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

Abstract

Monthly biomass (g dwt m^-2) of Gracilaria changii, G. manilaensis and Gracilariopsis bailinae collected in four different coastal areas of Iloilo, Philippines showed significant differences. Gracilaria changii (3.0-32.4 gm^-2) and G. manilaensis (8.9-35.7 gm^-2) were present only for six and three months respectively during the dry season. Gracilariopsis bailinae was present year-round at both sites, however, its abundance was not uniform, being abundant during the wet season in Estancia (13.4-119.3 gm^-2) and during the dry season in Zarraga (6.9-43.5 gm^-2). Except for rainfall and level of phosphate, all environmental factors (temperature, salinity, pH, turbidity, NO₂-N and NH₂-N) showed insignificant relationship with the biomass of each species.