Composition and function of biofilm microbial communities reveal high efficiency potential in carbohydrate metabolism in the mariculture.

Biofilms on composite carriers may contribute to organic matter transformation in mariculture effluents, but the taxa and carbon-metabolic functions underlying this process remain unclear. This study employed metagenomic sequencing and functional annotation to comprehensively analyze the microbial composition and metabolic potential involved in glycoside hydrolase (GH), glycolysis, and the tricarboxylic acid (TCA) cycle in biofilms, revealing the functional characteristics of microbial communities in carbon metabolism. The results showed high microbial diversity in various carbon metabolism pathways, with Bacteroidota, Proteobacteria, and Planctomycetota being the dominant phyla, and Flavobacteriales and Planctomycetales being the predominant orders across all metabolic pathways. Functional analysis indicated that key enzymes involved in polysaccharide hydrolysis, glycolysis, and the TCA cycle exhibited high abundance. Core functional genes included polysaccharide hydrolases (GH33, GH109), glycolytic enzymes (glyceraldehyde-3-phosphate dehydrogenase, phosphofructokinase), and TCA cycle enzymes (succinate dehydrogenase, pyruvate dehydrogenase). These profiles suggest that carrier-associated biofilm communities harbor coordinated genetic potential for carbohydrate depolymerization and downstream central carbon metabolism in mariculture effluents. This study offers theoretical and practical guidance for developing efficient and sustainable biofilm-based wastewater treatment systems.