Oxidative stress and antioxidant defences generated by solar UV in a Subantarctic marine phytoflagellate

• Published in: Scientia Marina (Barcelona) Vol. 69; no. S2; pp. 287 - 295
• Main Authors: Pablo Hernando, Marcelo, Malanga, Gabriela Fabiana, Ferreyra, Gustavo Adolfo
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Consejo Superior de Investigaciones Científicas 01-12-2005
• Subjects: Asteromonas; Bacillariophyta; carotene; Flagellata; growth rate; Marine; ozone; tbars; Thalassiosira; tocopherol; uv radiation; PSW, South America, Beagle Channel
• ISSN: 0214-8358; 1886-8134
• DOI: 10.3989/scimar.2005.69s2287

The reduction of the Antarctic stratospheric ozone resulted in significant increases in ultraviolet B radiation (UV-B, 280-320 nm) reaching the surface of the ocean. The main objective of this work was to study long-term (growth rate scale, days) stress responses (lipid oxidative damage, TEARS, and lipid soluble antioxidants) to UV-B and UV-A of a phytoflagellate species (Asteromonas sp.) isolated from a natural phytoplankton community of the Subantarctic Beagle Channel. The growth rate was inhibited by UV-B and UV-A radiation during the exponential phase. A marked increase in the TBARS content was observed on day 1 of the experiment, with 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 TEARS in UV-A treatments were higher than under photosynthetically active radiation (PAR). The concentration of TBARS decreased to the level of the PAR control on day 3, remaining low until the end of the experiment. Lipid antioxidant concentrations ( alpha -tocopherol and beta -carotene) were delayed with respect to variations in TBARS, showing maximum values on day 3 of the experiment. This coincided with the minimum TEARS concentrations in all treatments. The content of both antioxidants increased significantly in cultures exposed to UV-B and UV-A on days 3 and 4. In Antarctic species (phytoflagellate Asteromonas sp., AP and diatom Thalassiosira sp., AT) alpha -tocopherol was more abundant than beta -carotene. The phytoflagellate species showed a lag in reaching the maximum content of both antioxidants in relation to AT, which reached the maximum concentration within a short time scale (3 h) suggesting a more rapid response to oxidative stress. AT was more resistant to UVR stress than the phytoflagellate species. Overall, our results show that UVR damage/repair balance involves the combined action of several internal factors in the cell.Original Abstract: La reduccion del ozono estratosferico antartico resulta en un incremento significativo de la radiacion ultravioleta B (UV-B, 280-320 nm) en la superficie del oceano. El principal objetivo de este trabajo fue un estudio de la respuesta a largo plazo al estres producido por UV-B y radiacion ultravioleta A (UV-A, 320-400 nm) en una especie de fitoflagelados (Asteromonas sp.). Dicha especie fue aislada de una comunidad subantartica natural del Canal Beagle y se analizo la tasa de crecimiento en escala diaria afectada por el dano oxidativo a lipidos, expresado como contenido de sustancias reactivas al acido tiobarbiturico (TBARS) y contenido de antioxidantes liposolubles. La tasa de crecimiento fue inhibida por la radiacion UV-B y UV-A durante la fase exponencial. Se observo un incremento marcado en el contenido de TBARS el primer dia del experimento, mostrando diferencias significativas entre algas sujetas a tratamientos de UV-B y UV-A, sugiriendo asi un alto dano a la membrana celular. Durante el segundo dia del experimento, los TBARS en el tratamiento de UV-A fueron mayores que aquellos en PAR (400-700 nm). La concentracion de TBARS decrecio al nivel del control PAR en el tercer dia, permaneciendo baja hasta el final del experimento. Las concentraciones de antioxidantes lipidicos ( alpha -tocopherol y beta -carotene) estuvieron retrasadas con respecto a variaciones en TBARS, presentando valores maximos al tercer dia de experimentacion. Esto coincidio con las concentraciones minimas de TBARS en todos los tratamientos. El contenido de ambos antioxidantes aumento significativamente en cultivos expuestos a UV-B y UV-A durante los dias 3 y 4. En especies antarticas (Asteromonas sp., AP y Thalassiosira sp., AT) alpha -tocopherol fue mas abundante que beta -carotene.