| 1. |
- Carlsson, Per, et al.
(författare)
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Bacterial and phytoplankton nutrient limitation in tropical marine waters, and a coastal lake in Brazil
- 2012
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 418, s. 37-45
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Tidskriftsartikel (refereegranskat)abstract
- Bioassay experiments were performed two times (with 2 years in between) in order to investigate if nitrogen (N, ammonium), phosphorus (P, phosphate) and carbon (C, glucose) additions would stimulate the growth of bacteria and phytoplankton differently in three different tropical aquatic environments. The water and their indigenous microbial communities were taken from a freshwater coastal lake (Cabiunas), a coastal (Anjos), and an offshore marine station (Sonar) in the Atlantic outside Cabo Frio, Rio de Janeiro State, Brazil. Ammonium, phosphate and glucose were added alone or in combination to triplicate bottles. In the lake, P seemed to be the primary limiting factor during the first experiment, since both bacterial production and phytoplankton growth was stimulated by the P addition. Two years later, however, addition of P inhibited phytoplankton growth. During both years, C was closely co-limiting for bacteria since CP additions increased the response considerably. For both the coastal and offshore seawater stations, phytoplankton growth was clearly stimulated by N addition in both years and the bacteria responded either to the P, N or C additions (alone or in combination). To conclude, the results from these tropical aquatic systems show that it is possible that phytoplankton and bacteria may compete for a common resource (P) in lakes, but can be limited by different inorganic nutrients in marine waters as well as lakes, suggesting that phytoplankton and bacteria do not necessarily compete for the same growth limiting nutrient in these environments. (C) 2012 Elsevier B.V. All rights reserved.
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| 2. |
- Bowers, HA, et al.
(författare)
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Combining flow cytometry and real-time PCR methodology to demonstrate consumption in Prymnesium parvum
- 2010
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Ingår i: Journal of the American Water Resources Association. - : Wiley. - 1093-474X .- 1752-1688. ; 46, s. 133-143
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Tidskriftsartikel (refereegranskat)abstract
- Harmful algal bloom species can persist in the environment, impacting aquatic life and human health. One of the mechanisms by which some harmful algal bloom species are able to persist is by consumption of organic particles. Methods to demonstrate and measure consumption can yield insight into how populations thrive. Here, we combine flow cytometry and real-time PCR to demonstrate consumption of a cryptophyte species (Rhodomonas sp.) by a toxic mixotrophic haptophyte (Prymnesium parvum). Using flow cytometry, the feeding frequency of a population of P. parvum cells was calculated using the phycoerythrin (PE) fluorescence signal from Rhodomonas sp. and the fluorescence of an acidotropic probe labeling the food vacuoles. Feeding frequency increased in the beginning of the experiment and then began to decline, reaching a maximum of 47.5% of the whole P. parvum population after 212 min. The maximum number of consumed Rhodomonas sp. cells was 0.8 per P. parvum cell, and occurred after 114 min corresponding to an ingestion rate of 0.4 Rhodomonas sp. cells/P. parvum/h. Cells from the feeding P. parvum population were sorted, washed, and subjected to a real-time PCR assay targeting the cryptophyte 18S locus. There was a correlation between cycle threshold (Ct) values and number of consumed prey cells calculated by fluorescence. Overall, this study shows that flow cytometric analysis, of the acidotropic probe and prey pigments, is an efficient and rapid tool in enumerating food vacuoles and the number of prey cells consumed. Furthermore, we suggest that real-time PCR can be applied to cells sorted by flow cytometry, thus allowing for the detection and potential quantification of the targeted prey cells.
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| 3. |
- Brutemark, Andreas, et al.
