Seasonal variation in chemical constituents of certain brown seaweeds and seawater from Saurashtra Coast: II. Manganese, zinc, copper, nickel, cobalt and molybdenum

Abstract

Mn, Zn, Cu, Ni, Co and Mo contents have been estimated in seawater and three brown seaweeds viz., Cystoseira indica (Thivy et Doshi) Mairh, Sargassum johnstonii Setchell and Gardner and S. Tenerrimum J. Ag. from Porbandar and Okha reefs of Saurashtra coast collected during October 1982 to September 1983. During the high biomass period a depletion in the metal content was observed in both Porbandar and Okha waters. Seasonal variations in trace metal content of seaweeds was found to be more related to phenological stages than to the ambient metal concentration, if the latter is not limiting the seaweed growth. The individual element accumulation throughout their life cycle was in the order of Mn Zn Cu Ni Co Mo. Cumulative concentration factors (ratio between the total concentration of a metal in a seaweed and that in seawater during a particular period) in seaweeds exhibit distinct seasonal variations. A rapid increase in early growth to rapid biomass period is followed by more or less steady increase in other stages with age.