Photosynthetic pigments and color of wild Undaria pinnatifida for wakame production (Chubut, Patagonia Argentina)

The invasive brown seaweed Undaria pinnatifida was first recorded in the Southwest Atlantic in 1992 in Golfo Nuevo, northern Patagonia, Argentina. Since then, it has spread over most of the Argentine coast developing dense seasonal kelp beds. This seasonal biomass could be used for wakame production, for which the color is an important quality variable. The aim of this study was to determine the temporal and ontogenetic variations of pigments content and color of Undaria from Golfo Nuevo, and its relation to water temperature, irradiance, and nutrient concentration. Sporophytes present in five 1m2 quadrats were collected from a 2 m-depth hard bottom in five occasions between September and November 2018. Morphometric variables were measured in all the sporophytes collected (N = 200). Color (CIE Lab) and pigments (Chlorophyll a and c, and fucoxanthin) were measured on each juvenile and adult sporophyte. Color was also measured after boiling. Water temperature and irradiance were measured 70 cm above the bottom with a 10-minute frequency. Nitrate+nitrite, ammonium, and phosphate concentrations (mu M) were measured from surface seawater samples taken on each sampling date. Higher pigment content and better color parameters (lower L* and b*) were observed in adult sporophytes with thicker blades. In juvenile sporophytes with thin blades, L*and b* color parameters were strongly affected by pigment content. Temporal fluctuations of color parameters and pigment content were smooth and not significant. GLMs showed that variations in color parameters and pigments were mostly related to development and blade thickness, and at a lower extent, by nutrients and irradiance. We conclude that adult sporophytes have better color than juveniles for wakame production during the austral spring in the study area. However, further research would be necessary to analyze other quality parameters (e.g. hairs, wrinkles, and hardness) and their geographical variations.