Laminaria saccharina photosynthesis measured in situ: photoinhibition and xanthophyll cycle during a tidal cycle

Abstract

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 (Φ 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 Φ 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.

Photosynthetic performance, DNA damage and repair in gametes of the endemic Antarctic brown alga Ascoseira mirabilis exposed to ultraviolet radiation

“…Differences in P, PA and PAB sensitivity of the optimum quantum yield in gametes were presumably caused by the degree of damage to PSII components or due to the xanthophyll cycle mediated down regulation of PSII (Gevaert et al 2003). The interactive effects of radiation and exposure time treatments, however, showed that the measurable effects of different doses of PAR and UVR in the reduction of photosynthetic efficiency can be similar but the mechanisms behind PAR-and UVR-induced inhibition of photosynthesis are different (Franklin et al 2003).…”

Phosphorylation of MAPK-like proteins in three intertidal macroalgae under stress conditions

“…Intertidal algal growth, development, reproduction and productivity are drastically affected by changes in temperature, humidity, salinity, irradiance (both photosynthetically active radiation [PAR] and ultraviolet radiation [UVR]) and nutrient availability (Dring 1982, Lobban & Harrinson 1994, Davison & Pearson 1996, Häder & Figueroa 1997, Gévaert et al 2003, Gao & Xu 2010, Karleskint et al 2010. The expected increase in atmospheric CO 2 and the concomitant ocean acidification due to global climate change might increase or negate the effect of these stressors, and the response and strategies of adaptation and acclimation to these stressors must be studied according to realistic global change scenarios.…”

Photosynthetic activity and productivity of intertidal macroalgae: In situ measurements, from thallus to community scale

“…and L. digitata. The response of Φ PSII to high irradiances was associated to an increase in the nonphotochemical quenching and was explained as a down-regulation of the photosystem II (Gévaert et al, 2003;Delebecq et al, 2011).…”