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| 6. |
- Gylle, A Maria, 1965-
(författare)
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Physiological adaptations in two ecotypes of Fucus vesiculosus and in Fucus radicans with focus on salinity
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The in origin intertidal marine brown alga Fucus vesiculosus L. grow permanently sublittoral in the brackish Bothnian Sea, side by side with the recently discovered F. radicans L. Bergström et L. Kautsky. Environmental conditions like salinity, light and temperature are clearly different between F. vesiculosus growth sites in the Bothnian Sea (4-5 practical salinity units, psu; part of the Baltic Sea) and the tidal Norwegian Sea (34-35 psu; part of the Atlantic Ocean). The general aims of this thesis were to compare physiological aspects between the marine ecotype and the brackish ecotype of F. vesiculosus as well as between the two Bothnian Sea species F. vesiculosus and F. radicans.The result in the study indicates a higher number of water soluble organic compounds in the marine ecotype of F. vesiculosus compared to the brackish ecotype. These compounds are suggested to be compatible solutes and be due to an intertidal and sublittoral adaptation, respectively; where the intertidal ecotype needs the compounds as a protection from oxygen radicals produced during high irradiation at low tide. The sublittoral ecotype might have lost the ability to synthesize these compound/compounds due to its habitat adaptation. The mannitol content is also higher in the marine ecotype compared to the brackish ecotype of F. vesiculosus and this is suggested to be due to both higher level of irradiance and higher salinity at the growth site.77 K fluorescence emission spectra and immunoblotting of D1 and PsaA proteins indicate that both ecotypes of F. vesiculosus as well as F. radicans have an uneven ratio of photosystem II/photosystem I (PSII/PSI) with an overweight of PSI. The fluorescence emission spectrum of the Bothnian Sea ecotype of F. vesiculosus however, indicates a larger light-harvesting antenna of PSII compared to the marine ecotype of F. vesiculosus and F. radicans. Distinct differences in 77 K fluorescence emission spectra between the Bothnian Sea ecotype of F. vesiculosus and F. radicans confirm that this is a reliable method to use to separate these species.The marine ecotype of F. vesiculosus has a higher photosynthetic maximum (Pmax) compared to the brackish ecotype of F. vesiculosus and F. radicans whereas both the brackish species have similar Pmax. A reason for higher Pmax in the marine ecotype of F. vesiculosus compared to F. radicans is the greater relative amount of ribulose-1.5-bisphosphate carboxylase/oxygenase (Rubisco). The reason for higher Pmax in marine ecotype of F. vesiculosus compare to the brackish ecotype however is not due to the relative amount of Rubisco and further studies of the rate of CO2 fixation by Rubisco is recommended. Treatments of the brackish ecotype of F. vesiculosus in higher salinity than the Bothnian Sea natural water indicate that the most favourable salinity for high Pmax is 10 psu, followed by 20 psu. One part of the explanation to a high Pmax in 10 psu is a greater relative amount of PsaA protein in algae treated in 10 psu. The reason for greater amount of PsaA might be that the algae need to produce more ATP, and are able to have a higher flow of cyclic electron transport around PSI to serve a higher rate of CO2 fixation by Rubisco. However, studies of the rate of CO2 fixation by Rubisco in algae treated in similar salinities as in present study are recommended to confirm this theory.
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| 7. |
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| 8. |
- Häubner, Norbert
(författare)
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Dynamics of astaxanthin, tocopherol (Vitamin E) and thiamine (Vitamin B1) in the Baltic Sea ecosystem : Bottom-up effects in an aquatic food web
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 9. |
- Häubner, Norbert, et al.
(författare)
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Phytoplankton biomass controls tocopherol concentrations in Baltic Sea zooplankton
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Ingår i: Marine Ecology Progress Series. - 0171-8630 .- 1616-1599.
