Estudo da influência da temperatura e da fonte de água no crescimento e fisiologia da Macroalga Kappaphycus alvarezii cultivada em laboratório

Abstract

The cultivation of marine macroalgae has been expanding due to the socioeconomic and environmental relevance of the activity. Kappaphycus alvarezii is currently the fifth most cultivated macroalgae worldwide, exploited mainly for the extraction of carrageenan, a hydrocolloid with applications in the food, pharmaceutical, and cosmetic industries. Fluctuations in production, increased cases of bleaching and degradation of K. alvarezii thalli have been reported in several tropical countries that cultivate this macroalga, often associated with thermal stress. This study aimed to evaluate the effect of different temperatures and water source on the growth and physiology of the macroalga K. alvarezii in the laboratory. The experiment was conducted in three different cultivation cycles (each temperature treatment corresponds to a cycle) where temperatures of 20°C, 25°C and 28°C were tested, respectively, and water from Costa do Sol and Ilha de Inhaca was tested at each temperature. Each cultivation cycle lasted 15 days. During laboratory cultivation, the physicochemical parameters of the water were monitored, and at the end of each cycle, growth rates and concentrations of photosynthetic pigments (carotenoids and phycoerythrin) were determined. The results showed that K.alvarezii had greater growth at 20°C (0.95% day⁻¹ to 1.41% day⁻¹) compared to those cultivated at 25°C and 28°C (0.64% day⁻¹ to 0.78% day⁻¹ and 0.66% day⁻¹ to 0.68% day⁻¹, respectively) and had a higher growth rate in the water from Costa do Sol. The macroalgae cultivated in the water from Costa do Sol at 28°C showed partial bleaching of the thallus, and the macroalgae cultivated at 25°C were those that had the least color changes. Carotenoid production increased with increasing temperature in macroalgae cultivated in the water of Costa do Sol with 0.13 𝜇𝑔 𝑔 −1 , 0.81 𝜇𝑔 𝑔 −1 and 1.16 𝜇𝑔 𝑔 −1 at 20°C, 25°C and 28°C, respectively, and in macroalgae cultivated in the water of Ilha de Inhaca it was higher at 25°C (0.85 𝜇𝑔 𝑔 −1 ), and lower at 25°C and 28°C (0.20 𝜇𝑔 𝑔 −1 and 0.27 𝜇𝑔 𝑔 −1 , respectively). Phycoerythrin production increased with increasing temperature and was higher in macroalgae cultivated in the water of Inhaca Island. This study suggests that K. alvarezii grows ideally at 20°C in the water of Costa do Sol and increases the production of photosynthetic pigments with increasing temperature, performing better in the water of Inhaca Island.(TRADUÇAO NOSSA)