UVR acclimation responses in two phytoplankton species from the Patagonian coast: Effects of increased temperature

HALAC, S.R.; VILLAFAÑE, V. E.; HELBLING, E. W.

Mar del Plata

Congreso; The Changing Coastal and Estuarine Environment: A Comparative Approach; 2012

Coastal and Estuarine Research Federation

We studied the UVR long-term responses in a scenario of increased temperature of two marine phytoplankton species ? the dinoflagellate Proorocentrum micans and the chlorophyte Dunaliella salina. We evaluated photoacclimation as related to the photochemical performance (yield) and photoprotective strategies (i.e. synthesis of UV-absorbing compounds or changes in chlorophyll content per cell). Cultures were exposed to solar radiation under two radiation treatments, UVR+PAR (280-700 nm) and PAR only (400-700 nm) and two temperatures: in situ surface spring/summer water (control, 15/18ºC) and increased temperature (+5°C, 20/23ºC) during 5-7 days. Additionally, the effects of attenuated radiation (by 50%) were determined. Significant decrease in yield at noon was determined in all samples, but P. micans had a clear trend of increasing the noon yield throughout the experiment, suggesting an efficient photoacclimation process which was related to the increasing amounts of UV-absorbing compounds. However, D. salina had higher sensitivity to solar radiation, but increased temperature diminished the UVR- negative effect; moreover, D. salina presented the highest photochemical performance under the PAR (attenuated) treatment and high temperature. Our results highlight for important interspecific differences in the UVR acclimation capacity; under a scenario of climate change, species with less photoacclimation capacity would be more affected by the interaction between radiation and temperature.