Sensitivity of intertidal and subtidal red algae to UVA and UVB radiation, as monitored by Chlorophyll fluorescence measurements: Influence of collection depth and season, and length of irradiation

Abstract

Thirteen species from the red algal flora of Helgoland (southern North Sea) were exposed to UVA ÷ UVB radiation for various periods in the laboratory, and dark-adapted variable fluorescence (F v : Fro) was measured immediately after the UV treatment and again after various recovery times in white light. With the exception of Porphyra ~mbilicalis, all species showed a decrease in F v : F m on exposure to UV radiation, followed by recovery towards the initial values during the next 24-48 h in white light. The rate of the initial decrease was greater, and the extent of recovery was less, in deep subtidal species (e.g. Delesseri~ s~guinea, Placamium carfflagineum) than in intertidal or shallow subtidal species, although there was no direct correlation between these indicators of sensitivity to UV radiation and the depth range of a species, and only slight differences were detected between populations of a single species collected from different depths. There was also little evidence of a seasonal change in sensitivity to UV radiation in Delesseria or Plocamium. The decrease in variable fluorescence in Delesseria and Plocamium was proportional to the logarithm of the exposure to UV radiation, and reciprocity between irradiance and the length of irradiation appeared to hold for up to ~6h. The exposure to UVA that reduced F~ : F m by 50% ('50% exposure') immediately after the treatment was about I0 kJ m -2 for both Delesseria and Plocamium, but Plocamium appeared to recover more rapidly than Delesseria because the 50% exposure after 24 h recovery was about 37 kJ m -2 for Delesseria compared with 70-120 kJ m -z for different populations of Plocamium. The removal of UVB from the UV radiation treatments had no detectable effect o~ the inhibition of F v : F~ in either Ddesseria or a deep-water population of Plocamium, but reduced the inhibition by 30-50% in a shallow-water population of Plocamium. When only half an intact blade of De]esseria was exposed to UV radiation, variable fluorescence was reduced in the irradiated half but was completely unaffected in the unirradiated half, and steep gradients of Fv : F m values were measured which persisted for over 48 h after the irradiation treatment.

Sensitivity of freshwater macrophytes to UV radiation: relationship to depth zonation in an oligotrophic New Zealand lake

“…Thus, deeper-growing species display a greater decrease of F v /F m in response to UVR exposure than do shallower-growing species. This type of relationship between photoinhibition and depth distribution has been reported previously for several species of marine macroalgae (Dring et al 1996;Hanelt et al 1997;Hanelt 1998;Bischof et al 2000b) and zooxanthellate corals (Shick et al 1995).…”

“…It has also been shown that organisms can have markedly different tolerances of UVR (e.g. Bothwell et al 1993;Dring et al 1996;Vinebrooke and Leavitt 1999). These observations have given rise to considerations of what role UVR may currently play in structuring aquatic communities.…”

Ultraviolet radiation shapes seaweed communities

“…Hitherto, there is agreement that the species sensitivity to solar radiation stress is a function of depth distribution (Dring et al 1996b;Larkum and Wood 1993;Hanelt et al 1997a, c;Hanelt 1998;Bischof et al 1998a;Yakovleva et al 1998). Moreover, some authors regard solar UVB as one of the most important factors controlling the upper distribution limit of seaweeds in the field (Maegawa et al 1993).…”

“…For the vertical distribution of tropical seagrasses UV radiation was also proven to be an important factor (Dawson and Dennison 1996). Dring et al (1996b) showed that sensitivity to UV in red algae growing around the island of Helgoland (Germany) varies with species and depth of collection. As for UVB radiation, investigations on the photoinhibition induced by high levels of PAR also shows a correlation between depth-zonation and the ability for dynamic photoinhibition of macroalgae both from sublittoral (Hanelt 1992(Hanelt , 1998Hanelt et al 1994Hanelt et al , 1997a and intertidal populations In support of this concept the green algae Enteromorpha bulbosa and Acrosiphonia arcta which occur in the middle and lower eulittoral at the Antarctic Peninsula (Wiencke and Clayton 2002) do almost show no negative UV-effects on photosynthesis and are able to acclimate to even further elevated UV-exposure within hours or days .…”

Insights into the red algae and eukaryotic evolution from the genome of Porphyra umbilicalis (Bangiophyceae, Rhodophyta)

“…Porphyra is frequently exposed to elevated intensities of UV radiation in the intertidal zone and shows remarkable tolerance to both UV-A and UV-B (50,51). Porphyra has at least two strategies to protect photosynthesis and other key cellular processes from UV damage: mycosporine-like amino acids (MAAs) and circadian control over the timing of UVsensitive processes.…”