Effects of solar radiation on the endemic Mediterranean red alga Rissoella verruculosa: photosynthetic performance, pigment content and the activities of enzymes related to nutrient uptake

Abstract

The effects of full‐spectrum solar radiation and of solar radiation deprived of total u.v. radiation (λ<395 nm) on the endemic Mediterranean red alga Rissoella verruculosa (Bertoloni) J. Agardh were studied in situ in early summer, from sunrise to sunset. Photosynthetic performance, pigment content and the activities of enzymes related to nutrient uptake, were monitored under both radiation conditions throughout a daylight period. The doses of solar radiation, measured on the day during which the experiments were carried out (24 June 1997), were 9228·25, 1109·70 and 13·03 kJ m−2 for PAR (λ=400–700 nm), u.v.‐A (λ=315–400 nm) and u.v.‐B (λ=280–315 nm), respectively. Under these conditions, a clear daily variation in photosynthetic performance was found. However, no significant differences were detected between the two radiation conditions. At noon, strong sunlight impaired O2 evolution by 75%, but complete recovery occurred during the afternoon, reaching similar values to those measured in the early morning. By contrast, photoinhibition of optimal quantum yield (Fv/Fm), and the relative electron transport rate was followed by only a slight recovery during the afternoon. The rate of photosynthesis in air (simulating emersion conditions), estimated by CO2 exchange, showed a negative balance at noon, which was accentuated in plants exposed to the full‐solar spectrum. Significant changes in the activities of nitrate reductase and carbonic anhydrase were found throughout the day under both radiation conditions. In thalli receiving solar radiation deprived of u.v., total CA activity decreased throughout the day. However, in thalli exposed to full‐spectrum solar radiation, the activity of the enzyme tended to increase in the afternoon, correlating with an increase in NR activity.

Zonation patterns of benthic communities in an upwelling area from the western Medierranean (La Herradura, Alboran Sea)

“…Nevertheless, none of these last species have been found (e.g. Posidonia oceanica, Cystoseira spinosa), with the exception of Rissoella verruculosa, a mediolittoral species that does not appear in our sublittoral samples, but which is present in La Herradura (Flores-Moya et al, 1998).…”

Acclimation of Red Sea macroalgae to solar radiation: photosynthesis and thallus absorptance

“…Photoinhibition has been proposed as a strategy for photoprotection against high irradiance (Hanelt 1998). Several studies focusing on the effects of natural UVR on the photosynthetic performance of macroalgae from high exposure environments have revealed that the occurrence of photoinhibition under high solar radiation depends basically on daily changes in the level of irradiance, algal position on the shore, vertical light attenuation, or a combination of all these factors , Flores-Moya et al 1998.…”

Ultraviolet radiation shapes seaweed communities

“…In plants, pigments of the photosynthetic apparatus can also be destroyed by UV exposure (Strid et al 1990), with the phycobilins being the most sensitive, and carotenoids generally being less affected than the chlorophylls (Teramura 1983; Hä der and Hä der 1989). As a consequence of a number of molecular effects, several physiological processes are impaired, such as photosynthesis (Bornman 1989;Strid et al 1990;Nogues and Baker 1995;Allen et al 1997), and nutrient uptake (Dö hler 1985(Dö hler , 1992Flores-Moya et al 1998;Gó mez et al 1998), while others, e.g., respiration, appear to be less affected (Larkum and Wood 1993;Aguilera et al 1999). Photosynthesis is probably the most intensively studied process in plant biology.…”