| 1. |
- Brutemark, Andreas, et al.
(författare)
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Carbon isotope signature variability among cultured microalgae: Influence of species, nutrients and growth
- 2009
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 372:1-2, s. 98-105
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Tidskriftsartikel (refereegranskat)abstract
- In this study we have investigated whether the carbon isotopic signature differs between different groups and species of marine phytoplankton depending on growth phase, nutrient conditions and salinity. The 15 investigated algal species, representing the Bacillariophyceae, Chlorophyceae, Cryptophyceae, Cyanophyceae, Dinophyceae and Haptophyceae classes were grown in batch monocultures and analysed for delta C-13 in both exponential and stationary phase. For all the cultured species, delta C-13 signatures ranged from -23.5 parts per thousand (Imantonia sp.) to - 12.3 parts per thousand (Nodulania spumigena) in the exponential phase and from - 18.8 parts per thousand (Amphidinium carterae) to - 8.0 parts per thousand (Anabaena lemmermannii) in the stationary phase. Three species (Dunaliella tertiolecta, Rhodomonas sp.. Heterocapsa triquetra) were also grown under nutrient sufficient and nitrogen or phosphorus deficient conditions. Nitrogen limitation resulted in a more negative delta C-13 signature, whereas no effect could be observed during phosphorus limitation compared to nutrient sufficient conditions. Growth of Prymnesium parvum in two different salinities resulted in a more negative delta C-13 signature in the 26 parts per thousand-media compared to growth in 7 parts per thousand-media. Our results show that the carbon isotopic signature of phytoplankton may be affected by salinity, differ among different phytoplankton species, between exponential and stationary phase, as well as between nutrient treatments. (C) 2009 Elsevier B.V. All rights reserved.
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| 2. |
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| 3. |
- Granéli, Edna, et al.
(författare)
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Nitrogen in Inland Seas
- 2008. - 2nd Edition
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Ingår i: Nitrogen in the Marine Environment. - San Diego : Academic Press. - 9780123725226
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Lindehoff, Elin, et al.
(författare)
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Effect of tertiary sewage effluent additions on Prymnesium parvum cell toxicity and stable isotope ratios
- 2009
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Ingår i: Harmful Algae. - : Elsevier BV. - 1878-1470 .- 1568-9883. ; 8:2, s. 247-253
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the ability of the ichthyotoxic haptophyte Prymnesium parvum to use sewage-originated nutrients applying stable carbon (C) and nitrogen (N) isotope techniques. P. parvum was cultured under N and phosphorus (P) sufficient and deficient conditions in either sewage effluent-based medium or in a nitrate- and phosphate-based control. Cell densities and toxicities were monitored and stable carbon N isotopes signatures (delta C-13 and delta N-15) of P. parvum and the sewage effluent analysed. Nitrogen and P sufficient cultures achieved the highest biomass followed by P and N deficient cultures, regardless of sewage effluent additions. The P deficient cultures with sewage effluent had higher toxicity, estimated as haemolytic activity (9.4 +/- 0 x 10(-5) mg Saponin equiv. cell(-1)) compared to the P deficient control and to all N deficient and NP sufficient cultures. Nutrient deficient conditions had no effect on the cell delta N-15, but a decreasing effect on delta C-13 in the inorganic N deficient treatment. Growth in sewage-based media was followed by a substantial increase in the cell delta N-15 (10.4-16.1.60) compared to the control treatments (2.4-4.9%o), showing that P. parvum is capable of direct use of sewage-originated N, inorganic as well as organic. Uptake of terrestrial derived C in the sewage treatments was confirmed by a decrease in cell delta C-13, implying that P. parvum is able to utilize organic nutrients in sewage effluent. (C) 2008 Elsevier B.V. All rights reserved.
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| 5. |
- Barreiro, A, et al.
