LIGHT RESPIRATION IN SIX ESTUARINE PHYTOPLANKTON SPECIES: CONTRASTS UNDER PHOTOAUTOTROPHIC AND MIXOTROPHIC GROWTH CONDITIONS1

Authors

  • Alan J. Lewitus,

    Corresponding author
    1. Belle W. Baruch Institute for Marine Biology and Coastal Research, Baruch Marine Field Laboratory, University of South Carolina, P.O. Box 1630, Georgetown, South Carolina 29442
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  • Todd M. Kana

    1. University of Maryland System, Center for Environmental and Estuarine Studies, Horn Point Environmental Laboratory, P.O. Box 775, Cambridge, Maryland 21613
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  • 1

    Received 27 December 1994. Accepted 16 May 1995.

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ABSTRACT

The photoresponse of respiration was examined in six estuarine phytoplankton species grown at a limiting irradiance in the presence or absence of glucose. Cellular respiration rates in the dark, at the growth irradiance, and at saturating light levels were higher in glucose-grown cultures than in photoautotrophic cultures. Glucose uptake also affected the relationship between incident irradiance and gross respiration rate, and the specific respiratory pathways that contributed to the respiration versus irradiance (R vs. I) response. The energy-conseming Mehler reaction contributed largely to light-stimulated respiration in photoautotrophic (energy-limited) cultures. However, the energy-dissipating alternative pathway was the predominant form of respiration measured in mixotrophic (energy-sufficient) cultures. Based on these and previous observations, a model of phytoplankton R us. I response is presented, in which the relative contributions of different light respiratory processes (cytochrome pathway respiration, alternative pathway respiration, chlororespiration, Mehler reaction) are dependent on the incident irradiance and cellular energy content.

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