This study aimed to obtain biosorbents based on seaweed, which can be used to remove heavy metal cations present in aqueous systems. Evaluate the ability to remove cations by natural algae and chemically modified algae. Taxonomic and chemical characterization of these algae was carried out and then two stages of biosorption tests where the first with the purpose of estimating the biosorption potential of the metal Co (II) and the second with the intention of understanding the variables involved in the biosorption process. of the chosen seaweed. The concentration of elements and / or chemical substances in macroalgae will serve as indicators of pollutants and probably new contributions to science, since, to date, no study on the topic has been carried out in the metropolitan region of Baixada Santista. Through this information, one can have subsidies for long-term ecological studies in the sense of local preservation. Among the observations made, it was found that the macroalgae bioaccumulated many substances such as calcium (Ca), chlorine (Cl) and Silicon (Si) in high concentrations as shown in the graphs, but nothing that could harm the fauna, flora and fauna. population that happens to have contact with water, other sampling will be carried out in different places in order to have different results. In addition to serving as bioaccumulators for heavy metals as shown in the graphs, they also served as a shelter for small animals, found several times. It is believed that with the continuation of the project we will have rich information about the importance of macroalgae for the environment, helping the recovery of seas and oceans where anthropic action may have occurred.