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Food quantity and quality regulation of trophic transfer between primary producers and a keystone grazer (Daphnia) in pelagic freshwater food webs
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.
2007 (English)In: Oikos, ISSN 0030-1299, E-ISSN 1600-0706, Vol. 116, no 7, 1152-1163 p.Article in journal (Refereed) Published
Abstract [en]

The transfer of energy and nutrients from plants to animals is a key process in all ecosystems. In lakes, inefficient transfer of primary producer derived energy can result in low animal growth rates, accumulation of nuisance phytoplankton blooms and dissipation of energy from the ecosystem. Most research on carbon transfer efficiency in pelagic food webs has focused on either food quantity or food quality, with the latter considered separately as either elemental stoichiometry or biochemical composition. The natural occurrence and magnitude of these types of growth limitations and their combined effects on Daphnia, a keystone grazer in pelagic freshwater ecosystems, are largely unknown. Our empirical models predict that the strength and nature of food quantity and quality limitation varies greatly with lake trophic state (total phosphorus, TP) and that Daphnia growth rates and thus energy and nutrient transfer efficiency are highest in lakes with intermediate trophic status (TP 10-25 μg l−1). We predict that food availability place the greatest constraint on Daphnia growth in nutrient poor lakes (TP≤4 μg l−1). Phosphorus limitation of Daphnia growth increased with decreasing TP, but the overall effect was never predicted to be the dominant constraining factor. Eicosapentaenoic acid (EPA, 20:5ω3) limitation was predicted to occur in both nutrient poor and nutrient rich lakes and placed the primary constraint on food quality in the most productive lakes. Two contrasting EPA-models gave different results on the magnitude of EPA-limitation, implying that additional food quality factors decrease Daphnia growth at high TP. In conclusion, the model predicts that Daphnia growth should peak in mesotrophic lakes, food quantity will place the greatest constraint on growth in oligotrophic lakes and EPA will primarily limit growth in eutrophic lakes.

Place, publisher, year, edition, pages
2007. Vol. 116, no 7, 1152-1163 p.
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-95736DOI: 10.1111/j.0030-1299.2007.15639.xISI: 000247438000007OAI: oai:DiVA.org:uu-95736DiVA: diva2:170061
Available from: 2007-04-11 Created: 2007-04-11 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Food Quality Effects on Zooplankton Growth and Energy Transfer in Pelagic Freshwater Food Webs
Open this publication in new window or tab >>Food Quality Effects on Zooplankton Growth and Energy Transfer in Pelagic Freshwater Food Webs
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Effekter av födokvalitet på djurplanktons tillväxt och på energiöverföringen i födovävar i sjöar
Abstract [en]

Poor food quality can have large negative effects on zooplankton growth and this can also affect food web interactions. The main aims of this thesis were to study the importance of different food quality aspects in Daphnia, to identify potentially important differences among zooplankton taxa, and to put food quality research into a natural context by identifying the importance of food quality and quantity in lakes of different nutrient content.

In the first experiment, the RNA:DNA ratio was positively related to the somatic growth rate of Daphnia, supporting a connection between P content, RNA content, and growth rate. The second experiment showed that EPA was important for Daphnia somatic growth, and 0.9 µg EPA mg C-1 was identified as the threshold below which negative effects on Daphnia growth occurred.

A field survey identified patterns in the PUFA content of zooplankton that could be explained by taxonomy and trophic position. Cladocera enriched EPA and ARA relative to seston, and Copepoda primarily enriched DHA. In a whole-lake experiment, gentle fertilization of an oligotrophicated reservoir increased the seston P content and the biomass of high quality phytoplankton (Cryptophyceae, high EPA content). This was followed by increases in zooplankton and fish biomasses.

An empirical model based on data from a literature survey predicted that food quantity is most important for zooplankton growth in oligotrophic lakes, and that food quality factors are more important in eutrophic lakes. Thus, zooplankton growth, and energy transfer efficiency in the food web, is predicted to be highest in mesotrophic lakes. The results predict that the strength and nature of food quantity and quality limitation of Daphnia growth varies with lake trophic state, and that some combination of food quantity and/or quality limitation should be expected in nearly all lakes.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 43 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 292
Keyword
Ecology, elemental stoichiometry, phosphorus, polyunsaturated fatty acids, EPA, oligotrophic lakes, empirical modelling, Daphnia, Cladocera, Copepoda, Ekologi
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-7811 (URN)978-91-554-6859-0 (ISBN)
Public defence
2007-05-04, Zootissalen, Gamla Zoologen, Norbyvägen 18, Uppsala, 10:00
Opponent
Supervisors
Available from: 2007-04-11 Created: 2007-04-11 Last updated: 2016-04-28Bibliographically approved

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