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Growth and grazing responses of Chrysochromulina ericina (Prymnesiophyceae): the role of irradiance, prey concentration and pH
Hansen, P.J.; Hjorth, M. (2002). Growth and grazing responses of Chrysochromulina ericina (Prymnesiophyceae): the role of irradiance, prey concentration and pH. Mar. Biol. (Berl.) 141(5): 975-983. http://hdl.handle.net/10.1007/s00227-002-0879-5
In: Marine Biology. Springer: Heidelberg; Berlin. ISSN 0025-3162, more
Peer reviewed article  

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Keyword
    Marine

Authors  Top 
  • Hansen, P.J.
  • Hjorth, M.

Abstract
    The effect of irradiance, prey concentration and pH on the growth and grazing responses of the mixotrophic prymnesiophyte Chrysochromulina ericina under N-and P-replete conditions was studied using the pedinophyte Marsupiomonas pelliculata as prey. The two organisms were inoculated in monocultures and in mixed cultures at different predator: prey ratios at three irradiances and allowed to grow for 4–7 days. All cultures were non-axenic. Algal densities and pH were monitored throughout the experiments and growth and grazing rates were measured. An increase in growth of C. ericina cultures at irradiances of 25 and 70 µmol photons m-2 s-1 was observed after the addition of prey, while growth of C. ericina cultures at the high irradiance (150 µmol photons m-2 s-1) was unaffected by the addition of prey. However, although the growth of C. ericina increased at low irradiance (25 µmol photons m-2 s-1), it did not reach the same level as monocultures at the high irradiance (150 µmol photons m-2 s-1), suggesting that phagotrophy can only partly replace photosynthesis in C. ericina. Maximum growth rates of C. ericina at irradiances of 25 and 70 µmol photons m-2 s-1 were obtained at concentrations of > 0.15–0.3×105 M. pelliculata ml-1, corresponding to 50–100 µg C 1-1. Ingestion of M. pelliculata cells by C. ericina did not generally follow Michaelis—Menten kinetics. Deviation from the expected saturation kinetics was especially pronounced at irradiances of 70 and 150 µmol photons m-2 s-1. At these irradiances ingestion of M. pelliculata cells by C. ericina decreased at high concentrations of M. pelliculata, indicating an increased uptake of bacterial prey in these cultures. The growth rate of C. ericina was affected in both monocultures and in mixed cultures when pH increased above 8.6, and growth stopped around pH 9. The prey alga M. pelliculata tolerated high pH better and, consequently, took over in the mixed cultures when pH exceeded 9. The ecological significance of mixotrophy in the genus Chrysochromulina is discussed.

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