Algae. 2009; 24(2): 93-104.
Form, Function and Longevity in Fucoid Thalli: Chlorophyll a Fluorescence Differentiation of Ascophyllum nodosum, Fucus vesiculosus and F. distichus (Phaeophyceae)
Kwang Young Kim1* and David J. Garbary2
1Department of Oceanography, Chonnam National University, Gwangju 500-757, Korea
2Department of Biology, St. Francis Xavier University, Antigonish, Nova Scotia, B2G 2W5, Canada
Imaging-PAM fluorometry was used to assess the chlorophyll a fluorescence parameter ΦPSII (effective quantum yield) in Fucus vesiculosus, F. distichus ssp. distichus and Ascophyllum nodosum. The objective was to show variation in fluorescence yield associated with age and frond organ, and to illustrate the spatial scales at which photosynthetic parameters vary on fucoid thalli. In addition, our species represented taxa in different but related genera, species with different ecologies (rock pool and non rock pool species), morphologies (with and without air bladders) and longevities (several to 20 or more years). A further objective was to determine the extent to which photosynthetic parameters reflected these differences. Effective quantum yield declined substantially with age in F. vesiculosus and F. distichus ssp. distichus, whereas ΦPSII in A. nodosum was maximal after three years. In A. nodosum ΦPSII was still high in branch segments at least seven years old. Older branches of A. nodosum showed relatively higher and more homogeneous photosynthetic capacity relative to Fucus species. Surfaces of air bladders in A. nodosum and F. vesiculosus had ΦPSII that was not significantly different from the highest rates achieved in these species. The heterogeneity of photosynthetic efficiency is consistent with morphological and developmental differences among the species and their ecology, in particular the longevity of A. nodosum fronds.
Keywords : Ascophyllum, chlorophyll a fluorescence, development, effective quantum yield, Fucus, photosynthesis