STREAM PERIPHYTON PHOTOACCLIMATION RESPONSE IN FIELD CONDITIONS: EFFECT OF COMMUNITY DEVELOPMENT AND SEASONAL CHANGES1 |
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Authors: | Martin Laviale Jean Prygiel Yves Lemoine Adeline Courseaux Anne Créach |
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Institution: | 1. Laboratoire de Génétique et Evolution des Populations Végétales, UMR CNRS 8016, Université des Sciences et Technologies de Lille – Lille1, F‐59655 Villeneuve d’Ascq cedex, France;2. Present address: Laboratoire Mer, Molécules et Santé, EA 2160, Université de Nantes, 2 rue de la Houssinière, BP 92208, F‐44322 Nantes Cedex 3, France.;3. Agence de l’Eau Artois‐Picardie, 200 rue Marceline, F‐59508 Douai cedex, FranceProcessus et Bilans des Domaines Sédimentaires, UMR CNRS 8110, Université des Sciences et Technologies de Lille – Lille 1, F‐59655 Villeneuve d’Ascq cedex, France;4. Laboratoire d’Océanologie et de Géosciences, UMR CNRS 8187, Université des Sciences et Technologies de Lille – Lille 1, F‐59655 Villeneuve d’Ascq cedex, France;5. Author for correspondence: e‐mail . |
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Abstract: | The photochemical behavior of intact stream periphyton communities in France was evaluated in response to the time course of natural light. Intact biofilms grown on glass substrata were collected at three development stages in July and November, and structural parameters of the biofilms were investigated (diatom density and taxonomy). At each season, physiological parameters based on pigment analysis (HPLC) and pulse‐amplitude‐modulated (PAM) chl fluorescence technique were estimated periodically during a day from dawn to zenith. Regardless of the community studied, the optimal quantum yield of PSII (Fv/Fm), the effective PSII efficiency (ΦPSII), the nonphotochemical quenching (NPQ), and the relative electron transport rate (rETR) exhibited clear dynamic patterns over the morning. Moreover, microalgae responded to the light increase by developing the photoprotective xanthophyll cycle. The analysis of P‐I parameters and pigment profiles suggests that July communities were adapted to higher light environments in comparison with November ones, which could be partly explained by a shift in the taxonomic composition. Finally, differences between development stages were significant only in July. In particular, photoinhibition was less pronounced in mature assemblages, indicating that self‐shading (in relation to algal biomass) could have influenced photosynthesis in older communities. |
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Keywords: | PAM fluorescence photoacclimation photoadaptation photoinhibition photoprotection stream periphyton xanthophyll cycle |
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