Growth of red alga Gracilariopsis persica (Rhodophyceae) in desalination pools of Qeshm Island

Gracilariopsis persica is one of the most abundant red algae distributed in Persian Gulf, despite increasing use in medicine as a major source for natural biomaterials and bioactive compounds in recent years, the researches on growth parameters of this alga remains limited. The main aim of this research was to study the favorable conditions for G. persica growth. Also it was to find the suitable primary storage density for the establishment of algal thallus in the appropriate depth which causes increase in biomass in the concrete pool of Qeshm Island. Tall of G. persica were grown for 45 days on polyethylene ropes with primary storage weight of 100 and 200 gm-1 in two depths of 1 and 2 m. The effect of environmental factors such as temperature, salinity, pH, and nutrient absorption were investigated for different treatments. Growth rate during the cultivation period increased for both densities of 100 g and 200 g of G. persica at first but decreased then along with the time till sixth week. The highest growth rate (percentage of increase in fresh weight d-1) was obtained for the density of 100 g in 1 m depth in 45 days and the lowest growth rate was observed for the density of 200 g in 2 m depth. Relative growth rate (RGR) was measured weekly based on the changes in fresh weight and showed the highest efficiency in 1 m depth and 100 g density (15.47% d-1). The results showed that nutrients, especially those containing nitrogen and affecting algae growth at low depth, were inversely related (Kendall and Spearman negative correlation coefficients) to growth rate at 1 m depth. At depth 2 m, alga growth showed negative correlation with NO3- and NO2-. Findings provide novel evidence concerning growth and culturing conditions of G. persica, which can aid in the development of cultivating protocols for commercial agar production by this alga.