Aquaculture effluent-based cultivation of Scenedesmus acuminatus and its application as an ingredient in tambaqui (Colossoma macropomum) diets

Abstract Aquaculture generates large volumes of nutrient-rich effluents that, if untreated, contribute to eutrophication. Microalgae-based phycoremediation is a sustainable strategy for recycling these effluents while producing high-nutritional-value biomass. This study evaluated the production performance, nutritional composition, and fatty acid profile of Scenedesmus acuminatus cultivated in aquaculture effluent and its inclusion in diets for juvenile tambaqui ( Colossoma macropomum ). Effluent from intensive Brycon amazonicus tanks was used as the sole nutrient source for cultivation in photobioreactors. The resulting biomass showed consistent production, high crude protein content (52.1%), relevant vitamin E levels (49.04 mg kg⁻ 1 ), and the presence of polyunsaturated fatty acids, including omega-3. The biomass was incorporated into five isonitrogenous (32.2% crude protein) and isoenergetic (17.22 MJ kg⁻ 1 ) diets: a control (SA0%) and four inclusion levels (SA1%, SA2%, SA3%, and SA5%). Juvenile tambaqui were fed the experimental diets for five weeks, and growth performance, hematological parameters, whole-body and fillet proximate composition, and fatty acid profiles were evaluated. Across all inclusion levels (1–5%), no significant differences were observed in survival, feed intake, growth performance, or whole-body and fillet proximate composition. Higher inclusion levels (SA3% and SA5%) were associated with increased thrombocyte and neutrophil counts, indicating immunomodulatory responses. The SA3% treatment resulted in a 45% higher omega-3 content in the fillet than the control; however, no statistical differences were detected among treatments ( p = 0.21), and the 5% inclusion level did not yield additional increases. These findings reinforce the feasibility of producing S . acuminatus biomass from aquaculture effluent and its use as a functional dietary ingredient, supporting circular bioeconomy strategies for sustainable aquaculture.