Assessment of some agarophytes from the coastal areas of Iloilo, Philippines. II. Seasonal variations in the agar quality of Gracilaria changii, Gracilaria manilaensis and Gracilariopsis bailinae (Gracilariales, Rhodophyta)

Abstract

Three species of agarophytes (Gracilaria changii, G. manilaensis and Gracilariopsis bailinae) collected along the mud flats of Iloilo were investigated to determine the monthly variation in agar yield (%), gel strength (g cm^-2), gelling and melting temperatures (°C) and sulfate content (µg mg^-1). Results show that Gracilariopsis bailinae collected at Zarraga gave a higher gel strength (784 g cm^-2) than that collected at Estancia (637 g cm^-2), however, the latter gave a higher agar yield (22%). A year-round source of agar was demonstrated in G. bailinae in both places while Gracilaria changii (January to June) and G. manilaensis (April to June) were seasonal. Higher agar yield and gel strength were measured from G. changii than in G. manilaensis. Gracilariopsis bailinae showed agar qualities superior to those of the two other species, hence it is a good species to harvest and develop for mariculture and consequently for agar manufacture.