Migration or photoacclimation to prevent photoinhibition and UV-B damage in marine microphytobenthic communities.

J.-L. Mouget (1) , Rupert Perkins (2) , Mireille Consalvey (3) , Sébastien Lefebvre (4, 5)

1 Laboratoire de Biochimie et Physiologie Végétales
2 School of Earth, Ocean and Planetary Sciences [Cardiff]
3 NIWA - National Institute of Water and Atmospheric Research [Wellington]
4 ECOBIO - Ecosystèmes, biodiversité, évolution [Rennes]
5 LOG - Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187

Microphytobenthos (MPB) on intertidal mudflats is a major component of primary pro- ducers in some estuarine ecosystems. To sustain photosynthesis, MPB migrate through the upper sed- iment layer and form transient biofilms during emersion periods, and thus may be exposed to high irradiance and ultraviolet radiation (UV-R), possibly resulting in photodamage to the photosynthetic apparatus. In contrast, downard migration could allow cells to optimize position in the photic zone, avoiding photoinhibitory light levels. Engineered biofilms with inhibited migratory capacity were used to distinguish between possible strategies (photoacclimation or migration) evolved by MPB to cope with photoinhibitory irradiances, when a series of UV filters with different cut-off wavelengths was used to estimate the respective contribution of visible light and UV-R. Engineered biofilms with full migratory capacity maintained a high relative electron transport rate (rETR), in contrast to engi- neered non-migratory biofilms, which showed a decrease in rETR under high irradiance, with a greater decrease under UV-B radiation. Migration thus appeared to be the principal short-term mechanism allowing MPB to avoid or minimize UV-R and high PAR photodamage in situ. Neverthe- less, physiological acclimation processes to different light levels (‘light-shade’ patterns) seem to occur in the long term, and probably superimpose on migratory capacity, making light history an important component of MPB photoacclimation strategies.

Mots clés: Microphytobenthos; Migration; Photodamage; Photoinhibition; Ultraviolet radiation

Domaines: Planète et Univers [physics]

J.-L. Mouget, Rupert Perkins, Mireille Consalvey, Sébastien Lefebvre. Migration or photoacclimation to prevent photoinhibition and UV-B damage in marine microphytobenthic communities.. Aquatic Microbial Ecology, 2008, 52, pp.223-232. ⟨hal-00481246⟩