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Tidskriftsartikel (refereegranskat)abstract
- Nearly all organisms are constantly exposed to oxidative threat, because every reaction where oxygen is involved gives rise to oxidants. Efficient protection is provided by antioxidants. Vitamin E (tocopherol) is an essential plant-derived antioxidant and poorly studied so far in marine food webs. In 2004 and 2005 eight offshore expeditions were conducted in the Baltic Sea to explore the dynamics of α-tocopherol in the pelagic food web. In order to analyze tocopherol production and transition to the next food web level, two plankton size classes were sampled; <100 µm (dominated by phytoplankton) and >200 µm (dominated by calanoid copepods). HPLC analysis revealed lowest values of α-tocopherol per L seawater in March in both size classes and highest in May for <100 µm (31.5 ng L-1) and August for >200 µm (1.3 ng L-1). No consistent seasonal pattern could be observed in α-tocopherol per unit biomass for the zooplankton. Concentrations ranged in <100 µm from 0.05 to 0.10 ng µg C-1 and in >200 µm from 0.05 to 0.11 ng µg C-1. Partial least square regression (PLS) revealed nutrional status and species composition of the phytoplankton biomass as driving factors of α-tocopherol production in phytoplankton. Abiotic factors, as depth and temperature were only of significant influence in May. In zooplankton, the α-tocopherol concentration was negatively associated with phytoplankton biomass in May. Therefore we concluded that assimilation efficiency of zooplankton in combination with high phytoplankton biomass is the bottle-neck in tocopherol transport from phytoplankton to higher levels in the food web.
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| 10. |
- Häubner, Norbert, et al.
(författare)
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Response of alpha-tocopherol and beta-carotene production in microalgae to temperature, salinity and photon flux density
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Ingår i: Journal of Applied Phycology. - 0921-8971 .- 1573-5176.
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Tidskriftsartikel (refereegranskat)abstract
- Oxidative stress occurs in plant and animal cells in association with oxygen. Therefore non-enzymatic antioxidants, like α-tocopherol and β-carotene, are necessary in to prevent irreversible damages caused by reactive oxygen species. Most antioxidants or their precursors are plant-derived and any fluctuation in the synthesis of these substances will affect consumers directly. To study the effects of environmental factors on antioxidant production by microalgae, cultures of the microalgae Dunaliella tertiolecta (Chlorophyceae), Nodularia spumigena (Cyanophyceae), Prorocentrum minimum Dinophyceae), Phaeodactylum tricornutum (Bacillariophyceae) , Skeletonema costatum (Mediophyceae) and Rhodomonas salina (Cryptophyceae) were incubated for 48 h at different photon flux densities, temperatures and salinities. The initial concentrations varied widely between the cultures (α-tocopherol: 0.03 – 0.52 mg g C-1; β-carotene: 0.11 – 2.72 mg g C-1). D. tertiolecta showed increased α-tocopherol content in response to increased photon flux density. The cultures of P. minimum, P. tricornutum and S. costatum showed an increase and N. spumigena a decrease of α-tocopherol concentration with increasing temperature. Photon flux density and temperature in combination were of significant importance only for the R. salina cultures. In N. spumigena and P. tricornutum cultures, α-tocopherol concentrations increased with increasing salinity and temperature, whereas in D. tertiolecta cultures the opposite was found. In P. minimum and S. costatum cultures, salinity did not influence α-tocopherol concentration significantly. β-carotene and α-tocopherol were positively associated with each other except in D. tertiolecta and P. tricornutum. Only in one of twelve cases associations between α-tocopherol / super oxide dismutase and β-carotene / super oxide dismutase were found. It can be concluded that besides species composition of phytoplankton communities, differences in temperature and salinity contribute to the variation in antioxidant synthesis. Thus consumers must be adapted to a varying antioxidant pool.
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| 11. |
- Häubner, Norbert, et al.
