EFFECTS OF ENVIRONMENTAL-FACTORS ON CARRAGEENAN FROM GYMNOGONGRUS-GRIFFITHSIAE (GIGARTINALES, RHODOPHYTA)

The effects of environmental factors on substratum coverage, thallus length, production of iota carrageenan and gelling behavior were investigated in field populations of the red alga Gymnogongrus griffithsiae (Turner) Martius. Irradiance and water temperature affected thallus substratum coverage and water gel strength of the carrageenan. The significant monthly differences in thallus length, carrageenan content and carrageenan gelling properties were not attributable to seasonal variations in irradiance and water temperature. The effect of temperature and N loading on biomass productivity, carrageenan yield and gelling characteristics were also investigated using cultures. N-enriched cultures showed decreased gel yields, higher viscosities and higher water gel strengths in the carrageenans extracted from these cultures. Milk reactivity tests were correlated with thallus nitrogen and water dessert gel strength, but neither culture temperature nor N loading showed a significant effect. The field and culture studies indicate how temperature, irradiance and N availability affect growth and hydrocolloid production.