Short-term effects of increasing CO2, nitrate and temperature on three Mediterranean macroalgae: biochemical composition

Short-term effects of increasing pCO2; 380 ppm (LC) vs. 700 ppm (HC); at differentnitrogen levels; 5 μM nitrate (LN) vs. 50 μM (HN); on the contents of protein, mycosporine-likeamino acids (MAAs), phenolic compounds and total fatty acids, antioxidant activity, calcificationand C:N ratios were analyzed in 3 eulittoral Mediterranean macroalgae with different bio-opticalcharacteristics and carbon assimilation efficiencies: Cystoseira tamariscifolia (Heterokontophyta),Ulva rigida (Chlorophyta) and Ellisolandia elongata (Rhodophyta). After acclimation to differentpCO2 and nitrogen conditions for 6 d, the algae were subjected to a 4°C temperature increase for3 d. Increasing temperature and pCO2 produced alterations in the biochemical composition of the3 macroalgae. Short-term variations of protein levels were observed in U. rigida, with clearlydecreased values in the HCLN treatment. In C. tamariscifolia, protein decreased after the temper-ature increase but only under LC. The interaction of temperature and N affected phenolic com-pounds only in U. rigida and the content of MAAs in E. elongata. The functional patterns of the3 macroalgae in response to the pCO2, nitrogen and temperature regimes may be explained interms of their bio-optical characteristics and antioxidant activity. The vulnerability and acclima-tion of the 3 species to the expected variations of climate change factors are discussed.