Growth form defines physiological photoprotective capacity in intertidal benthic diatomsReport as inadecuate

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* Corresponding author 1 LIENSs - LIttoral ENvironnement et Sociétés - UMR 7266 2 MMS - EA 2160 Mer, molécules, santé 3 Universiteit Gent Ghent 4 Fachbereich Biologie Konstanz 5 CNRS - Centre National de la Recherche Scientifique

Abstract : In intertidal marine sediments, characterized by rapidly fluctuating and often extreme lightconditions, primary production is frequently dominated by diatoms. We performed a comparativeanalysis of photophysiological traits in 15 marine benthic diatom species belonging to the fourmajor morphological growth forms epipelon EPL, motile epipsammon EPM-M and non-motileepipsammon EPM-NM and tychoplankton TYCHO found in these sediments. Our analysesrevealed a clear relationship between growth form and photoprotective capacity, and identified fastregulatory physiological photoprotective traits that is, non-photochemical quenching NPQ and thexanthophyll cycle XC as key traits defining the functional light response of these diatoms. EPMNMand motile EPL showed the highest and lowest NPQ, respectively, with EPM-M showingintermediate values. Like EPL, TYCHO had low NPQ, irrespective of whether they were grown inbenthic or planktonic conditions, reflecting an adaptation to a low light environment. Our resultsthus provide the first experimental evidence for the existence of a trade-off between behaviouralmotility and physiological photoprotective mechanisms NPQ and the XC in the four majorintertidal benthic diatoms growth forms using unialgal cultures. Remarkably, although motilityis restricted to the raphid pennate diatom clade, raphid pennate species, which have adopted anon-motile epipsammic or a tychoplanktonic life style, display the physiological photoprotectiveresponse typical of these growth forms. This observation underscores the importance of growthform and not phylogenetic relatedness as the prime determinant shaping the physiologicalphotoprotective capacity of benthic diatoms.

Author: Alexandre Barnett - Vona Méléder - Lander Blommaert - Bernard Lepetit - Wim Vyverman - Koen Sabbe - Christine Dupuy - Johann La



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