Co-Culturing Seaweed with Scallops Can Inhibit the Occurrence of Vibrio by Increasing Dissolved Oxygen and pH

Seaweeds are critically important for the maintenance of biodiversity in marine aquaculture ecosystems, as they can inhibit the growth of Vibrio. Here, we determined the optimal environmental parameters for co-culturing green macroalgae (Ulva pertusa) and red macroalgae (Gracilariopsis lemaneiformis) with Chinese scallop (Chlamys farreri) by measuring dissolved oxygen (DO), pH, and the strength of Vibrio inhibition under laboratory conditions and validating the effectiveness of this optimal co-culture system from the perspectives of nutrient levels, enzyme activities, and microbial diversity. The results show that co-culturing 30 g of seaweed and three scallops in 6 L of seawater with aeration in the dark (1.25 L min^-1, 12:12 h L:D) significantly decreased the number and abundance of Vibrio after 3 days. The activities of superoxide dismutase, catalase, pyruvate kinase, and lactate dehydrogenase in C. farreri were significantly higher, indicating that its immune defense and metabolism enhanced in this optimal co-culture system. High DO and pH levels significantly decreased the alpha diversity of microorganisms, and the abundance of pathogenic microorganisms decreased. The optimal co-culture system was effective for the control of vibriosis. Generally, our findings suggest that seaweeds could be used to enhance the aquaculture environment by conferring healthy and sustainable functions in the future.