(författare)
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The analysis of vitamin E in phyto- and zooplankton samples
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Vitamin E (a-tocopherol in particular) is one of the major and most potent lipid-soluble antioxidants in vivo. It is produced by autotrophs and is essential in the diet of heterotrophs. In the last decades deficiencies of essential substances such as astaxanthin and vitamin B1 (thiamine) were discovered in aquatic top predators and underlying causes seem to be food-web related. In the case of vitamin E, there is a lack of studies on the mechanisms of production and transport in aquatic food webs, which is partly related to complicated extraction procedures and high detection limits. This paper presents an improved method for the extraction and detection of a-, g- and d-tocopherol in low-biomass plankton samples. The method uses N,N-dimethylformamide (DMF) and n-hexane as extraction solvents with sodium dodecyl sulphate (SDS) as additive. This improves extraction yield and simplifies the extraction procedure because elaborate homogenization and saponification steps are unnecessary and extraction time is decreased to 1 min. Quantification of vitamin E is performed with high performance liquid chromatography (HPLC) using electrochemical detection (ECD). Detection limits of the new method are 18.5, 16.3 and 8.0 pg injected and 0.74, 0.65 and 0.32 ng mL-1 extract for a-, g- and d-tocopherol, respectively. Altogether, this is a reliable, fast and sensitive method which will allow more detailed investigations of vitamin E dynamics in aquatic food webs.
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| 12. |
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| 13. |
- Johansson, Johanna, et al.
(författare)
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Charasomer i svenska kransalger
- 2002
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Ingår i: Svensk Botanisk Tidskrift. ; 96, s. 256-259
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Tidskriftsartikel (refereegranskat)
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| 14. |
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| 15. |
- Luis Godinez-Ortega, Jose, et al.
(författare)
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Growth and pigment composition in the red alga Halymenia floresii cultured under different light qualities
- 2008
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Ingår i: Journal of Applied Phycology. - : Springer Science and Business Media LLC. - 0921-8971 .- 1573-5176. ; 20:3, s. 253-260
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Tidskriftsartikel (refereegranskat)abstract
- Halymenia floresii is an edible species consumed in some Asian markets. In the Yucatan peninsula coast of Mexico, H. floresii dominates rocky substrata between 3 and 40 m where it grows up to 50 cm high. After analyzing the seasonal pattern of pigment content on H. floresii, we evaluate if and how the spectral composition of light affects growth and pigment dynamics under laboratory cultivation. Unialgal cultures were exposed to white, blue, red and green light in a 3-week experiment. Green light resulted in the highest algal growth rates. Synthesis of chlorophyll a, alpha-carotene and lutein, but not of beta-carotene, was induced by white or green light. Phycocyanin synthesis was stimulated by blue light and phycoerythrin synthesis by blue or red light. Light quality treatments may be used to manipulate pigment composition in Halymenia floresii cultures.
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| 16. |
- Nie, Xiang-Ping, et al.
(författare)
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Prey diversity and prey stomach contents affect astaxanthin levels in piscivorous fish
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Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590.
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 20. |
- Reid, P.C., et al.
(författare)
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A biological consequence of reducing Arctic ice cover : Arrival of the Pacific diatom Neodenticula seminae in the North Atlantic for the first time in 800000 years
- 2007
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 13:9, s. 1910-1921
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Tidskriftsartikel (refereegranskat)abstract
- The Continuous Plankton Recorder survey has monitored plankton in the Northwest Atlantic at monthly intervals since 1962, with an interegnum between 1978 and 1990. In May 1999, large numbers of the Pacific diatom Neodenticula seminae were found in Continuous Plankton Recorder (CPR) samples in the Labrador Sea as the first record in the North Atlantic for more than 800 000 years. The event coincided with modifications in Arctic hydrography and circulation, increased flows of Pacific water into the Northwest Atlantic and in the previous year the exceptional occurrence of extensive ice-free water to the North of Canada. These observations indicate that N. seminae was carried in a pulse of Pacific water in 1998/early 1999 via the Canadian Arctic Archipelago and/or Fram Strait. The species occurred previously in the North Atlantic during the Pleistocene from∼1.2 to∼0.8 Ma as recorded in deep sea sediment cores. The reappearance of N. seminae in the North Atlantic is an indicator of the scale and speed of changes that are taking place in the Arctic and North Atlantic oceans as a consequence of regional climate warming. Because of the unusual nature of the event it appears that a threshold has been passed, marking a change in the circulation between the North Pacific and North Atlantic Oceans via the Arctic. Trans-Arctic migrations from the Pacific into the Atlantic are likely to occur increasingly over the next 100 years as Arctic ice continues to melt affecting Atlantic biodiversity and the biological pump with consequent feedbacks to the carbon cycle.