(författare)
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Role of mixotrophy and light for growth and survival of the toxic haptophyte Prymnesium parvum
- 2011
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 10, s. 388-394
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Tidskriftsartikel (refereegranskat)abstract
- Mixotrophy in Prymnesium parvum was investigated using carbon (δ13C) and nitrogen (δ15N) stable isotopes. The experiment was performed in light and dark. In the dark treatment we expected that the mixotrophic P. parvum would rely solely on its prey and therefore reflect the prey isotopic signatures. In the light treatment P. parvum can perform photosynthesis as well as utilize its prey, thus we expect the isotopic signatures to be between the dark mixed cultures and the monocultures, depending on how much prey was utilized. In the light treatment, addition of the ciliate Myrionecta rubra resulted in higher P. parvum cell numbers compared to monocultures. During the experiment, cell numbers in the dark monocultures and the mixed dark cultures did not increase. P. parvum had 2.5-3 times higher cellular phosphorus and nitrogen content in the dark compared to the cultures in the light whereas no difference in carbon content between treatments could be observed. This suggests that P. parvum can utilize nitrogen and phosphorus but not carbon in the dark. It thus seems as if P. parvum relies on photosynthesis to meet the carbon and energy demand required for growth. The expected isotopic signatures “become what you eat…plus a few per mil” were not observed. In the dark treatment, the δ13C did not differ between monocultures and mixed cultures. In the light treatments P. parvum δ13C became less negative then the corresponding dark treatments indicating that P. parvum used CO2 rather than carbon from the added prey. No difference in δ15N between monocultures and mixed cultures could be observed during the experiment. We argue that light is necessary for P. parvum growth and that the ability to utilize nutrients originating from their prey may be important in bloom formation.
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| 4. |
- F de Carvalho, Wanderson, et al.
(författare)
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Contribution of phagotrophy versus autotrophy to Prymnesium parvum growth under nitrogen and phosphorus sufficiency and deficiency
- 2010
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 9, s. 105-115
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory experiments were conducted to test the effects of nitrogen (N) and phosphorus (P) sufficiency and deficiency on mixotrophy in Prymnesium parvum (Haptophyta). A parvum was grown with and without algal prey (Rhodomonas salina) and observed for 120 h. Detection and enumeration of cells containing food vacuoles with prey (i.e. phagotrophy) was based on flow cytometric detection of fluorescence of an acidotropic probe. Overall, the presence of R. salina increased phagotrophy in P. parvum suggesting that, at least in this strain of P. parvum, the presence of suitable prey can stimulate phagotrophic behavior in P. parvum. Feeding frequency (the percentage of A parvum cells containing food vacuoles in a given time) was significantly higher under N and P deficiency than in the nutrient-sufficient treatments. A nutrient budget constructed from the data indicated that ingestion of organic matter (OM) supplied with 78 +/- 7% of the N (3.9 +/- 0.3 mu M) incorporated by P. parvum in the N-deficient treatment, and 45 +/- 9% of the P (0.3 +/- 0 mu M) acquired in the P-deficient cultures. Even under nutrient sufficiency, ingestion of OM was estimated to have supplied 43 +/- 16% of the N and 48 +/- 16% of the P incorporated into P. parvum cells. Phagotrophy was observed even in the NP-sufficient cultures (non-axenic mixed and monocultures), although P. parvum cells did not lose their photosynthetic capability, suggesting that phagotrophy is probably a permanent nutritional adaptation to this species. The ingestion of organic nutrients played an important role in P. parvum growth, being a reliable source of nutrition for P. parvum inorganic nutrient limitation, and could explain its capabilities to form persistent blooms. (C) 2009 Elsevier B.V. All rights reserved.
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| 5. |
- Flynn, Kevin J, et al.
(författare)
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Misuse of the phytoplankton-zooplankton dichotomy : the need to assign organisms as mixotrophs within plankton functional types
- 2013
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Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 35:1, s. 3-11
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Tidskriftsartikel (refereegranskat)abstract
- The classic portrayal of plankton is dominated by phytoplanktonic primary producersand zooplanktonic secondary producers. In reality, many if not most planktontraditionally labelled as phytoplankton or microzooplankton should be identifiedas mixotrophs, contributing to both primary and secondary production. Mixotrophicprotists (i.e. single-celled eukaryotes that perform photosynthesis and grazeon particles) do not represent a minor component of the plankton, as some formof inferior representatives of the past evolution of protists; they represent a majorcomponent of the extant protist plankton, and one which could become moredominant with climate change. The implications for this mistaken identification, ofthe incorrect labelling of mixotrophs as “phytoplankton” or “microzooplankton”,are great. It extends from the (mis)use of photopigments as indicators of primaryproduction performed by strict photoautotrophs rather than also (co)locating mixotrophicactivity, through to the inadequacy of plankton functional type descriptionsin models (noting that mixotrophic production in the individual organism is not asimple sum of phototrophy and heterotrophy). We propose that mixotrophy shouldbe recognized as a major contributor to plankton dynamics, with due effortexpended in field and laboratory studies, and should no longer be side-lined inconceptual food webs or in mathematical models.
