Effect of short-term immersion of Kappaphycus alvarezii (Doty) Doty in high nitrogen on the growth, nitrogen assimilation, carrageenan quality, and occurrence of “ice-ice” disease

Short-term immersion of Kappaphycus alvarezii (Doty) Doty in a high-nitrogen-containing medium was tested to increase growth, improve the quality of carrageenan, and decrease “ice-ice” disease occurrence. Tank-reared Kappaphycus were used as explants. Growth, nitrogen assimilation, carrageenan quality, and occurrence of ice-ice disease of enriched (E/N) K. alvarezii were determined. E/N and un-enriched (control) K. alvarezii were planted inside net cages in the sea. Nitrogen assimilation was monitored to determine if nitrogen was incorporated in the tissues after 12 h. Total thallus nitrogen of K. alvarezii doubled after immersion in high nitrogen. Growth rate and carrageenan yield of E/N K. alvarezii were significantly higher than those of the control. Gel strengths of E/N and the control were not significantly different. Ice-ice disease occurrence was significantly higher in the control than the enriched seaweeds. Short-term immersion of K. alvarezii in a high-nitrogen medium before outplanting increased growth rate and decreased the occurrence of “ice-ice”.Acknowledgement is due to the Australian Centre for International Agricultural Research (ACIAR SMAR/2008/025)