Impact of UV-radiation on viability, photosynthetic characteristics and DNA of brown algal zoospores:implications for depth zonation

Abstract

Measurements of photosynthesis, germination capacity and assessment of DNA damage were carried out in the laboratory to determine the effect of different conditions of ultraviolet (W) and photosynthetically active radiation (PAR) on zoospores of various large brown algae collected on Spitsbergen (Svalbard, High Arctic) and Tarifa (Cbdiz, southern Spain). Results were correlated to in situ light conditions and indicated that zoospores suffer photoinhibition of photosynthesis, loss of viability and DNA damage in relation to the growth depth of parental sporophytes. At both sites, germination capacity of zoospores in species collected in deep waters was more strongly mpaired after exposure to the same UV doses than in species from shallower waters. In general, zoospores exposed to PAR+UVA+UVB showed higher mortality rates than after exposure to PAR+UVA or PAR alone. For Larmnana digitata from Spitsbergen, it was found that the loss of zoospore viability is the result of DNA damage and photodamage of the photosynthetic apparatus. UVB irradiances occurring in southern Spain at water depths shallower than 7 m prevented the germination of spores of deep water Laminariales from this region.

Ultraviolet radiation shapes seaweed communities

“…The UV susceptibility of the photosynthesis and of the DNA in spores is unequivocally related to the depth distribution of the macrothalli as outlined above (see chapters 5.1, 5.1.1.3; Bischof et al 2000a;Wiencke et al 2000;Roleda et al 2004Roleda et al , 2005a. Other negative effects of UV radiation especially on macroalgal spores presumably important for determination of the upper distribution limit concern the cytoskeleton.…”

“…The zoospores e.g. of the more advanced families of the Laminariales, the Alariaceae, Laminariaceae and Lessoniaceae only contain one small chloroplast (Henry and Cole 1982), with comparatively low photosynthetic activity (Amsler and Neushul 1991;Wiencke et al 2000). Storage lipids are certainly the main energy source of spores, supporting swimming and potentially germination processes (Brezezinski et al 1993;Reed et al 1999).…”

Exposure to ultraviolet radiation delays photosynthetic recovery in Arctic kelp zoospores

“…In Arctic Laminaria digitata (Huds.) Lamour., photosynthesis of zoospores was significantly depressed under the whole light spectrum compared to the sporophytes (Wiencke et al 2000).…”

“…Further studies on this aspect, especially on the early life stages of macroalgae, should be carried out. For example, effect of UVR on the photosynthesis of reproductive cells has been studied only in few species of Laminariales (Dring et al 1996;Wiencke et al 2000;Roleda et al 2005) and Ulvales (Cordi et al 2001). Among the three Laminaria species in Helgoland, photoinhibition of zoospore photosynthesis to different light treatments, consisting of the whole light spectrum and excluding UV-B or UV-B+UV-A, and the capacity of recovery of their photosynthetic efficiencies was found to be related to the depth distribution of adult sporophytes (Roleda et al 2005).…”

Photosynthetic response and zonation of three species of Gelidiales from Tenerife, Canary Islands

“…Thus, inter-specific competition has usually been the consensus for the main cause of zonation (Chapman, 1973(Chapman, , 1974. However, experimental studies propose that physiological limits of seaweeds are also involved in zonation (Dring & Brown, 1982;Rico & Fredriksen, 1996;Wiencke & al., 2000;Bischof & al., 2006).…”