Short-term ecophysiological and biochemical responses of Cystoseira tamariscifolia and Ellisolandia elongata to environmental changes

Shortterm ecophysiological and biochemical responses of Cystoseira tamariscifolia and Ellisolandia elongata to changes in solar irradiance and nutrient levels were analyzed in situ in oligotrophic coastal waters by transferring macroalgae collected at 0.5 and 2.0 m depth and exposing them to 2 irradiance levels (100 and 70% of surface irradiance) and nutrient conditions (nutrient-enriched and non-enriched). Both species were affected by changes in irradiance and nutrient levels. Few interactive effects between these 2 physical stressors were found, suggesting major additive effects on both species. C. Tamariscifolia collected at 0.5 m and exposed to 70% irradiance had the highest maximal electron transport rate (ETR sub(max)), saturated irradiance (Ek sub(ETR)) and chl a content and the lowest antioxidant activity. Our results show rapid photophysiological responses of C. Tamariscifolia to variations in in situ irradiance and nutrient conditions, suggesting efficient photoacclimation to environmental changes. The responses of these macroalgae to nutrient enrichment indicate oligotrophic conditions at the study site and environmental stress.