Effects of ocean acidification on the levels of primary and secondary metabolites in the brown macroalga Sargassum vulgare at different time scales

Highlights

Sargassum vulgare growing at CO2 vents was compared with those growing at control site.
S. vulgare from control site was transplanted to CO2 vents for 2 weeks.
• In short-term responses, S. vulgare showed increased level of sugars, PUFAs, and EAAs.
• Natural population at vents showed decreased sugars, PUFAs, phenols, and increased EAAs.
• Nutritional values of algae will decrease under acidification in long time scale.

Abstract

Most of the studies regarding the impact of ocean acidification on macroalgae have been carried out for short-term periods, in controlled laboratory conditions, thus hampering the possibility to scale up the effects on long-term. In the present study, the volcanic CO2 vents off Ischia Island were used as a natural laboratory to investigate the metabolic response of the brown alga Sargassum vulgare to acidification at different time scales. For long-term effects, algal populations naturally growing at acidified and control sites were compared. For short-term responses, in situ reciprocal transplants from control to acidified site and vice-versa were performed. Changes in the levels of sugars, fatty acids (FAs), amino acids (AAs), antioxidants, and phenolic compounds were examined. Our main finding includes variable metabolic response of this alga at different time scales to natural acidification. The levels of sugars, FAs, and some secondary metabolites were lower in the natural population at the acidified site, whereas the majority of AAs were higher than those detected in thalli growing at control site. Moreover, in algae transplanted from control to acidified site, soluble sugars (glucose and mannose), majority of AAs, and FAs increased in comparison to control plants transplanted within the same site. The differences in the response of the macroalga suggest that the metabolic changes observed in transplants may be due to acclimation that supports algae to cope with acidification, thus leading to adaptation to lowered pH in long time scale.

Graphical abstract

Unlabelled Image

Kumar A., AbdElgawad H., Castellano I., Selim S., Beemster G. T. S., Asard H., Buia M. C. & Palumbo A., 2018. Effects of ocean acidification on the levels of primary and secondary metabolites in the brown macroalga Sargassum vulgare at different time scales. Science of the Total Environment 643: 946–956. Article (subscription required).


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