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Vrede, Tobias
Alternative names
Publications (10 of 11) Show all publications
Vrede, T. & Tranvik, L. (2006). Iron constraints on planktonic primary production in oligotrophic lakes. Ecosystems (New York. Print), 9(7), 1094-1105
Open this publication in new window or tab >>Iron constraints on planktonic primary production in oligotrophic lakes
2006 (English)In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, Vol. 9, no 7, p. 1094-1105Article in journal (Refereed) Published
Abstract [en]

Phototrophic primary production is a fundamental ecosystem process, and it is ultimately constrained by access to limiting nutrients. Whereas most research on nutrient limitation of lacustrine phytoplankton has focused on phosphorus (P) and nitrogen (N) limitation, there is growing evidence that iron (Fe) limitation may be more common than previously acknowledged. Here we show that P was the nutrient that stimulated phytoplankton primary production most strongly in seven out of nine bioassay experiments with natural lake water from oligotrophic clearwater lakes. However, Fe put constraints on phytoplankton production in eight lakes. In one of these lakes, Fe was the nutrient that stimulated primary production most, and concurrent P and Fe limitation was observed in seven lakes. The effect of Fe addition increased with decreasing lake water concentrations of total phosphorus and dissolved organic matter. Possible mechanisms are low import rates and low bioavailability of Fe in the absence of organic chelators. The experimental results were used to predict the relative strength of Fe, N, and P limitation in 659 oligotrophic clearwater lakes (with total phosphorus <= 0.2 mu M P and total organic carbon < 6 mg C l(-1)) from a national lake survey. Fe was predicted to have a positive effect in 88% of these lakes, and to be the nutrient with the strongest effect in 30% of the lakes. In conclusion, Fe, along with P and N, is an important factor constraining primary production in oligotrophic clearwater lakes, which is a common lake-type throughout the northern biomes.

Keywords
phytoplankton, primary production, nutrient limitation, micronutrients, oligotrophic clearwater lakes
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-23165 (URN)10.1007/s10021-006-0167-1 (DOI)000242334600005 ()
Available from: 2007-05-24 Created: 2007-05-24 Last updated: 2017-12-07Bibliographically approved
Persson, J. & Vrede, T. (2006). Polyunsaturated fatty acids in zooplankton: variation due to taxonomy and trophic position. Freshwater Biology, 51, 887-900
Open this publication in new window or tab >>Polyunsaturated fatty acids in zooplankton: variation due to taxonomy and trophic position
2006 (English)In: Freshwater Biology, Vol. 51, p. 887-900Article in journal (Refereed) Published
Abstract [en]

1. Food quality has major effects on the transfer of energy and matter in food webs, and

essential long-chained polyunsaturated fatty acids (PUFAs) can affect the quality of

phytoplankton as food. In a study of oligotrophic lakes in north-western Sweden, we

investigated the fatty acid composition of four planktonic cladocerans and two calanoid

copepods, representing herbivorous and carnivorous species. We also collected seston

samples.

2. The proportions of long-chain PUFAs in the organisms increased with their increasing

trophic position. Thus, both their quality as food for other organisms, as well as their

requirement for fatty acids (FAs), differed among taxa and depended on their trophic

position.

3. We found taxon-specific differences in the FA composition of zooplankton that were not

related to sestonic FA composition. This implies that the variation in zooplankton FA

composition is constrained by phylogenetic origin, life history characteristics, or both.

4. The cladoceran taxa contained 12–23% eicosapentaenoic acid (EPA) but only 0.9–2.1%

docosahexaenoic acid (DHA) of the total FA content. In contrast, the calanoid copepods

contained 7–11% EPA and 14–21% DHA. Thus, our results show that differences in the

PUFA content among zooplankton species could have repercussions for both food web

structure and function.

