Climate change effects on phytoplankton from coastal Antarctica: a fatty acid approach.

ANTACLI JULIETA; HERNANDO MARCELO ; DE TROCH MARLEEN; MALANGA GABRIELA; MENDIOLAR MANUELA; VARELA DIANA; ANTONI JULIETA; ALMANDOZ GASTON; HERNÁNDEZ DANIEL; GIMÉNEZ DIEGO; SAHADE RICARDO; SCHLOSS IRENE

Mar del Plata

Congreso; XVIII Congreso Latinoamericano de Ciencias del Mar-COLACMAR 2019. Asociación Latinoamericana de Investigadores en Ciencias del Mar-ALICMAR; 2019

Marine plankton use different strategies to cope with ocean warming and reduced salinity from glacial melting (1). We studied these effects on the physiology of natural phytoplankton assemblages from Potter Cove (25 de Mayo Island, Antarctica) in the 2016 summer during 7 days in outdoor microcosms. A 4°C increase in seawater temperature (T+) and a 4 psu decrease in salinity (S-) from ambient values were studied using the following treatments: control (S0T0), S-T0, S0T+, and S-T+. Changes in fatty acid and particulate carbon content (C), and the balance between lipid damage and lipid soluble antioxidants (α-tocopherol) were analyzed. Saturated fatty acid (SFA) concentrations were higher than polyunsaturated (PUFA) and monounsaturated (MUFA) FAs in all treatments. However, a significant increase in the unsaturated (UFA)/SFA ratio was observed on day 3 in S0T+. A significant increase in lipid damage was measured under S-T+ but only on day 1, and it decreased when α-tocopherol concentrations increased, which resulted in C biomass accumulation under T+. Natural phytoplankton assemblages were dominated by the sub-Antarctic diatoms Chaetoceros and Shionodiscus. Noteworthy, under S-T0, with constant lipid damage due to stress, small phytoflagellates became dominant at the end of the experiment, contrasting with the sub-Antarctic diatoms still dominating in other treatments. This study suggests that although sub-Antarctic species are adapted to T+ conditions, they are still affected by salinity stress, which they partially compensate by adjusting lipid composition and increasing α-tocopherol production.