title: A five-year study of solar ultraviolet radiation in southern Chile (39 degrees S): potential impact on physiology of coastal marine algae?
abstract: This study reports 5 years of (1998-2003) data on continuous solar-irradiation measurements from a scanning spectroradiometer (SUV-100) in Valdivia, Chile (39 degrees S), accompanied by evaluation of the impact of ultraviolet radiation (UVR) on marine macroalgae of this site. UVR conditions showed a strong seasonal variation, which was less pronounced toward longer wavelengths. Daily maximum dose rates (clear days) averaged in winter-summer: UV-B(290-315 nm) 0.30-2.1, UV-B(290-320 nm) 0.70-3.7, UV-A(315-400 nm) 20.6-62.1, UV-A(320-400 nm) 20.2-60.5 W m(-2), and photosynthetically active radiation (PAR) 969-2423 micromol m(-2) s(-1). The corresponding daily doses (all the days) ranged: UV-B(290-315 nm) 2.6-40.7, UV-B(290-320 nm) 6.7-78.5, UV-A(315-400 nm) 228-1539, UV-A(320-400 nm) 224-1501, and PAR 2008-13308 kJ m(-2) d(-1). Taking into consideration action spectra of a biological interest, the risk of UV exposure could be up to 37 times higher in summer than in winter. The photosynthetic activity (as maximum quantum yield of chlorophyll fluorescence, F(v)/F(m)) of the brown alga Lessonia nigrescens from the infralittoral zone was markedly more sensitive to UVR than of the green alga Enteromorpha intestinalis from the upper midlittoral, and the UV-B wave band increased markedly photoinhibition. In L. nigrescens, maximal photoinhibition (40%) took place at weighted (the action spectrum for photoinhibition of photosynthesis) UVR doses of 800 kJ m(-2), irrespective of the season (corresponding midsummer daily dose in Valdivia is 480 kJ m(-2)). In winter, when this alga was at its most sensitive, the weighted UV dose causing 35-40% photoinhibition was around 200 kJ m(-2). In E. intestinalis, weighted doses of 800 kJ m(-2) resulted in low photoinhibition (<10 %) and no clear seasonal patterns could be inferred. These results confirm that midday summer levels of UV-B and their daily doses in southern Chile are high enough to produce stress to intertidal macroalgae.
authors.affiliation: Universidad Austral de Chile, Facultad de Ciencias, Instituto de Biología Marina, Campus Isla Teja s/n, Casilla 567, Valdivia, Chile. phuovinen@ulagos.cl
authors.forename: Pirjo
authors.initials: P
authors.lastname: Huovinen
authors.forename: Iván
authors.initials: I
authors.lastname: Gómez
authors.forename: Charlotte
authors.initials: C
authors.lastname: Lovengreen
mesh_terms: D000818:Animals; D002677:Chile; D002734:Chlorophyll / Q000737:chemistry / Q000528:radiation effects*; D000460:Chlorophyta / Q000502:physiology / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005453:Fluorescence; D010788:Photosynthesis / Q000528:radiation effects*; D012621:Seasons; D012623:Seawater; D012993:Solar Energy; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D002734:Chlorophyll