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| 21. |
- Schubert, H., et al.
(författare)
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Relationship between photosynthesis and non-photochemical quenching of chlorophyll fluorescence in two red algae with different carotenoid compositions
- 2006
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Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 149:5, s. 1003-1013
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Tidskriftsartikel (refereegranskat)abstract
- Algae are continuously exposed to short-term fluctuations in irradiance. We investigate how two red algae species regulate photosynthetic efficiency to cope with such changes and identify some strategies that differ from higher plants. Two red algae, Gracilaria domingensis and Kappaphycus alvarezii, with antheraxanthin and lutein as major xanthophylls, respectively, reacted to the onset of low light (below E-k) with a substantial decrease of NPQ. This is different from higher plants, but similar to previous observations in, e.g. cyanobacteria where it indicates an increase in the effective absorbance cross-section of Photosystem II (PSII) by state transition. Kinetic studies in continuous light revealed a high susceptibility of PSII to light stress ((1-q(P))/NPQ) in K. alvarezii immediately after the sudden onset of high light, followed by a decrease. This was caused by a slower onset of NPQ in K. alvarezii, followed by acclimation. In G. domingensis, susceptibility of PSII to light stress was stable with time, but absolute values of (1-q(P))/NPQ were higher than in K. alvarezii. These observations suggest that K. alvarezii may be better adapted to high light levels, but is less well prepared for large sudden changes in irradiation. In K. alvarezii, photosynthesis continued to increase with increasing irradiation when NPQ was saturated. As (1-q(P)) and NPQ were still balanced in this situation, most likely, processes other than photosynthetic oxygen release are responsible for the increasing net O-2 production observed.
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| 22. |
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| 23. |
- Snoeijs, Pauli, et al.
(författare)
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Seasonal variation of astaxanthin production in a changing pelagic ecosystem
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The carotenoid pigments of mesozooplankton communities in the Baltic Sea area were investigated in a large-scale survey. Ninety-nine percent of the zooplankton carotenoid concentrations consisted of astaxanthin and only 1% of canthaxanthin. We recorded large seasonal differences in astaxanthin concentrations, but no apparent patterns in the regional distribution within the Baltic Sea proper. Astaxanthin levels were lowest in summer when zooplankton feeding and growth rates are highest. In the cold season astaxanthin concentrations were three to four times higher than in summer and the proportions of astaxanthin esters were much higher than in summer. This suggests that astaxanthin is necessary especially in winter for the antioxidant protection of storage lipids. The seasonal cycles of astaxanthin was strongly intertwined with seasonal environmental conditions and changes in zooplankton community composition. Large differences between cladoceran- and copepod-dominated communities were were discovered. The abundances of the cladoceran genera Bosmina, Evadne and Podon were strongly negatively correlated with community concentrations of all forms of astaxanthin. Among the copepods, Temora longicornis and Pseudocalanus acuspes had the highest affinities with astaxanthin and Acartia spp. the lowest. The proportion of astaxanthin esters in the mesozooplankton of the Baltic Sea proper was on average 35%, which is lower than normally reported for pelagic crustaceans. This may indicate starvation of zooplankton and low nutritional value as astaxanthin source for predators in the Baltic Sea proper. Climate change scenarios for the area predict developments towards higher water temperature and lower salinity in the near future and this may lower the food quality for planktivorous fish if the abundances of Bosmina spp. and Acartia spp. increase at the cost of more nutritious copepods with higher astaxanthin concentrations. Because of their small size these taxa are normally avoided as prey by the major planktivorous fish, herring and sprat, in the Baltic Sea proper. However, when the abundances of larger zooplankton decrease by the ongoing bottom-up and top-down pressures on the zooplankton community, which already has happened in the case of Pseudocalanus acuspes, this may have consequences for the transport of astaxanthin to higher trophic levels.
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| 24. |
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| 25. |
- Sylvander, Peter, et al.