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| 6. |
- Granéli, Edna, et al.
(författare)
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Blågrönalger i Östersjön (Blue-green algae in the Baltic Sea, In Swedish)
- 2010
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Ingår i: Havet 2010. - Stockholm : Naturvårdsverket/Havsmiljöinstitutet. - 1654-6741. ; , s. 35-38
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Blomningar av blågrönalger i Östersjön är inget nytt fenomen. De förekom redan för 8000 år sedan, i samband med att Östersjön blev ett brackvattenhav. Blomningarna har dock ökat i såväl utbredning som intensitet under de senaste femtio åren. Med mycket stor sannolikhet är det vi människor som ligger bakom ökningen. Det är inte heller bara en bov i dramat, utan tre; övergödning, överfiske och klimatförändring.
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| 7. |
- Granéli, Edna, et al.
(författare)
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Can increases in temperature stimulate blooms of the toxic benthic dinoflagellate Ostreopsis ovata?
- 2011
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Ingår i: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 10:2, s. 165-172
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Tidskriftsartikel (refereegranskat)abstract
- Ostreopsis ovata Fukuyo is an epiphytic, toxic dinoflagellate, inhabiting tropical and sub-tropical waters worldwide and also in certain temperate waters such as the Mediterranean Sea. Toxic blooms of O. ovata have been reported in SE Brazil in 1998/99 and 2001/02 and the French-Italian Riviera in 2005 and 2006. These blooms had negative effects on human health and aquatic life. Chemical analyses have indicated that O. ovata cells produce palytoxin, a very strong toxin, only second in toxicity to botulism. Increase in water temperature by several degrees has been suggested as the reason for triggering these blooms. Four laboratory experiments were performed with O. ovata isolated from Tyrrhenian Sea, Italy to determine the effects of water temperature and co-occurring algae on the cell growth and/or the toxicity of O. ovata. The cells were grown under different temperatures ranging from 16 °C to 30 °C, and cell densities, growth rates and the cell toxicities were studied. Results indicated high water temperatures (26-30 °C) increased the growth rate and biomass accumulation of O. ovata. In mixed cultures of O. ovata with other co-occurring algae, biomass decreased due to grazing by ciliates. Cell toxicity on the other hand was highest at lower temperatures, i.e., between 20 and 22 °C. The present study suggests that sea surface temperature increases resulted by global warming could play a crucial role inducing the geographical expansion and biomass accumulation by blooms of O. ovata.
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| 8. |
- Granéli, Edna, et al.
(författare)
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Factors influencing allelopathy and toxicity in Prymnesium parvum
- 2010
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Ingår i: Journal of the American Water Resources Association. - : Wiley. - 1093-474X .- 1752-1688. ; 46, s. 108-120
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Tidskriftsartikel (refereegranskat)abstract
- Some microalgae are able to kill or inhibit nutrient-competing microalgae, a process called allelopathy. Inhibiting or killing competitors enable these species to monopolize limiting resources, such as nitrogen and phosphorus. Prymnesium parvum is known to produce such allelopathic compounds, substances that seem identical to the ichthyotoxins identified from this species. Biotic and abiotic environmental factors influence not only growth rates but also toxin/allelopathic compounds production by P. parvum cells. Toxin production, as well as allelopathy, including grazer deterrence, increases dramatically in light, temperature, or nutrient stressed P. parvum cells. Correspondingly, toxicity and allelopathy may decrease, or cease completely, if cells are grown with high amounts of N and P in balanced proportions. However, even under nutrient (N and P) sufficient conditions, P. parvum is able to produce toxins/allelopathic compounds, with negative effects on other phytoplankton species or grazers, if cells densities of P. parvum are high relative to other species. This negative effect might shift the plankton community to more toxin resistant species. Filtrates from nutrient-deficient P. parvum cultures have almost the same strong negative effect on grazers and other phytoplankton species as when Prymnesium cells are grown together with the target organisms. Eutrophication, the increased input of N and P to aquatic ecosystems, besides increasing nutrient concentrations, is usually provoking unbalanced N:P condition for the optimal growth of phytoplankton, deviating from the Redfield ratio, i.e., the phytoplankton cellular nitrogen to phosphorus ratio, N:P = 16:1 (by atoms) or 7.2:1 (by weight). Eutrophication thus both enhances P. parvum growth and increases production of toxins and allelopathic compounds. Supplying N-deficient or P-deficient P. parvum cells with the deficient nutrient reduces toxicity to less than half within 24 h after additions. As P. parvum is mixotrophic, uptake of dissolved or particulate organic N (DON or PON) can also reduce toxicity and allelopathy in the same manner as addition of inorganic N to N-starved cells. In conclusion, P. parvum, by increasing its toxicity and allelopathic ability under poor environmental conditions, outcompetes the co-occurring phytoplankton species.
