BRYOZOANS INCREASE AVAILABLE CO2 FOR PHOTOSYNTHESIS IN GELIDIUM SESQUIPEDALE (RHODOPHYCEAE) |
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Authors: | Jesú s M. Mercado,Raquel Carmona,F. Xavier Niell |
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Affiliation: | Departamento de Ecología, Facultad de Ciencias, Universidad de Málaga, Campus Universitario de Teatinos, 29071 Málaga, Spain |
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Abstract: | A possible benefit of the presence of the epiphytic bryozoan Electra pilosa (L.) for the red macroalga Gelidium sesquipedale (Clem.) Thuret et Bornet is described. Absorption spectra and photosynthetic parameters of O2 evolution vs. irradiance curves were determined for both epiphytized and nonepiphytized thalli. The absorptance of G. sesquipedale thalli for PAR was not modified by the presence of the epiphyte. Gross photosynthetic rates at saturating light were approximately doubled in epiphytized thalli. Photosynthesis by G. sesquipedale was enhanced when CO2 concentration was increased in the medium by a decrease in pH. On the other hand, an increase in pH from 8.1 to 8.7 produced a significant reduction of the O2 evolution rates indicating that G. sesquipedale has a very low capacity to use HCO3−. The decrease in photosynthesis at high pH was higher in nonepiphytized thalli than in epiphytized ones, suggesting that the amount of available CO2 is higher in the presence of E. pilosa. This positive effect was attributed to the CO2 released by respiration of the epiphyte. |
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Keywords: | bryozoan Gelidium sesquipedale inorganic carbon macroalga pH photosynthesis respiration |
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