(författare)
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The thiamine (vitamin B1) content of phytoplankton is affected by temperature, photon density and salinity
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Ingår i: Marine Ecology Progress Series. - 0171-8630 .- 1616-1599.
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Tidskriftsartikel (refereegranskat)abstract
- Thiamine (vitamin B1) is produced by plants, algae and bacteria and must be acquired through the food web by higher trophic levels. In this study we investigate the biosynthesis of thiamine in six phytoplankton species belonging to five different phyla under different environmental conditions. The chlorophyte Dunaliella tertiolecta, the dinoflagellate Prorocentrum minimum and the prymnesiophyte Rhodomonas salina were found to be thiamine auxotrophs, while the cyanobacterium Nodularia spumigena and the diatoms Phaeodactylum tricornutum and Skeletonema costatum were capable of thiamine synthesis. Measured net thiamine production in the latter three species varied with temperature, photon density and salinity. These effects were different for the cyanobacterium and the diatoms and strongest for salinity. In N. spumigena, the total thiamine concentration increased threefold with increased salinity. P. tricornutum accumulated seven times more thiamine diphosphate when salinity was decreased. Temperature also had pronounced effects on thiamine concentration, while photon density only affected thiamine levels in combination with temperature. In N. spumigena and P. tricornutum, total thiamine levels increased with higher temperature. We demonstrate a high variability among phytoplankton species in thiamine biosynthesis, as well as in the level of thiamine production in response to environmental factors. Thus, regime shifts in phytoplankton community composition through large-scale environmental change can alter the vitamin B1 availability for higher trophic levels. This may have serious consequences for the access of zooplankton, fish, birds and mammals to this essential vitamin in changing ecosystems.
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| 26. |
- Ulanova, Anna, et al.
(författare)
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Coastal diatom-environment relationships in the brackish Baltic Sea
- 2009
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 45:1, s. 54-68
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Tidskriftsartikel (refereegranskat)abstract
- High-quality calibration data sets are required when diatom assemblages are used for monitoring ecological change or reconstructing palaeo-environments. The quality of such data sets can be validated, in addition to other criteria, by the percentage of significant unimodal species responses as a measure of the length of an environmental gradient. This study presents diatom-environment relationships analyzed from a robust data set of diatom communities living on submerged stones along a 2,000 km long coastline in the Baltic Sea area, including 524 samples taken at 135 sites and covering a salinity gradient from 0.4 to 11.4. Altogether, 487 diatom taxa belonging to 102 genera were recorded. Detrended canonical correspondence analysis showed that salinity was the overriding environmental factor regulating diatom community composition, while exposure to wave action and nutrient concentrations were of secondary importance. Modeling the abundances of the 58 most common diatom taxa yielded significant relationships with salinity for 57 taxa. Twenty-three taxa showing monotonic responses were species with optimum distributions in freshwater or marine waters. Thirty-four taxa showing unimodal responses were brackish-water species with maximum distributions at different salinities. Separate analyses for small (cell biovolume <1,000 μm3) and large (≥1,000 μm3) taxa yielded similar results. In previous studies along shorter salinity gradients, large and small epilithic diatom taxa responded differently. From our large data, we conclude that counts of large diatom taxa alone seem sufficient for indicating salinity changes in coastal environments with high precision.
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| 27. |
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| 28. |
- Ulanova, Anna, et al.
(författare)
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Lunella garyae sp nov - A new polyhalobous diatom from the English Channel coast
- 2006
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Ingår i: Diatom Research. - 0269-249X .- 2159-8347. ; 21:2, s. 415-426
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Tidskriftsartikel (refereegranskat)abstract
- A new benthic polyhalobous diatom species, Lunella garyae, is described from supralittoral limestone rock pools at Dancing Ledge, English Channel coast, England. The detailed morphology of this species is examined using scanning electron microscopy (SEM) and light microscopy (LM). The new species is compared with the two previously described Lunella species and with some other morphologically similar diatom taxa. The identity of the genus Lunella is discussed.
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| 29. |
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| 30. |
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| 31. |
- Van Nieuwerburgh, Lies, et al.