Keywords
Cladocera, Copepoda, docosahexaenoic acid, eicosapentaenoic acid, food quality
Identifiers
urn:nbn:se:uu:diva-23200 (URN)
Available from: 2007-01-25 Created: 2007-01-25 Last updated: 2011-01-11
Vrede, T., Rydin, E. & Milbrink, G. (2006). Restoration of fish stocks in oligotrophicated regulated reservoirs. Dams under Debate
Open this publication in new window or tab >>Restoration of fish stocks in oligotrophicated regulated reservoirs
2006 (English)In: Dams under DebateArticle in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-23176 (URN)
Available from: 2007-05-24 Created: 2007-05-24 Last updated: 2011-01-11
Vrede, T. & Vrede, K. (2005). Contrasting “top-down” effects of crustacean zooplankton grazing on bacteria and phytoflagellates. Aquatic Ecology, 39, 283-293
Open this publication in new window or tab >>Contrasting “top-down” effects of crustacean zooplankton grazing on bacteria and phytoflagellates
2005 (English)In: Aquatic Ecology, Vol. 39, p. 283-293Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-76823 (URN)
Available from: 2006-04-19 Created: 2006-04-19 Last updated: 2011-01-11
Vrede, T., Dobberfuhl, D. R., Kooijman, S. A. & Elser, J. J. (2004). FUNDAMENTAL CONNECTIONS AMONG ORGANISM C:N:P STOICHIOMETRY, MACROMOLECULAR COMPOSITION, AND GROWTH. Ecology, 85(5), 1217–1229
Open this publication in new window or tab >>FUNDAMENTAL CONNECTIONS AMONG ORGANISM C:N:P STOICHIOMETRY, MACROMOLECULAR COMPOSITION, AND GROWTH
2004 (English)In: Ecology, Vol. 85, no 5, p. 1217–1229-Article in journal (Refereed) Published
Abstract [en]

Whereas it is acknowledged that the C:N:P stoichiometry of consumers and their resources affects both the structure and the function of food webs, and eventually influences broad-scale processes such as global carbon cycles, the mechanistic basis for the variation in stoichiometry has not yet been fully explored. Empirical evidence shows that the specific growth rate is positively related to RNA concentration both between and within taxa in both unicellular and multicellular organisms. Since RNA is rich in P and constitutes a substantial part of the total P in organisms, a high growth rate is also connected with a high P content. We argue that the reason for this pattern is that the growth of all biota is closely linked with their protein synthesis rate, and thus with the concentration of ribosomal RNA. Dynamic energy budget theory supports the positive relationship between RNA and specific growth rate in microorganisms, whereas the predictions concerning multicellulars only partially agrees with the observed pattern. In a simple model of consumer growth, we explore the consequences of various allocation patterns of RNA, protein, carbohydrates/lipids, and other biochemical constituents on organism potential growth rate and C:N:P stoichiometry. According to the model the percentage of N and especially percentage of P per dry mass increases with increasing specific growth rate. Furthermore, the model suggests that macromolecule allocation patterns and thus N:P stoichiometry are allowed to differ substantially at low growth rates whereas the stoichiometry at high growth rates is much more constricted at low N:P. The model fits empirical data reasonably well, but it is also acknowledged that complex life cycles and associated physiological constraints may result in other patterns. We also use a similar approach of modeling organism growth from basic biochemical principles to illustrate fundamental connections among biochemical allocation and C:N stoichiometry in autotroph production, which is based on allocation patterns between carbohydrates and rubisco. Similar to the RNA–protein model, macromolecular composition and C:N ratios are more constrained at high than at low growth rates. The models and the empirical data together suggest that organism growth is tightly linked with the organisms' biochemical and elemental composition. The stoichiometry of growth impinges on nutrient cycles and carbon fluxes at the ecosystem level. Thus, focus on the biological basis of organism C:N:P stoichiometry can mechanistically connect growth strategy and biochemical and cellular mechanisms of biota to major ecological consequences.

Keywords
autotroph production; C:N:P stoichiometry; consumer growth rate; dynamic energy budget theory; macromolecular allocation patterns; protein allocation; ribosomal RNA; rubisco.
Identifiers
urn:nbn:se:uu:diva-72444 (URN)
Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2011-01-12
Loiterton, B., Sundbom, M. & Vrede, T. (2004). Separating physical and physiological effects of temperature on zooplankton feeding rate. Aquatic Sciences, 66, 123-129
Open this publication in new window or tab >>Separating physical and physiological effects of temperature on zooplankton feeding rate
2004 (English)In: Aquatic Sciences, Vol. 66, p. 123-129Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-72426 (URN)
Available from: 2008-04-14 Created: 2008-04-14 Last updated: 2011-01-12
Vrede, T., Persson, J. & Aronsen, G. (2002). The influence of food quality (P:C ratio) on RNA:DNA ratio and somatic growth rate of Daphnia. Limnology & Oceanography, 47(2), 487-494
Open this publication in new window or tab >>The influence of food quality (P:C ratio) on RNA:DNA ratio and somatic growth rate of Daphnia
2002 (English)In: Limnology & Oceanography, Vol. 47, no 2, p. 487-494Article in journal (Refereed) Published
Abstract [en]

