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Food web complexity affects stoichiometric and trophic interactions
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
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2006 (English)In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 114, no 1, 117-125 p.Article in journal (Refereed) Published
Abstract [en]

The stoichiometry of trophic interactions has mainly been studied in simple consumer–prey systems, whereas natural systems often harbour complex food webs with abundant indirect effects. We manipulated the complexity of trophic interactions by using simple laboratory food webs and complex field food webs in enclosures in Lake Erken. In the simple food web, one producer assemblage (periphyton) and its consumers (benthic snails) were amended by perch, which was externally fed by fish food. In the complex food web, two producer assemblages (periphyton and phytoplankton), their consumers (benthic invertebrates and zooplankton) and perch feeding on zooplankton were included. In the simple food web perch affected the stoichiometry of periphyton and increased periphyton biomass and the concentration of dissolved inorganic nitrogen. Grazers reduced periphyton biomass but increased its nutrient content. In the complex food web, in contrast to the simple food web, perch affected periphyton biomass negatively but increased phytoplankton abundance. Perch had no influence on benthic invertebrate density, zooplankton biomass or periphyton stoichiometry. Benthic grazers reduced periphyton biomass and nutrient content. The difference between the simple and the complex food web was presumably due to the increase of pelagic cyanobacteria (Gloeotrichia sp.) with fish presence in the complex food web, thus fish had indirect negative effects on periphyton biomass through nutrient competition and shading by cyanobacteria. We conclude that the higher food web complexity through the presence of pelagic primary producers (in this case Gloeotrichia sp.) influences the direction and strength of trophic and stoichiometric interactions.

Place, publisher, year, edition, pages
2006. Vol. 114, no 1, 117-125 p.
National Category
Ecology
Identifiers
URN: urn:nbn:se:uu:diva-94627DOI: 10.1111/j.2006.0030-1299.14517.xISI: 000239563300012OAI: oai:DiVA.org:uu-94627DiVA: diva2:168533
Available from: 2010-11-11 Created: 2006-05-24 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Nutrient Stoichiometry in Benthic Food Webs – Interactions Between Algae, Herbivores and Fish
Open this publication in new window or tab >>Nutrient Stoichiometry in Benthic Food Webs – Interactions Between Algae, Herbivores and Fish
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis was to identify general structuring mechanisms in benthic food webs within the framework of ecological stoichiometry theory. Ecological stoichiometry is defined as the balance of multiple chemical substances in ecological interactions and explicitly considers the combined dynamics of key elements such as carbon (C), nitrogen (N) and phosphorus (P). Ecological stoichiometry theory was developed for pelagic environments, thus it must be tested whether the same mechanisms are applicable to benthic environments.

In this thesis, ecological stoichiometry theory was used as a framework to investigate nutrient pathways in benthic littoral ecosystems. I conducted one invertebrate field sampling and six experiments. In the experiments, factors such as grazing, light, nutrients and fish presence were manipulated.

The results showed that stoichiometric variability in consumers could mostly be explained by taxa. However, there was some stoichiometric variability due to sampling season, site, and nutrient enrichment.

Grazing mostly increased periphyton N and P content, although nutrient recycling effects were dependent on grazer stoichiometry. Grazing changed benthic algal community composition by increasing the proportion of grazing resistant algae species. Additionally, grazing decreased algal diversity, especially under nutrient poor conditions. The manipulation of fish presence revealed that fish affected primary producer biomass and stoichiometry through nutrient recycling.

The manipulation of abiotic factors, such as light and nutrient addition could affect periphyton nutrient content, biomass and benthic algal chlorophyll a content. The separate addition of N or P led to an increase of the added nutrient in the periphyton. Increased light intensities led to a decreased cellular chlorophyll a content and increased C:nutrient ratios.

This thesis arrives at the conclusion that periphyton-grazer-predator interactions in the benthic are bound by stoichiometric constraints. Nutrient recycling by benthic invertebrates and fish are important mechanism in benthic littoral ecosystems.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 44 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 197
Keyword
Ecology, ecologial stoichiometry, periphyton, grazer, benthos, trophic interactions, nutrient, algae, Ekologi
Identifiers
urn:nbn:se:uu:diva-6933 (URN)91-554-6592-7 (ISBN)
Public defence
2006-09-08, Friessalen, Kärnhuset, EBC, Norbyvägen 18, 752 36 Uppsala, 10:00
Opponent
Supervisors
Available from: 2006-05-24 Created: 2006-05-24 Last updated: 2011-06-28Bibliographically approved

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Eklöv, Peter

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