(författare)
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Astaxanthin production in marine pelagic copepods grazing on two different phytoplankton diets
- 2005
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Ingår i: Journal of Sea Research. - : Elsevier BV. - 1385-1101 .- 1873-1414. ; 53:3, s. 147-160
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Tidskriftsartikel (refereegranskat)abstract
- The red carotenoid astaxanthin is a powerful natural antioxidant of great importance in aquatic food webs where it is abundant in eggs and body tissues of fish and crustaceans. Little is known about the impact of the phytoplankton diet on astaxanthin production in copepods, its major pelagic producers. We followed the transfer of carotenoids from phytoplankton to copepods in a mesocosm experiment on the northern Atlantic coast (Norway) and recorded the astaxanthin production in copepods. Wild copepods grazed on nutrient-manipulated phytoplankton blooms, which differed in community composition and nutrient status (nitrogen or silicate limitation). The copepod pigments consisted mainly of free astaxanthin and mono- and diesters of astaxanthin. We found no significant difference in astaxanthin production per copepod individual or per unit C depending on the phytoplankton community. However, in the mesocosms astaxanthin per unit C decreased compared with natural levels, probably through a lower demand for photoprotection by the copepods in the dense phytoplankton blooms. The total astaxanthin production per litre was higher in the silicate-limited mesocosms through increased copepod density. Pigment ratio comparisons suggested that the copepod diet here consisted more of diatoms than in the nitrogen-limited mesocosms. Silicate-saturated diatoms were less grazed, possibly because they could invest more in defence mechanisms against their predators. Our study suggests that the production of astaxanthin in aquatic systems can be affected by changes in nutrient dynamics mediated by phytoplankton community composition and copepod population growth. This bottom-up force may have implications for antioxidant protection at higher trophic levels in the food web.
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| 32. |
- Van Nieuwerburgh, Lies, 1973-
(författare)
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Experimental Studies on the Regulation of Pigment Dynamics in Phytoplankton and Copepods by Dissolved Inorganic Nutrients
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 33. |
- Van Nieuwerburgh, Lies, et al.
(författare)
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Growth and C:N:P ratios in copepods grazing on N- or Si-limited phytoplankton blooms
- 2004
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Ingår i: Hydrobiologia. - 0018-8158 .- 1573-5117. ; 514:1-3, s. 57-72
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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- Wänstrand, Ingrid, 1968-
(författare)
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Pigment and Thiamine Dynamics in Marine Phytoplankton and Copepods
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Based on a field study and several mesocosm experiments, I evaluated the use of pigments as chemotaxonomical biomarkers for phytoplankton community composition in the Baltic Sea and I examined effects of inorganic nutrients on the dynamics of carotenoids and thiamine (vitamin B1) at the phytoplankton–copepod level in marine pelagic food webs. My results show that HPLC pigment analysis combined with CHEMTAX data processing was an accurate alternative to microscopic analysis of Baltic Sea phytoplankton. Experimental supply of N, P and Si affected copepod growth and biochemical status via changes in biomass and composition of their phytoplankton diet. Net population growth rates were generally higher when phytoflagellates dominated (low Si:N ratio) and lower when diatoms dominated (high Si:N ratio). Copepod body concentrations of astaxanthin decreased with fertilization. Correlations with reduced under-water irradiance were consistent with the photo-protective function of this antioxidant. Thiamine concentrations in phytoplankton also decreased with fertilization. In copepods, low Si:N ratios resulted in higher thiamine concentrations than high Si:N ratios. Thiamine concentration and degree of phosphorylation were useful as indicators of thiamine shortage both in phytoplankton and copepods. The concentrations of thiamine and astaxanthin in the copepod communities were positively correlated. As copepods constitute a major link between pelagic primary producers and higher trophic levels, fertilization effects may be responsible for astaxanthin and thiamine deficiencies in salmon suffering from the M74 syndrome, which appeared concurrently with large-scale eutrophication in the Baltic Sea. As both thiamine and astaxanthin are deficient in M74-affected salmon, there is a need for physiological and molecular investigations of possible interactions between the two compounds in living cells.
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