Publication

2003

English

http://archimer.ifremer.fr/doc/00000/10191/7592.pdf (0.24 Mo)

Gevaert F, Creach A, Davoult D, Migne A, Levavasseur G, Arzel Pierre, Holl Ac, Lemoine Y

Univ Sci & Technol Lille, Equipe Ctrophysiol Vegetale & Phycol, CNRS, UMR 8013,ELICO, F-59655 Villeneuve Dascq, France.
Univ Paris 07, CNRS, UMR 7127, F-29682 Roscoff, France.
Univ Paris 06, Lab Hydrobiol, IFR 101, F-75005 Paris, France.
IFREMER, Ctr Brest, Lab Cotier, F-29280 Plouzane, France.

Marine Ecology Progress Series (0171-8630) (Inter-research), 2003 , Vol. 247 , P. 43-50

26

Ecology

Laminaria saccharina, photoprotection, xanthophyll cycle, chlorophyll fluorescence, diurnal tidal cycles, diving PAM

Photosynthetic activity in thalli of Laminaria saccharina (Lamouroux) was followed in situ in the upper subtidal zone of a Northern Brittany rocky shore (Roscoff, France), using a submersible pulse amplitude modulated (PAM) fluorometer. Two fluorescence parameters, the effective quantum yield of photosystem II (Phi(PSII)) and the relative electron transport rate (rETR), were estimated at various stages of a tidal cycle from 10:00 to 18:30 h, and different light conditions due to variations of water depth and position of the sun. The Phi(PSII) decreased strongly during the ebb tide, essentially due to a drop in the maximal fluorescence level for light-adapted samples (F-m'). This was the result of increasing non-photochemical quenching (NPQ). Algae totally recovered during the rising tide, indicating that no significant photosynthetic damage occurred at ebb tide. L. saccharina responded to high light stress with photoprotective processes such as the xanthophyll cycle. The de-epoxidation ratio (DR) (i.e. conversion of violaxanthin into antheraxanthin and zeaxanthin) increased during the ebb tide and decreased during the rising tide. However, in spite of the development of a photoprotective mechanism, the overall photosynthetic activity (rETR) declined strongly at the highest irradiance level. This result indicates that primary production levels have been overestimated in the past.