Oxidative stress and antioxidant defences generated by solar UV in Subantartic marine phytoflagellate.

HERNANDO M; MALANGA G; FERREYRA G

SCIENTIA MARINA

Año: 2005 vol. 69 p. 287 - 295

0214-8358

Summary   The reduction of the Antarctic stratospheric ozone resulted in significant increases in ultraviolet B radiation (UVB, 280-320 nm) reaching the surface of the ocean. The main goal of this work was to study long-term (growth rate scale, days) stress responses (lipid oxidative damage, expressed as tiobarbituric acid reactive substances (TBARS) content, and lipid soluble antioxidant content) to UV-B and UV-A on a phytoflagellate species (Prasinophyceae) isolated from a natural phytoplankton community of the Subantarctic Beagle Channel. A marked increase in the content of TBARS was observed at the first day of the experiment, showing significant differences between algae subjected to UV-B and UV-A treatments, thus suggesting high damage to the cell membrane.  During the second day of the experiment TBARS in UV-A treatments were higher than in the PAR one. Concentration of TBARS decreased to the level of the PAR control on the third day, remaining low until the end of the experiment. Lipid antioxidant concentrations (£\-tocopherol and £]-carotene) were lagged with respect to variations in TBARS, presenting maximum values at the third day of the experiment. This coincided with the minimum TBARS concentrations in all treatments. The content of both antioxidants  increased significantly on cultures exposed to UV-B and UV-A on days three and four. In the Antarctic species (phytoflagellate, AP and Thalassiosira sp., AT) a-tocopherol was more abundant than ƒÒ-carotene. Phytoflagellate species showed a lag in reaching the maximum content of both antioxidants in relation with AT, which presented the maximum concentration within a short time scale (3 h) suggesting a more rapid response to oxidative stress. AT was more tolerant to UVR stress than phytoflagellate species. Overall, our results show that UVR damage/repair balance involves the combined action of several internal factors in the cell.