Seasonal variations in growth, alginic acid and mannitol contents of Sargassum wightii and Turbinaria conoides from the Gulf of Mannar, India

Seasonal variations in growth, alginic acid and mannitol contents of Sargassum wightii and Turbinaria conoides growing in the Gulf of Mannar near Mandapam have been followed for a period of two and a half years from August 1965 to J a n u a r ~ 1'308. 3Iarl;ed seasonal changes occur in the growth of these two brown algae with a slow growth in the population up to July or -1ugust and a rapid growth from October to December when reproductive receptacles were noticed in both the species. Results obtained on the alginic acid and mannitol contents indicate that these two carbohydrates vary with tile seasonal growth behaviour of the two brown algae investigated. Yield of alginic acid is high during the peak growth and fruiting periods, Mannitol content is at its maximum in the early stages of the growth cycle from May to August and minimum after the initiation of the reproductive receptacles.