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Density-dependent patters of thiamine and pigment production in the diatom Nitzschia microcephala
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology, Evolutionary Biology.
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2003 In: Phytochemistry, Vol. 63, no 2, 155-163 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2003. Vol. 63, no 2, 155-163 p.
URN: urn:nbn:se:uu:diva-91657OAI: oai:DiVA.org:uu-91657DiVA: diva2:164462
Available from: 2004-04-26 Created: 2004-04-26Bibliographically approved
In thesis
1. Experimental Studies on the Regulation of Pigment Dynamics in Phytoplankton and Copepods by Dissolved Inorganic Nutrients
Open this publication in new window or tab >>Experimental Studies on the Regulation of Pigment Dynamics in Phytoplankton and Copepods by Dissolved Inorganic Nutrients
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis examines the role of dissolved inorganic nutrients in generating changes in phytoplankton community and pigment composition and if such changes can affect the production of the antioxidant astaxanthin in the ecosystem via pelagic copepods. The background of my studies is the possible relationship between eutrophication and a reproductive disturbance in Baltic populations of Atlantic salmon (M74), which is associated with astaxanthin and thiamine deficiencies and oxidative stress. In the southern Baltic Sea, changes in nutrient loads correlate with observed trends of flagellates replacing diatoms in the phytoplankton. Copepods are the main producers of astaxanthin and a major link between phytoplankton and higher trophic levels. In laboratory and field experiments in the Baltic Sea proper and the Norwegian Sea, I show that astaxanthin synthesis in copepods is fast and depends on pigment composition of the phytoplankton diet. Among single-species diets, a diatom and a green algal cyst yielded the highest astaxanthin levels in copepods, and another diatom species, a green alga and a cyanobacterium the lowest. In nutrient-generated phytoplankton blooms in mesocosms, copepods grazing on diverse communities dominated by weakly silicified diatoms produced more astaxanthin compared with copepods grazing on communities dominated by strongly silicified diatoms. This suggests that diatoms invested in defence mechanisms and escaped grazing at surplus Si. A nutrient-starved diatom culture subjected to intraspecific competition exhibited decreased pigment levels, increased thiamine levels and increased oxidative stress.

My results suggest that diatoms are beneficial for astaxanthin and thiamine production compared to other phytoplankton groups, but not under all circumstances. Copepod growth and development also responded to inorganic nutrient availability and affected total astaxanthin production per volume seawater, with highest production when the copepods grazed on diatoms. From an ecosystem perspective, increased N and P loads seem to promote high astaxanthin production, but not when diatoms disappear completely.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 34 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 968
Biology, Astaxanthin, Baltic Sea, carotenoids, diatoms, eutrophication, food web, mesocosms, microalgae, M74 syndrome, oxidative stress, phytoplankton blooms, zooplankton, Biologi
National Category
Biological Sciences
urn:nbn:se:uu:diva-4230 (URN)91-554-5946-3 (ISBN)
Public defence
2004-05-26, The lecture hall, Dept. of Plant Ecology, Villavägen 14, Uppsala, 10:00
Available from: 2004-04-26 Created: 2004-04-26 Last updated: 2011-03-04Bibliographically approved

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