This study delves into the nutraceutical potential of microalgae in brackishwater aquaculture, with a focus on a case study conducted in the Muttukadu estuary, Tamil Nadu, India. The research involved the collection, identification, culture standardization, nutrient profiling, antioxidant and antibacterial properties of seven microalgal species in the brackishwater ecosystem, including Thalassiosira weissflogiiChaetoceros gracilisNannochloropsis oculataChlorella marina, Tetraselmis sp, Isochrysis galbana and Arthrospira maxima. The growth kinetics analysis highlighted N. oculata and C. marina with an extended log phase and significantly higher growth rates. Proximate analysis revealed the highest protein content (62.46 ± 3.45%) in A. maximaI. galbana showed significantly higher lipid content (33.08 ± 2.18%), while T. weissflogii had 20.11 ± 1.02%. Fatty acid profiling identified the highest percentage of polyunsaturated fatty acids (69.51%) in A. maxima, followed by Tetraselmis sp (56.32%). Methanolic extracts from C. marina and T. weissflogii displayed notably higher total phenolic content. A. maxima exhibited the highest total antioxidant activity, and C-Phycocyanin (CPC) extracts showed the highest inhibition zones against pathogenic bacteria. This study underscored the diversity of commercially important microalgal species in the tropical estuarine brackishwater ecosystem. The nutrient composition analysis emphasized the abundance of essential macronutrients, micronutrients, vitamins, and bioactive compounds. These findings contribute to understanding microalgae’s nutraceutical potential in brackishwater aquaculture, suggesting their suitability for large-scale cultivation and utilization in aquaculture and other food-producing industries. Moreover, the bioactive compounds present in these microalgae offer opportunities for developing novel nutraceutical formulations with potential health benefits.

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