Growth, phytochemicals, and optimal timing of planting Gracilariopsis persica: an economic red seaweed

Abstract

A culture system for the commercial agarophyte seaweed Gracilariopsis persica has been developed, using long-line rope method in outdoor condition. Several environmental parameters of seawater at the cultivation site were recorded monthly over a year (December 2014 to November 2015). Relative growth rate (RGR) and its correlation with environmental parameters was investigated using Pearson correlations test. Phytochemical composition (moisture content, ash, protein, and lipid content) and agar yield quantity and quality (FTIR analysis of agar product) were studied during the cultivation period. We could grow the species only in 4 months of the year, December (2014) to March (2015), in outdoor conditions. The highest RGR (9.42% day−1) was obtained in February which was significantly different from the other months of growing period. Temperature, followed by nitrate and salinity, had significant effects on growth. RGR showed positive correlation with oxygen concentration and orthophosphate and negative correlations with temperature (r = −0.657), salinity (r = −0.607), and nitrate (r = −0.635). The yield of agar ranged from 26.7 to 33.7% with an average of 31.72% ± 0.18. FTIR analyses of agar product from Gp. persica showed similar FTIR patterns which mean that environmental conditions had no significant effect on the chemical structure. The range of moisture content (91.40–90.20%), ash (23–41% d.w.), protein (3.57–4.11% d.w.), and lipid (1.06–1.70% d.w.) showed the slight monthly significant difference in biochemical composition in the cultivated seaweed. These results indicated that Gp. persica can be successfully cultivated in the study area.