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- Lundgren, Veronica, et al.
(författare)
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Metabolic and physiological changes in Prymnesium parvum when grown under, and grazing on prey of, variable nitrogen:phosphorus stoichiometry
- 2016
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883 .- 1878-1470. ; 55, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Mixotrophy is found in almost all classes of phytoplankton in a wide range of aquatic habitats ranging from oligotrophic to eutrophic marine and freshwater systems. Few studies have addressed how the nutritional status of the predator and/or the prey affects mixotrophic metabolism despite the realization that mixotrophy is important ecologically. Laboratory experiments were conducted to examine changes in growth rates and physiological states of the toxic haptophyte Prymnesium parvum when fed Rhodomonas sauna of varying nutritional status. Haemolytic activity of P. parvum and prey mortality of R. sauna were also measured. P. parvum cultures grown to be comparatively low in nitrogen (low-N), phosphorus (low-P) or low in both nutrients (low-NP) were mixed with low-NP, low-N, and low-P R. saline in all possible combinations, i.e., a 3 x 3 factorial design. N deficiency was obtained in the low-N cultures, while true P deficiency may not have been obtained in the low-P cultures. Mortality rates of R. salina (both due to ingestion and/or cell rupture as a function of grazing or toxic effects) were higher when R. sauna cells were low-P, N-rich, regardless of the nutritional state of P. parvum. Mortality rates were, however, directly related to the initial prey:predator cell ratios. On the other hand, growth of the predator was a function of nutritional status and a significant positive correlation was observed between growth rates of P. parvum and cell-specific depletion rates of N, whereas no such relationship was found between P. parvum growth rates and depletion rates of P. In addition, the greatest changes in chlorophyll content and stoichiometric ratios of P. parvum were observed in high N:P conditions. Therefore, P. parvum may show enhanced success under conditions of higher inorganic N:P, which are likely favored in the future due to increases in eutrophication and altered nutrient stoichiometry driven by anthropogenic nutrient loads that are increasingly enriched in N relative to P. (C) 2016 Elsevier B.V. All rights reserved.
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| 2. |
- Vidyarathna, Nayani K., et al.
(författare)
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The effects of aeration on growth and toxicity of Prymnesium parvum grown with and without algal prey.
- 2014
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Ingår i: Harmful Algae. - : Elsevier. - 1568-9883 .- 1878-1470. ; 39, s. 55-63
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the effects of aeration on growth and toxicity of the haptophyte Prymnesium parvum in the presence and absence of the algal prey Rhodomonas salina. Batch monocultures of P-limited P. parvum and N and P sufficient R. salina and mixed cultures of the two microalgae were grown with no, low (20) and high (100) ml min1 aeration for 18 days. Cell growth of P. parvum and R. salina and cell toxicity of P.parvum were studied over the experimental period. The highest specific growth rates of P. parvum were found at low aeration rates. R. salina in monocultures showed typical growth patterns, while R. salina numbers declined rapidly in the mixed cultures. Of the initial cell densities, 98–100% of the R. salina cells were lysed or ingested within 24 h of mixing with P. parvum cells. The maxima P. parvum biomasses were significantly higher in the mixed cultures than in the monocultures. Cell toxicity of P. parvum increased significantly in response to aeration rates and the highest levels were found in the high aeration condition. Availability of prey and resupply of inorganic nutrients decreased P. parvum cell toxicity. Our study suggests that P. parvum is tolerant and is able to grow over a broad range of aeration and associated turbulence effects though low aeration represents an optimal condition for growth. As P. parvum toxicity was higher in the high aeration treatment we suggest that the higher concentrations of oxygen cause more toxins to be produced, as these are oxygen rich compounds. We suggest that oxygenation and turbulence of surface waters caused by mixing may be involved in promoting high toxic P. parvum blooms in shallow lakes and coastal waters.
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