Quality of UVR exposure for different biological systems along a latitudinal gradient.

VERNET, MARIA; DIAZ, SUSANA; FUENZALIDA, HUMBERTO; CAMILION, CAROLINA; BOOTH, CHARLES R.; CABRERA, SERGIO; CASSICCIA, CLAUDIO; DEFERRARI, GUILLERMO; LOVENGREEN, CHARLOTTE; ALEJANDRO PALADINI; ROSALES, ALEJANDRO; ZAGARESE, HORACIO

PHOTOCHEMISTRY AND PHOTOBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2009 vol. 8 p. 1329 - 1345

0031-8655

Exposure of organisms to ultraviolet radiation (UVR) is characterized by the climatology (or annual cycle) and the variance (or anomalies) in biologically weighted irradiances at eight geographical locations in austral South America, from 1995-2002. Net effect of UVR on biological systems is a result of the balance of damage and repair which depends on intensity and duration of irradiance and is modulated by its variability. The emphasis in this study is on day-to-day variability, a time scale of importance to the development of adaptive strategies that counteract UVR damage in biological systems. The irradiances were weighted with DNA- and phytoplankton photosynthesis-action spectra. As expected, low latitude sites show higher average UVR. For all sites, the frequency of days with above average irradiances is higher than below average irradiances. Persistence in anomalies is generally low, (~ 0.2 autocorrelation coefficient), but higher for DNA-weighted- than phytoplankton-weighted irradiances due to their higher correspondence to stratospheric ozone. Cloudiness is highly correlated to UVR anomalies in low latitudes (28°-33° S) and ozone correlates higher in high latitudes (42°-55° S). Our results show that organisms in this region deal with several days of excess radiation and fewer, shorter and more intense periods of lower than average radiation. Relief from UVR stress (or higher frequency of days with below average irradiance) is more prevalent in high latitudes (55° S). Thus, lower latitudes are more stressful to organisms not only because of higher average UVR irradiances but also for the higher frequency of days with above average irradiances.