PHOTOACCLIMATION IN THE TROPICAL CORALLINE ALGA HYDROLITHON ONKODES (RHODOPHYTA, CORALLINACEAE) FROM A FRENCH POLYNESIAN REEF 

Authors

  • Claude E. Payri,

    Corresponding author
    1. Laboratoire d'Ecologie Marine, Université de la Polynésie Française, BP 6570, Faaa/Aéroport, Tahiti, French Polynesia
    Search for more papers by this author
  • Stéphane Maritorena,

    1. Laboratoire d'Ecologie Marine, Université de la Polynésie Française, BP 6570, Faaa/Aéroport, Tahiti, French Polynesia, and
      Institute for Computational Earth System Science, University of California at Santa Barbara, Santa Barbara, California 93106
    Search for more papers by this author
  • Christophe Bizeau,

    1. Laboratoire d'Ecologie Marine, Université de la Polynésie Française, BP 6570, Faaa/Aéroport, Tahiti, French Polynesia
    Search for more papers by this author
  • Michel Rodière

    1. Laboratoire d'Ecologie Marine, Université de la Polynésie Française, BP 6570, Faaa/Aéroport, Tahiti, French Polynesia
    Search for more papers by this author

Author for correspondence: e-mail payri@ufp.pf.

Abstract

Pigment concentration, in vivo absorption, and photosynthetic parameters of the coralline alga Hydrolithon onkodes (Heydrich) Penrose and Woelkerling were compared among samples from a lagoon and from a reef crest of Tahiti Island. Four groups of specimens were considered, differing in their natural exposure to PAR. For specimens collected from the lagoon, the tissues from low-light samples had significantly higher pigment concentration, particularly chl a and phycobilins, compared with the high-light exposed plants that contained more total carotenoids. The in vivo absorption spectra normalized to chl a (called a* values) also revealed differences. The low-light samples had a reduced absorption capacity and a well-marked phycobilin absorption signature, whereas sunlit samples showed a greater absorption at wavelengths absorbed mainly by chl a and carotenoids. The decrease of a* when pigment concentration increased is interpreted as a consequence of the pigment packaging. Significantly lower α (chlorophyll basis) and higher Ek values were found in the shaded plants. The values of Pmax for the four groups of specimens were not significantly different. The samples showed various degrees of photoinhibition depending on the light exposure during growth, and this effect was more pronounced in the shaded plants. The specimens from the reef crest deviate from the general model presented for the lagoon samples and show a mix of sun- and shade-exposed characteristics. We have shown that the coralline alga H. onkodes responds to its light environment, probably by acclimation rather than ecotypic genetic variation, by adjusting its physiology, but some morphological differences are also involved. Photoacclimation can explain partly the wide distribution of this species over the reef ecosystem and its major contribution to the building of the reef.

Ancillary