Comparative Growth and Food Value of <i>Gracilaria verrucosa</i> , <i>Ulva lactuca</i> , and <i>Crassostrea belcheri</i> in Indoor Coculture: Implications for Sustainability

Gracilaria verrucosa and Ulva lactuca were cocultured with Crassostrea belcheri for 120 days in captivity while controls were the independent culture of these three species. The study assessed the water quality parameters, growth performance, proximate and biochemical composition of the organisms undergoing the different treatments. Moreover, they were compared with outdoor farmed seaweeds and oysters to assess their nutritional quality. Significant variations were seen in the growth rates of the two seaweeds, U. lactuca exhibiting the highest live weight gain (LWG) and specific growth rate (SGR) in coculture settings. The percentage of surviving oysters varied from 60% to 80% across experiments, with the fastest growth rates observed when cocultured with U. lactuca . The seaweeds’ moisture, ash, protein, carbohydrate, and fiber contents varied significantly, with U. lactuca (indoor) having the highest protein and carbohydrate content ( p &lt; 0.05) compared to U. lactuca (outdoor) and G. verrucosa (indoor and outdoor), and also recording the maximum total chlorophyl, carotenoids, and fucoxanthin. Significant variations were found in the fatty acid content of seaweed and oyster samples. Outdoor oyster samples had more omega‐3 fatty acids ( p &lt; 0.05) than indoor while the indoor seaweed samples had lower saturated fatty acids (SAFA), and higher polyunsaturated fatty acids (PUFA) than outdoor. U. lactuca grown indoors exhibited the highest levels of both essential amino acids (EAAs) and non‐essential amino acids (NEAAs). The study emphasizes how culture conditions affect the nutritional and biochemical profiles of seaweeds and oysters, and it offers indoor coculture as a potential substitute for inclement environmental conditions and as a backup strategy to enhance sustainable seaweed mariculture that allow for optimal growth and nutritional quality ensuring the maximum space utilization.