In vitro assays with Kappaphycus alvarezii for the bioremediation of coastal eutrophic systems in Southeast Brazil

Abstract

Abstract The commercial alga Kappaphycus alvarezii (Doty) L.M.Liao 1996 may constitute a good bioremediator for eutrophicated coastal environments. In the present research, the ability of K. alvarezii to remove nutrients from the water was tested via in vitro experiments under various conditions. Cultivated K. alvarezii samples were obtained from commercial aquaculture in Angra dos Reis, Brazil, together with large volumes of water from the same area and Rodrigo de Freitas Lagoon, Rio de Janeiro, Brazil. Eight experimental sets were prepared with variable concentrations of nutrients, and pre-weighed pieces of algae, subjected to artificial illumination. The physical-chemical parameters were continuously monitored. Water samples were periodically analyzed for ammonium, nitrite, nitrate, and phosphate. Algal samples were collected at the end of the experiment to quantify biomass growth/decay, nitrogen and phosphorus tissue contents. The ammonium concentration in the water decreased due to preferential consumption of this nutrient by the algae, as well as oxidation. The algae were able to incorporate nutrients in their tissues; however, they were not able to promote a reduction in dissolved concentrations. Nutrient removal rates were elevated and seemed to occur in microcosms at the very beginning of the experiments, but release was observed in the end. However, phosphorus removal was attained in the microcosms that did not receive artificial fertilizers. It was concluded that the use of K. alvarezii as a bioremediator in coastal lagoons is possible, but more complex in vitro and in situ experiments are still necessary for a better understanding of removal processes.