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| 9. |
- Granéli, Edna, et al.
(författare)
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Minimizing economical losses with the help of “real-time” algal surveillance
- 2012
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Ingår i: Eco-Tech 2012 Proceedings. ; , s. 550-555
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Cyanobacterial blooms covering almost the entire Baltic Sea is a yearly feature during July-August. For the tourism industry at Öland island, SE Sweden, the economical losses during the summer 2005 amounted to 17-23 million euros. Remote sensing satellite images show that all the Öland beaches are covered with decomposing algae. In reality, these blooms rarely reach the western side of the island. To more accurately inform the public on the quality of the water for swimming, with the help of volunteers, a daily real-time surveillance of the algal densities on the beaches was performed. The volunteers (from 15 years old to pensioners) were trained at the Linnaeus University, from simple laboratory techniques, to more complicated ones such as identification and enumeration of the toxic cyanobacteria species. By latest 9.00 a.m., the public had access to information on the algal situation on 17 beaches. We could show that: 1) although remote sensing images showed Öland being surrounded by the blooms, our surveillance showed no algal accumulations on the beaches 2) that the real-time warning system boosted public confidence in the local water quality and during the first “Miss Algae”-summer 2006, the economical losses by the tourism industry turned in profits, the gain amounting to 17 million euros, 3) this kind of real-time surveillance is economical feasible due to low-costs involved, but also, the project has a great social value for the volunteers who mostly were pensioners. The volunteers who participated in “Miss Algae” had a good knowledge about the area they monitored (as their houses are located nearby) and could disseminate knowledge to the public in these areas. This kind of project also render a lot of interest regional, national and international, and can be used in advertising campaigns to increase tourism in the areas affected by algal blooms.
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| 10. |
- Granéli, Edna, et al.
(författare)
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The ecophysiology and bloom dynamics of Prymnesium spp.
- 2012
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 14:SI, s. 260-270
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Tidskriftsartikel (refereegranskat)abstract
- Members of Prymnesium belong to the division Haptophyta, class Prymnesiophyceae, order Prymnesialesand family Prymnesiaceae. As most haptophytes, members of the genus Prymnesium are unicellular andplanktonic. The most known of these species is the ichthyotoxic P. parvum, which may form nearlymonospecific dense blooms in coastal and inland waters. This species possesses extraordinary plasticityconcerning life survival strategies, and is specifically addressed in this review.Toxins produced by P. parvum have hemolytic properties, that not only kill fish but also co-existingplankton. These substances are allelopathic (when other algae are killed) and grazer deterrent (whengrazers are killed). Allelopathy enables P. parvum to utilize inorganic nutrients present in the surroundingwater without competition from other algal species; and by eliminating its grazers P. parvum reduces celllosses. The paralized microalgae and/or zooplankton, are therefter ingested by the P. parvum cells, aprocess called phagotrophy. P. parvum is also able of osmotrophy, i.e. utilization of dissolved organicmatter. In this review, the cellular characteristics, life cycles, bloom formation, and factors affectingtoxicity, allelopathy, phagotrophy, and osmotrophy of P. parvum are discussed.
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