Salt-marsh vegetation as biological indicator of increased solar UV-B radiation consequence of ozone global depletion

BIANCIOTTO; PINEDO; SAN ROMAN; BLESSIO; KOCH; COSTA

Antarctic Peninsula and Tierra del Fuego

Taylor and Francis Group plc

Lugar: Londres; Año: 2007; p. 109 - 117

In order to analyze the effects of different levels of natural UV-B radiation on dominant genera – Salicornia, Puccinellia, Spartina and Juncus – of salt-marshes in situ, UV-B attenuation experiments were done on fand margin ecosystems of middle (Juncus and Spartina), highj (Salicornia and Puccinellia) and low (Juncus) latitudes. Physiological, morphological, demographic and phenological changes generated by the effects of natural UV-B levels have been evaluated. These experiments were done with the reduction of UV spectrum short wavelengths (280-320 nm) by covering plots with UV-B opaque (Mylar) and comparing them with UV-B transparent (Aclar) plastic screens and unscreening control plots. Shoot lenght in Salicornia ambigua was not affected by UV-B attenuation. However, the contents of shielding pigments and cuticle thickness – both were lower under attenuated UV-B treaments – (25-48 % and 21-40% respectively) showed significant differences between treatments. For pigment level these effects appeared in the first part of the growing season; for cuticle thickness, along the whole period. Biomass and density of shoots were higher (17 and 40% increase) in attenuated UV-B radiation parcels. Also , at the end of the growing season (March) the number of dead shoots was lower in coincidence with the longest growing period (30 days longer). Slight changes in species compositionat community level (Salicornia-Puccinellia) were found. In Puccinellia preliminary results showed that UV-B attenuation increments vegetative growth, through higher fully expanded leaves and higher pigment content. Another salt-marsh dominant genera like Spartina and Juncus  did not display any change in growth parameters at medium and lowlatitude as the result of UV-B attenuation. Salicornia seems to be an appropriate biological indicator to allow the assessment of the significance of the ozone depletion impact upon Subantarctic ecosystems.