The removal process of zinc from an aqueous solution illustrated a good biosorption of metal by both algal fresh materials. However, the highest removal percentage of zinc by P. capillacea was found to be greater than that by S. hornschuchii. The removal of zinc by P. capillacea and S. hornschuchii increased with increase in contact time up to 3 and 5 hours, respectively. It decreased by very slight rate within 4–12 hours for P. capillacea and within 6–12 hours for S. hornschuchii. This study evaluated the effect of zinc on growth, amino acids, fatty acids and protein contents of Pterocladia capillacea and Sargassum hornschuchii  .In this investigation P. capillacea tolerates higher concentrations of heavy metals as compared to S.hornschuchii . Exposure of P. capillacea to zinc decreased all amino acids except tyrosine, phenylalanine and proline which increased. All amino acids of S.hornschuchii  increased by exposure to zinc except glycine, alanine, valine, leucine, isoleucine, phenylalanine and methionine, which decreased. The protein content of P. capillacea was inhibited by zinc, while percentage of protein content of S.hornschuchii increased more than three times by exposure to zinc. All fatty acids of P. capillacea increased by exposure to zinc except C_16:1, which decreased and C_11:0, C _20:0 and C_17:1, which disappeared and C_{18:3 ­} and C_20:5, which appeared. Exposure of S.hornschuchii to zinc causes the increase of the contents of all fatty acids except C_6:0, C_10:0, C_18:0 and C_18:2, which decreased, C_23:0 and C_20:3, which appeared. Concerning the ultrastructure of P. capillacea grown in zinc solution for hours, it showed destructive irregularity of cell wall, disordering of cell inclusions, appearance of vacuoles and aggregation of cell components in a dense black manner inside the cell, while examination of S. hornschuchiiultra-structure with zinc showed destructive change in thyllakoids arrangement and slightly deviation of protoplast from the cell wall.