Probiotic effects of Marichromatium gracile DH-1 on growth, immunity, and water quality in juvenile seahorses: A potential strategy for sustainable aquaculture

This study examines the probiotic effects of Marichromatium gracile DH-1 supplementation on the growth and health of juvenile Hippocampus abdominalis in aquaculture. Over 40 days, juvenile seahorses were exposed to varying concentrations of strain DH-1 (25, 50, and 100 ppm) in aquaculture water. Results showed significant improvements in growth performance, with enhanced body length, weight gain, specific growth rate (SGR), and condition factor (CF) in the experimental groups compared to the control. The high-concentration group exhibited the best survival rate (12%) compared to the control (1.33%). Additionally, DH-1 supplementation promoted intestinal enzyme activities, particularly α-amylase and total protease, and increased antioxidant enzyme activity, including catalase (CAT) and glutathione peroxidase (GPx). The microbial community of the intestinal microbiota showed increased diversity and beneficial taxa, with reductions in harmful bacteria. DH-1 supplementation also improved water quality by reducing ammonia nitrogen and nitrite levels while increasing dissolved oxygen. These findings suggest that M. gracile DH-1 can enhance seahorse growth, immunity, and water quality, providing a potential probiotic strategy for sustainable aquaculture. Future studies should explore the mechanisms of interaction between DH-1 and its host, and its long-term effects on health and disease resistance.