(författare)
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Relative importance of the different negative effects of the toxic haptophyte Prymnesium parvum on Rhodomonas salina and Brachionus plicatilis
- 2005
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 38:3, s. 259-267
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to determine the relative importance of the different processes/mechanisms by which the toxic haptophyte Prymnesium parvum, cultured under different nutrient conditions, affects non-toxic phytoplankton competitors and microzooplankton grazers. P. parvum was cultured under steady-state growth in different nutrient conditions: nitrogen depleted (-N), phosphorus depleted (-P) and balanced nitrogen and phosphorus (+NP). Cells from each nutrient condition and culture cell-free filtrates, alone and combined with non-toxic prey (Rhodomonas salina), were used as food for the rotifer Brachionus plicatilis. An additional experiment was carried out to test the effect of P. parvum cells and culture cell-free filtrate on R. salina. The highest haemolytic activity values were achieved by -P F parvum cultures, followed by -N. However, the negative effect of R parvum on R. salina and rotifers did not correlate with haemolytic activity but with the number of P. parvum cells. -N-cultured P. parvum were the most toxic for both R. salina and rotifers, followed by +NP. Therefore, haemolytic activity is not a good indicator of the total potential toxicity of R parvum. The growth rate of R. salina was negatively affected by cell-free filtrates but the effect of P, parvum predation was greater. Rotifers fed on both toxic and non-toxic algae, indicating that they did not select against the toxic alga. The P. parvum cell-free filtrate had an effect on B. plicatilis, although this was weak, B, plicatilis was also indirectly affected by P. parvum due to the negative effects of the toxic alga on their prey (R. salina). However, the greatest negative effect of P. parvum on the rotifers was due to ingestion of the toxic cells. Therefore, the phytoplankton competitor R. salina is more affected by P. parvum predation and the grazer B. plicatilis is more affected by ingestion of the toxic cells, the effects of excreted compounds being secondary.
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| 6. |
- Carvalho, Wanderson, et al.
(författare)
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Dinophysis norvegica (Dinophyceae), more a predator than a producer?
- 2008
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Ingår i: Harmful Algae. - : Elsevier B.V. - 1568-9883 .- 1878-1470. ; 7:2, s. 174-183
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Tidskriftsartikel (refereegranskat)abstract
- Several studies have proved that some Dinophysis species are capable of ingesting particulate organic matter besides of being photosynthetic, a form of nutrition termed mixotrophy. Phagotrophy may be an important aspect of the life history of the genus Dinophysis and the key to understand its ecology. We used modern techniques coupling flow cytometry and acidotropic probes to detect and score food vacuolated Dinophysis norvegica cells in natural samples. In addition, feeding experiments were conduced under controlled conditions to observe if D. norvegica would grow feeding on the cryptophyte Teleaulax amphioxeia. The results of the field observations showed a frequency of phagotrophy between 25 and 71% in a natural D. norvegica population from the Baltic Sea, which is higher than previous reports (1–20%). Although molecular methods have proved that the kleptoplastids of the D. norvegica from the Baltic Sea are from T. amphioxeia, the laboratory experiments showed that the presence of T. amphioxeia in the cultures did not enhance the survival rate of D. norvegica neither in phototrophic nor in heterotrophic conditions. We suggest that the D. norvegica Kleptoplats are obtained through a heterotrophic or mixotrophic protist, which have been feeding on cryptophytes, as it has recently been shown for Dinophysis acuminata. Our main conclusion is that D. norvegica, and probably all other species from the genus Dinophysis, is mainly phagotrophic and feeds on a larger prey than T. amphioxeia. Autotrophy through kleptoplastidy would be a secondary feature used as a complementary or short-term survival strategy.
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| 7. |
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| 8. |
- Fistarol, GO, et al.
(författare)
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Allelopathic effect on a nutrient-limited phytoplankton species
- 2005
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 41:2, s. 153-161
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Tidskriftsartikel (refereegranskat)abstract
- For aquatic systems, studies on allelopathic interactions among phytoplankton have increased over recent years, with the main focus on the role of the donor organism. In this study, we report on the response of a target organism to allelochemicals and whether this response was affected by stress conditions (nutrient limitation). We exposed the diatom Thalassiosira weissflogii, grown under different nitrogen (N) and phosphorus (P) conditions (NP, -N, or -P), to single or daily additions of a cell-free filtrate of Prymnesium parvum (grown with no nutrient limitation). When we exposed T weissflogii to a single addition of filtrate, all 3 treatments were inhibited by P. parvum. However, T weissflogii NP was the most resistant, while T weissflogii -N showed the highest sensitivity to P. parvum filtrate, followed by T weissflogii -P. When T weissflogii was exposed. to daily additions of P. parvum, the degree of inhibition of all T weissflogii treatments was higher than when only 1 initial addition was made. In this case, even the treatment that had the highest resistance (T weissflogii NP) was not only inhibited by the filtrate, but also showed a decrease in cell numbers. Nevertheless, T weissflogii -N was still more sensitive than the other treatments. Therefore, nutrient-limiting conditions may increase allelopathic effects, by making the target more susceptive to allelopathic compounds. Under these conditions, allelopathy may play a strong role in phytoplankton competition, especially in natural environments where the allelochemicals are continuously released and, thus, the target species do not have time to recover.
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