DIEL CYCLE IN THE CONCENTRATION OF UV-ABSORBING COMPOUNDS IN

MARÍA ALEJANDRA MARCOVAL; DONAT P. HÄDER; PETER RICHTER; E.WALTER HELBLING

La Plata, Argentina

Congreso; VIII Encuentro Latinoamericano de Fotoquímica y Fotobiología; 2004

The diel dynamics of potencially photoprotective compounds (i.e. UV-absorbing at 280- 400 nm) in red algae species of coastal Patagonia, was determined considering the time of exposure to solar radiation and the tidal cycle. Samples of four species of Rodophyta (Ceramium sp., Corallina officinalis, Callithamnion gaudichaudii and Porphyra columbina) were collected in the intertidal zone of Barrancas Blancas beach (43°S, 65°W). As a result of the semi-daily tide, sampling was carried out for two weeks in February-March 2004, taking samples every hour during the low tide, in order to sample species with different light history, hence establishing the diel cycle. The concentration of UV-absorbing compounds (i.e. mycosporine like amino acids, MAAs), carotenoids and photoprotective pigments, was determined by spectrophotometric analysis and chromatography (HPLC). In three species (Ceramium sp., C. gaudichaudii and P. columbina), a decrease in the concentration of UV-absorbing compounds was registered, from high values during the night to low values during the day, in accordance to the radiation received. In C. officinalis it was observed a diel cycle with relatively high concentration of UV-absorbing compounds with low radiation and low concentrations with high radiation (i.e. mid-day). This inverse relation was also observed for the concentration of carotenoids in C. officinalis and Ceramium sp. Thus, we may conclude that C. officinalis and Ceramium sp. respond to irradiance with a gradual recovery of UV-absorbing compounds after local mid-day. However, the other species studied respond accordingly to the dosis, with a continual drop of UV-absorbing compounds during the day without showing any further recovery.