Growth experiments with juvenile Daphnia galeata were

Identifiers
urn:nbn:se:uu:diva-42192 (URN)
Available from: 2006-04-19 Created: 2006-04-19 Last updated: 2011-01-13
Ahlgren, G., Hyenstrand, P., Vrede, T., Karlsson, E. & Zetterberg, S. (2001). Nutritional quality of Scenedesmus quadricauda (Chlorophyceae) grown in different nitrogen regimes and tested on Daphnia. International Association of Theoretical and Applied Limnology, 27(3), 1234-1238
Open this publication in new window or tab >>Nutritional quality of Scenedesmus quadricauda (Chlorophyceae) grown in different nitrogen regimes and tested on Daphnia
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2001 (English)In: International Association of Theoretical and Applied Limnology, Vol. 27, no 3, p. 1234-1238Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-36181 (URN)
Available from: 2007-01-25 Created: 2007-01-25 Last updated: 2011-01-13
Vrede, T., Andersen, T. & Hessen, D. O. (1999). Phosphorus distribution in three crustacean zooplankton species. LIMNOLOGY AND OCEANOGRAPHY, 44(1), 225-229
Open this publication in new window or tab >>Phosphorus distribution in three crustacean zooplankton species
1999 (English)In: LIMNOLOGY AND OCEANOGRAPHY, ISSN 0024-3590, Vol. 44, no 1, p. 225-229Article in journal (Refereed) Published
Abstract [en]

The distribution of phosphorus (P) was assessed in homogeneously P-33-labeled Daphnia magna, Daphnia galeata and Eudiaptomus gracilis. The specific P contents were 1.48, 1.41, and 0.50% of dry weight (DW), respectively. The results support the view of low

Keywords
GROWTH-RATE; DAPHNIA; LIMITATION; NITROGEN; CARBON; SIZE; RNA
Identifiers
urn:nbn:se:uu:diva-85039 (URN)
Note
Addresses: Vrede T, Uppsala Univ, Dept Limnol, Norbyvagen 20, SE-75236 Uppsala, Sweden. Uppsala Univ, Dept Limnol, SE-75236 Uppsala, Sweden. Univ Oslo, Dept Biol, Div Limnol, N-0315 Oslo, Norway.Available from: 2007-01-25 Created: 2007-01-25 Last updated: 2011-01-14
Vrede, T. (1998). Elemental composition (C : N : P) and growth rates of bacteria and Rhodomonas grazed by Daphnia. JOURNAL OF PLANKTON RESEARCH, 20(3), 455-470
Open this publication in new window or tab >>Elemental composition (C : N : P) and growth rates of bacteria and Rhodomonas grazed by Daphnia
1998 (English)In: JOURNAL OF PLANKTON RESEARCH, ISSN 0142-7873, Vol. 20, no 3, p. 455-470Article in journal (Refereed) Published
Abstract [en]

The elemental composition and growth rate of Rhodomonas and heterotrophic bacteria were studied in batch cultures in the presence and absence of Daphnia and at two different levels of phosphorus limitation. The elemental content of single cells was measur

Keywords
FRESH-WATER; BACTERIOPLANKTON GROWTH; NUTRIENT REGENERATION; MICROBIAL LOOP; PHOSPHORUS; ZOOPLANKTON; NITROGEN; LIMITATION; CARBON; PHYTOPLANKTON
Identifiers
urn:nbn:se:uu:diva-85053 (URN)
Note
Addresses: Vrede T, Univ Bergen, Dept Microbiol, Jahnebakken 5, N-5020 Bergen, Norway. Univ Uppsala, Inst Limnol, S-75122 Uppsala, Sweden.Available from: 2007-01-25 Created: 2007-01-25 Last updated: 2011-01-14
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