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Prey diversity and prey stomach contents affect astaxanthin levels in piscivorous fish
Department of Ecology, Jian University, Guangzhou, China.
Department of Systems Ecology, Stockholm University.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Ecological Botany.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal Ecology.
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(English)In: Limnology and Oceanography, ISSN 0024-3590Article in journal (Refereed) Submitted
Abstract [en]

We analyzed astaxanthin concentrations and the composition of geometrical (E/Z) astaxanthin isomers in 631 tissue samples from the four chief fish species in the pelagic zone of the brackish Baltic Sea. Salmon and herring showed signs of astaxanthin deficiency, but cod and sprat did not. The isomers were distributed selectively in fish tissues, with highest proportions of all-E-astaxanthin in salmon gonads (71%) and lowest in herring gonads (19%). We discovered that the clupeids are no ideal prey for salmon and cod with respect to their high whole-body concentrations of astaxanthin Z-isomers, which have low bioavailability for salmon and cod. The salmon in the Baltic Sea is entirely dependent on herring and sprat for food intake while cod feeds on a more diverse diet, including crustaceans. This explains the normal low astaxanthin levels in the salmon in the Baltic Sea. Observed decreases in astaxanthin levels in the Baltic salmon during the last 50 years, which are related to a reproductional disturbance (M74 syndrome), can be explained by the here described poor quality of herring as astaxanthin source in combination with recorded changes in the feeding ecology of the Baltic salmon with less sprat and more herring in the diet today. Herring is inferior to sprat as astaxanthin source, especially in autumn when a salmon or cod obtains four times more bioavailable all-E-astaxanthin (by weight) from sprat than from herring. The Baltic herring is starving more than the sprat as a result of competition between the clupeids though fishing mortality and recruitment problems of the cod, their major predator during the last decades. Therefore, less crustacean astaxanthin (mainly all-E) is transferred directly to piscivorous fish from herring stomachs than from sprat stomachs.

Keyword [en]
Baltic Sea, cod, food web, herring, pelagic, regime shift, salmon, sprat
URN: urn:nbn:se:uu:diva-130142OAI: oai:DiVA.org:uu-130142DiVA: diva2:346645
Available from: 2010-09-02 Created: 2010-09-02 Last updated: 2011-01-10Bibliographically approved
In thesis
1. Dynamics of astaxanthin, tocopherol (Vitamin E) and thiamine (Vitamin B1) in the Baltic Sea ecosystem: Bottom-up effects in an aquatic food web
Open this publication in new window or tab >>Dynamics of astaxanthin, tocopherol (Vitamin E) and thiamine (Vitamin B1) in the Baltic Sea ecosystem: Bottom-up effects in an aquatic food web
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The thesis combines laboratory experiments and field expeditions to study production, transfer and consumption of non-enzymatic antioxidants and thiamine in an aquatic food web. In particular, I (1) documented spatial and seasonal variation of tocopherols and carotenoids in the Baltic Sea pelagic food web, and (2) examined the effects of abiotic and biotic factors on tocopherol, carotenoid and thiamine concentrations in phytoplankton, zooplankton and fish.

Moderate differences in temperature and salinity affected α-tocopherol, β-carotene and thiamine production in microalgae. Furthermore, the results suggest that acute stress favors the expression of non-enzymatic antioxidants rather than enzymatic antioxidants. Because production of α-tocopherol, β-carotene and thiamine differ markedly between microalgae, the availability of non-enzymatic antioxidants and thiamine is likely to be highly variable in the Baltic Sea and is difficult to predict.

The transfer of non-enzymatic antioxidants from phytoplankton to zooplankton was biomass dependent. The field expeditions revealed that phytoplankton biomass was negatively associated with α-tocopherol concentration in mesozooplankton. Thus, increased eutrophication of the Baltic Sea followed by an increase in phytoplankton biomass could decrease the transfer of essential biochemicals to higher levels in the pelagic food web. This could lead to deficiency syndromes, of the kind already observed in the Baltic Sea. Astaxanthin is synthesized from precursors provided by the phytoplankton community. Thus biomass dependent transfer of astaxanthin precursors from phytoplankton to zooplankton could be responsible for astaxanthin deficiency in zooplanktivorous herring. Astaxanthin in herring consists mostly of all-Z-isomers, which are characterized by low bioavailability. Therefore, astaxanthin deficiency in salmon could be explained by the low concentration of this substance and its isomeric composition in herring.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 47 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 762
Baltic Sea, carotenoids, astaxanthin, tocopherols, Vitamin E, thiamine, Vitamin B1, pelagic food web, eutrophication, M74, phytoplankton, zooplankton, sprat, Sprattus sprattus balticus, herring, Clupea harengus, salmon, Salmo salar, cod, Gadus morhua, High Performance Liquid Chromatography (HPLC), electrochemical detection (ECD)
urn:nbn:se:uu:diva-130143 (URN)978-91-554-7878-0 (ISBN)
Public defence
2010-10-15, Lindahlsalen, Norbyvägen 18, EBC, Uppsala, 10:00 (English)
Available from: 2010-09-23 Created: 2010-09-02 Last updated: 2011-01-10

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