Improved growth performance of Gracilariopsis heteroclada via short-term nitrogen enrichment

Abstract

This study examined the effect of short-term nitrogen (N) enrichment on Gracilariopsis heteroclada growth and agar quality. Planting materials were soaked in different concentrations of ammonium chloride (NH₄Cl) for 6 h. Total thallus N content was highest in Gp. heteroclada enriched in 300 mg l^-1 NH₄Cl. Growth experiments showed that this enrichment treatment (300 mg l^-1 NH₄Cl for 6 h) increased the growth of Gp. heteroclada (4.22±0.09% day^-1) compared with the control (3.68±0.12% day^-1). Pond culture using enriched Gp. heteroclada resulted in high growth rates (6.14±0.50% day^-1). No epiphyte growth was observed during either the growth experiment or the pond culture. There were no significant differences between the agar yields of the enriched (3.65±0.36%) or control (3.78±0.18%) Gp. heteroclada. Additionally, no significant differences were detected when the gel strength of the enriched (611±22 g cm^-2) and control (587±11 g cm^-2) Gp. heteroclada were compared. The results suggest that the short-term N enrichment method could be an alternative culture strategy to increase Gp. heteroclada production and lower farming costs.