Seawater carbonate chemistry and effects of ocean acidification and rising sea surface temperatures on shallow-water benthic organisms in Antarctica

The seawater parameters oceanic pH and temperature were modified to near future projections for the western Antarctic Peninsula in microcosm experiments. Experiments included two crustose algae, the calcified coralline alga Clathromorphum obtectulum and the fleshy encrusting rhodophyte Hildenbrandia sp., and were run for six weeks. Treatments reflected near future ocean conditions under climate change predictions: increased temperature (3.5 °C × pH 8.1), increased pCO2 (1.5 °C × pH 7.8), combined factors (3.5 °C × pH 7.8), and ambient conditions (1.5 °C × pH 8.1). The physiological responses of the algae were evaluated through photosynthetic parameters (slope to saturation of photo centers (α), saturating irradiance (Ek), maximum electron transport rate (ETRmax), maximum quantum yield of photosystem II (Fv/Fm)), growth, chlorophyll a concentration, and for C. obtectulum calcium carbonate content and Mg/Ca ratio.