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Experimental Studies on the Regulation of Pigment Dynamics in Phytoplankton and Copepods by Dissolved Inorganic Nutrients
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för evolution, genomik och systematik, Evolutionsbiologi.
2004 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis , 2004. , s. 34
Serie
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 968
Emneord [en]
Biology, Astaxanthin, Baltic Sea, carotenoids, diatoms, eutrophication, food web, mesocosms, microalgae, M74 syndrome, oxidative stress, phytoplankton blooms, zooplankton
Emneord [sv]
Biologi
HSV kategori
Identifikatorer
URN: urn:nbn:se:uu:diva-4230ISBN: 91-554-5946-3 (tryckt)OAI: oai:DiVA.org:uu-4230DiVA, id: diva2:164468
Disputas
2004-05-26, The lecture hall, Dept. of Plant Ecology, Villavägen 14, Uppsala, 10:00
Opponent
Veileder
Tilgjengelig fra: 2004-04-26 Laget: 2004-04-26 Sist oppdatert: 2011-03-04bibliografisk kontrollert
Delarbeid
1. Density-dependent patters of thiamine and pigment production in the diatom Nitzschia microcephala
Åpne denne publikasjonen i ny fane eller vindu >>Density-dependent patters of thiamine and pigment production in the diatom Nitzschia microcephala
Vise andre…
2003 Inngår i: Phytochemistry, Vol. 63, nr 2, s. 155-163Artikkel i tidsskrift (Fagfellevurdert) Published
Identifikatorer
urn:nbn:se:uu:diva-91657 (URN)
Tilgjengelig fra: 2004-04-26 Laget: 2004-04-26bibliografisk kontrollert
2. Astaxanthin levels in copepods depend on microalgal diet
Åpne denne publikasjonen i ny fane eller vindu >>Astaxanthin levels in copepods depend on microalgal diet
Artikkel i tidsskrift (Fagfellevurdert) Submitted
Identifikatorer
urn:nbn:se:uu:diva-91658 (URN)
Tilgjengelig fra: 2004-04-26 Laget: 2004-04-26bibliografisk kontrollert
3. Pigment transfer from phytoplankton to zooplankton with emphasis on astaxanthin production in the Baltic Sea food web
Åpne denne publikasjonen i ny fane eller vindu >>Pigment transfer from phytoplankton to zooplankton with emphasis on astaxanthin production in the Baltic Sea food web
2003 Inngår i: Marine Ecology Progress Series, Vol. 254, s. 312-224Artikkel i tidsskrift (Fagfellevurdert) Published
Identifikatorer
urn:nbn:se:uu:diva-91659 (URN)
Tilgjengelig fra: 2004-04-26 Laget: 2004-04-26bibliografisk kontrollert
4. Growth and C:N:P ratios in copepods grazing on N- or Si-limited phytoplankton blooms
Åpne denne publikasjonen i ny fane eller vindu >>Growth and C:N:P ratios in copepods grazing on N- or Si-limited phytoplankton blooms
2004 (engelsk)Inngår i: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 514, nr 1-3, s. 57-72Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The aim of this study was to investigate how nutrient limitation in phytoplankton blooms affects growth and C:N:Pratios in marine pelagic copepods.We performed two mesocosm experiments on the Atlantic coast near Trondhjem(Norway). Si-limitation in a phytoplankton bloom was triggered by N and P additions (NP treatment) and Nlimitationwas triggered by N, P and Si additions (NPSi treatment). Both nutrient treatments stimulated microalgalgrowth and increased the biomass of the phytoplankton manifold. The initial phytoplankton community consistedof flagellates and diatoms. Throughout both experiments, community composition stayed relatively stable anddiverse in the NP treatments, but in the NPSi treatments large and heavily silicified diatoms came to dominatecompletely. Phytoplankton C:N ratios in the Si-limited blooms were close to the Redfield ratio of 6.6 (on a molarbasis), but they were higher in the Control treatment without nutrient additions (ca. 8.6) and up to 14 in heavily Nlimitedblooms. When phytoplankton blooms (chlorophyll a > 25 nmol l−1) had established, wild copepods wereadded to the mesocosms. During Si-limitation the copepod density increased by ca. 40% in one of the experiments,while the C:N ratio was 5.5–6 in the copepods. During N-limitation, the copepod density stayed stable, while theC:N ratio increased to ca. 7 in the course of the experiment. In the other experiment the copepod density decreasedby ca. 25%, irrespective of nutrient treatment (C:N ratio ca. 9). The N:P ratios in the copepods varied between 16and 22 and were not different in the NP and NPSi treatments. Our study shows that N-limitation in phytoplanktoncells can increase the C:N ratio of their grazers, which has a reportedly negative effect on copepod growth andreproduction. Our study also shows that copepod populations can be regulated by seawater Si:N ratios via diatoms:at high ratios the growth from eggs/nauplii to copepodites was hampered. High Si:N ratios provide diatoms withpossibilities to escape from grazing (large species, heavy silicification, excretion of secondary metabolites), leadingto the accumulation of algal biomass without transfer to higher trophic levels.

Emneord
nutrient limitation, silicate, nitrogen, phosphorus, copepods, phytoplankton, mesocosm experiments
HSV kategori
Identifikatorer
urn:nbn:se:uu:diva-91660 (URN)10.1023/B:hydr.0000018206.02271.2b (DOI)
Tilgjengelig fra: 2004-04-26 Laget: 2004-04-26 Sist oppdatert: 2017-12-14bibliografisk kontrollert
5. Astaxanthin levels in marine pelagic copepods grazing on two different phytoplankton diets
Åpne denne publikasjonen i ny fane eller vindu >>Astaxanthin levels in marine pelagic copepods grazing on two different phytoplankton diets
Artikkel i tidsskrift (Fagfellevurdert) Submitted
Identifikatorer
urn:nbn:se:uu:diva-91661 (URN)
Tilgjengelig fra: 2004-04-26 Laget: 2004-04-26bibliografisk kontrollert
6. Pigments dynamics in phytoplankton and copepods can be manipulated by inorganic nutrients
Åpne denne publikasjonen i ny fane eller vindu >>Pigments dynamics in phytoplankton and copepods can be manipulated by inorganic nutrients
Manuskript (Annet vitenskapelig)
Identifikatorer
urn:nbn:se:uu:diva-91662 (URN)
Tilgjengelig fra: 2004-04-26 Laget: 2004-04-26 Sist oppdatert: 2010-01-13bibliografisk kontrollert

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