Melt water and oxidative stress in coastal Antarctic phytoplankton.

HERNANDO M; SCHLOSS I.; MALANGA G.; PUNTARULO S.; FERREYRA G.

Cordoba, Argentina

Workshop; 1st IMCOAST Workshop and Meeting; 2010

Melt water and oxidative stress in coastal Antarctic phytoplankton Marcelo Hernando, Irene Schloss, Gabriela Malanga, Susana Puntarulo,  Gustavo Ferreyra (University of Buenos Aires, PRALIB and Institute of Marine Sciences Rimouski, Canada)    mphernando09@hotmail.com Increased ice melting due to global climate warming drives changes in salinity in  Antarctic coastal surface waters. This might expose phytoplankton cells to osmotic stress, which leads to the production of reactive oxygen species (ROS) and lipid peroxidation. Different phytoplankton groups react differently to this stress. Here we analysed the cell content of ROS, TBARS, which are indicators of free radical formation and accelerated lipid peroxidation, and liposoluble antioxidants in two different phytoplankton assemblages, one dominated by the diatom Porosira glacialis and the other one by picoplankton which was experimentally exposed to different salinties.The treatment mimicks variable salinities fronting melting glaciers. ROS concentration in picoplankton was significantly lower than in the diatom, both before and after exposure to osmotic stress, while soluble antioxidants (a-tocopherol y b-carothenes) concentrations were higher in picoplankton than in P. glacialis. Oxygen consumption was measured in both isolates in the dark, and we observed a higher consumption in P. glaciales exposed to low salinity compared with picoplankton maintained at the same salinity. Our results suggest a species specific response to osmotic stress which could affect the carbon cycle in coastal Antarctic phytoplankton.