Seasonal variation in biomass and species composition of seaweeds stranded along Port Okha, northwest coast of India

Abstract

Port Okha coast, which is known for its luxuriant growth of a diverse assemblage of seaweeds on Saurashtra coast, is found to have abundant quantities of seaweeds being drifted and washed ashore every year. Studies conducted for quantifying the stranded seaweeds from May 2004 to April 2005 showed an average biomass value of 3.10 kg fresh wt/m2/month with maximum being 6.60 kg fresh wt/m2 in April. The stranded weeds constituted a total of 62 species during the entire study period. Of this, Rhodophyta ranked high with 26 species followed by Chlorophyta with 22 species and Phaeophyta with 14 species. The stranded seaweeds that were washed ashore provide valuable floristic information about the intertidal and near shore sub-tidal algae of the respective regions. Although natural senescence of seaweeds is one of the major factors, strong currents primarily forced by tides, also contribute to the uprooting and subsequent drifting of seaweeds on to the beach. This ultimately causes changes in floristic features of the existing algal beds.