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Marine Ecology Progress Series

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MEPS 416:93-103 (2010)  -  DOI:

Vertical cell movement is a primary response of intertidal benthic biofilms to increasing light dose

R. G. Perkins1,*, J. Lavaud2, J. Serôdio3, J. L. Mouget4, P. Cartaxana5, P. Rosa6, L. Barille6, V. Brotas5, B. M. Jesus5,7

1School of Earth, Ocean and Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3YE, UK
2UMR CNRS 6250 ‘LIENSs’, Institute for Coastal and Environmental Research (ILE), University of La Rochelle, 2 rue Olympe de Gouges, 17042 La Rochelle Cedex, France
3Departamento de Biologia, Universidade de Aveiro, Aveiro 3810-193, Portugal
4Laboratoire de Physiologie et Biochimie Végétales, Faculté des Sciences et Techniques, Université du Maine, EA2663, Av. O. Messiaen, 72085 Le Mans Cedex 9, France
5Centro de Oceanografia, Faculdade de Ciências da Universidade de Lisboa, Lisboa 1749-016, Portugal
6EA 2160 ‘Mer, Molécules, Santé’, Faculté des Sciences et Techniques, Université de Nantes, 2 rue de la Houssinière, BP 92208, 44322 Nantes cedex 3, France
7Centro de Biodiversidade, Genómica Integrativa e Funcional (BioFIG), Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal

ABSTRACT: Intertidal soft sediment microphytobenthic biofilms are often dominated by diatoms, which are able to regulate their photosynthesis by physiological processes (e.g. down-regulation through the xanthophyll cycle, referred to as non-photochemical quenching, NPQ) and behavioural processes (e.g. vertical cell movement in the sediment–biofilm matrix). This study investigated these 2 processes over a 6 h emersion period using chemical inhibitors under 2 light treatments (ambient and constant light at 300 µmol m–2 s–1). Latrunculin A (Lat A) was used to inhibit cell movement and dithiothreitol (DTT) to inhibit NPQ. HPLC analysis for chlorophyll a and spectral analysis (Normalised Difference Vegetation Index) indicated that Lat A significantly inhibited cell movement. Photosynthetic activity was measured using variable chlorophyll fluorescence and radiolabelled carbon uptake and showed that the non-migratory, Lat A-treated biofilms were severely inhibited as a result of the high accumulated light dose (significantly reduced maximum relative electron transport rate, rETRmax, and light utilisation coefficient, α, compared to the migratory DTT and control-treated biofilms). No significant patterns were observed for 14C data, although a decrease in uptake rate was observed over the measurement period. NPQ was investigated using HPLC analysis of xanthophyll pigments (diatoxanthin and the percentage de-epoxidation of diadinoxanthin), chlorophyll fluorescence (change in maximum fluorescence yield) and the 2nd order spectral derivative index (diatoxanthin index). Patterns between methods varied, but overall data indicated greater NPQ induction in the non-migratory Lat A treatment and little or no NPQ induction in the DTT and control treatments. Overall, the data resulted in 2 main conclusions: (1) the primary response to accumulated light dose was vertical movement, which when inhibited resulted in severe down-regulation/photoinhibition; (2) diatoms down-regulated their photosynthetic activity in response to accumulated light dose (e.g. over an emersion period) using a combination of vertical migration and physiological mechanisms that may contribute to diel and/or tidal patterns in productivity.

KEY WORDS: Benthic · Diatom · Down-regulation · Migration · Photophysiology · Productivity

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Cite this article as: Perkins RG, Lavaud J, Serôdio J, Mouget JL and others (2010) Vertical cell movement is a primary response of intertidal benthic biofilms to increasing light dose. Mar Ecol Prog Ser 416:93-103.

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