jansson; Brendan McKie; Jonathan Benstead; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; detrital food web; functional diversity; stoichiometry; nitrogen and phosphorus concentrations; recalcitrant carbon; spatial and temporal species distribution; pools and riffles; isotopes; leaf decomposition rates; land use; restoration; habitat complexity;

   Sammanfattning : What will happen to ecosystems if species continue to go extinct at the high rates seen today? Although ecosystems are often threatened by a myriad of physical or chemical stressors, recent evidence has suggested that the loss of species may have impacts on the functions and services of ecosystems that equal or exceed other major environmental disturbances. The underlying causes that link species diversity to ecosystem functioning include species niche complementarity, facilitative interactions, or selection effects, which cause process rates to be enhanced in more diverse communities. LÄS MER