UVR effects photosynthetic yield of Prorocentrum minimum (Pavillard) Schiller and Dunaliella salina Teodoresco in a simulated water column

PETER RICHTER,; P HADER, DONAT; VIRGINIA ESTELA VILLAFAÑE; WALTER HELBLING, E

Puerto Rico

Congreso; 33rd Annual Meeting of the American Society for Photobiology; 2006

The impact of UVR on photosynthetic efficiency of Prorocentrum minimum (Pavillard) Schiller andDunaliella salina Teodoresco was investigated in vertical Plexiglas columns (depth = 65 cm, diameter= 15 cm) under artificial illumination (H nle lamp, PAR = 162 W m-2, UV-A = 32.6 W m-2 and UV-B= 1.08 W m-2). Half of the columns were covered with a 295 nm cut-off filter (thus receiving UVR(280-400 nm) and PAR) while the others with a 395 nm cut-off filter (thus receiving only PAR). Cellsamples were collected from different depths (i.e., surface, 20, 40 and 65 cm) from whichphotosynthetic efficiency parameters were determined using a pulse amplitude modulatedfluorometer Water PAM (Walz, Germany). There was a significant decrease in the photosynthetic yieldin samples exposed to UVR as compared to those receiving only PAR, but the effect decreased withdepth. The impact was also evident in the recovery dynamics: Those cells previously exposed to UVRrecovered less than those ones exposed only to PAR. Our data also show acute and chronic effects ofUVR, as well as the protective effect of attenuation in the simulated water column. Moreover,different mechanisms seem to account for the observed impact produced by UVR: WhileProrocentrum minimum was partially protected by screening substances (i.e., mycosporine-like aminoacids) Dunaliella salina, that lacks these kind of potentially protective substances, might have othervery efficient protection / repair mechanisms as its sensitivity was similar to that of P. minimum.