POUVOIR EPURATEUR ET CROISSANCE DE LA RHODOPHYTE GRACILARIA BURSA-PASTORIS ET LA CHLOROPHYTE ULVA sp. DANS LES EFFLUENTS PISCICOLES

Abstract

Aquaculture releases large amount of nutrients, generated by cultured organisms into aquatic ecosystems. For their growth, seaweeds are efficient in reducing nutrients and at the same time provide extra income when species of economic importance are used. This study aims to compare the efficiency of the red algae Gracilaria bursa-pastoris and the green algae Ulva sp. in the removal of nutrients from fish culture effluents and the production of useful algal biomass. The study on growth and biofiltration capacity of the alga was conducted under laboratory and lasted two weeks. The results showed that in the first height hours, the two algae reduced significantly the concentrations of the analyzed nutrients (NH₄⁺, NO₃^- et PO₄³⁺). However, Ulva sp. was faster to absorb the maximum of nutrients. At the same time, both algae increased their biomass and the specific growth rate of G. bursa-pastoris and Ulva sp. were 1.97 and 2.74%d^-1 respectively. The results obtained in this study indicated that both algae can be used in aquaculture as a biofilter and the produced algal biomass offers alternatives for biotechnology aspects.