Sökning: "trophic position"

Visar resultat 1 - 5 av 14 avhandlingar innehållade orden trophic position.

1. 1. Dynamics of omnivorous crayfish in freshwater ecosystems

   Författare :Karin Olsson; Biologiska institutionen; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; crayfish; freshwater ecosystems; niche width; growth rate; stable isotope analysis; recruitment; RNA:DNA analysis; Ecology; food availability and quality; trophic position; population dynamics;

   Sammanfattning : In this thesis I examine the dynamics of crayfish in streams and lakes. I have studied the influence of abiotic and biotic factors on abundance, growth, trophic position, niche breadth, and recruitment of crayfish, by conducting field studies, an outdoor channel experiment and timeseries analysis. LÄS MER

3. 2. Towards understanding stable isotope signatures in stressed systems

   Författare :Caroline Ek; Elena Gorokhova; Katrine Borgå; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Stable isotope analysis; trophic position; chemical exposure; oxidative stress; Daphnia magna; Gammarus spp.; Limecola balthica; Applied Environmental Science; tillämpad miljövetenskap;

   Sammanfattning : Stable isotope analysis (SIA) is a valuable tool in ecotoxicology because δ13C and δ15N may provide insights into the trophic transfer of contaminants in a food web. The relationship between a species’ trophic position (TP, determined from δ15N) and internal concentration of biomagnifying contaminants can be established and used for regulatory purposes. LÄS MER

4. 3. Coping with environmental change : Lessons from isotope studies in a sentinel species

   Författare :Matias Ledesma; Agnes Karlson; Marleen De Troch; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; stable isotope; compound-specific nitrogen stable isotope analysis; trophic niche; harmful algae blooms; contaminants; stress; reproductive success; environmental change; Baltic Sea; marin ekologi; Marine Ecology;

   Sammanfattning : Adaptive evolution and phenotypic plasticity are two key mechanisms by which natural populations avoid extinction in the face of environmental change. Evolutionary young systems, such as the Baltic Sea with low species diversity and steep environmental gradients, are good models for studying how wild populations cope with environmental changes, such as climate-induced alterations in food supply and exposure to environmental contaminants. LÄS MER

5. 4. Non-indigenous zooplankton : the role of predatory cladocerans and of copepods in trophic dynamics

   Författare :Marc Andersen Borg; Fredrik Wulff; Markku Viitasalo; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Acartia tonsa; Bythotrephes longimanus; Cercopagis pengoi; egg production; fitness; food web changes; ingestion rates; invasive species; metabolic balance; mortality; non-indigenous zooplankton; predation impact; salinity tolerance; stable isotopes; Marine ecology; Marin ekologi; marin ekologi; Marine Ecology;

   Sammanfattning : Human-mediated introductions of non-indigenous species now threaten to homogenize the biota of the Globe, causing huge economic and ecological damage. This thesis studies the ecological role of 3 invasive planktonic crustaceans, the omnivorous copepod Acartia tonsa (western Atlantic and Indo-Pacific) and the predatory cladocerans, Cercopagis pengoi (Ponto-Caspian) and Bythotrephes longimanus (Eurasian). LÄS MER

7. 5. Species interactions and energy transfer in aquatic food webs

   Författare :Jens Munk Nielsen; Monika Winder; Sture Hansson; Michael T. Brett; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Aquatic food webs; zooplankton; stable isotope analysis amino acids; molecular diet analysis; Marine Ecology; marin ekologi;

   Sammanfattning : Food webs are structured by intricate nodes of species interactions which govern the flow of organic matter in natural systems. Despite being long recognized as a key component in ecology, estimation of food web functioning is still challenging due to the difficulty in accurately measuring species interactions within a food web. LÄS MER