This paper presents the results of a study on the impact of the effluent released by the soda ash industry on important red and brown macro algal species Gelidiella acerosa, Gracilaria corticata, Soleria robusta, Sargassum tenerrimum, Padina tetrastromatica in the tidal zone around Veraval, on the west coast of India, in the lowest low water tide of December 2003. The study examined the effect of effluent discharge on availability of biomass and percentage of phyco-colloids extraction such as agar, alginic acid and carrageen of these commercial seaweeds. (c) 2008 Elsevier B.V. All rights reserved.