In an investigation published in the journal Biochar X, researchers Bing Chen, Junru Hu, Kai Peng, Wen Huang, Jinhong Li, Mulian Wei, Zhihua Zeng, Dongxu Xing, Bing Fu, Junming Cao, Hongxia Zhao, Xiang Li, and Hailong Wang examined how incorporating biochar derived from carbonized mulberry branches into fish feed impacts the farming environment and physiological development of largemouth bass. The team focused on addressing the dual complications of industrial aquaculture, where intensive stocking configurations frequently result in systemic fish health disorders and severe water pollution caused by unabsorbed dietary nutrients. Over a forty-two day feeding trial, juvenile fish were given experimental diets mixed with varying concentrations of biochar to evaluate subsequent physiological and environmental alterations. The data revealed that while the carbonaceous supplement did not induce significant differences in gross growth parameters like weight gain or feed conversion ratios across the groups, it initiated profound positive changes inside the digestive tracts of the fish and in the overall cleanliness of the rearing tanks.

The primary physiological findings highlights a remarkable boost in the digestive and metabolic capacity of the largemouth bass. Fish that received twenty and forty grams per kilogram of dietary biochar showed a substantial enhancement in pancreatic protease and amylase activities, indicating a sharper capacity for processing essential proteins and carbohydrates. Concurrently, low-dose supplementation at ten grams per kilogram dramatically strengthened the physical defenses and immune status of the gut by upregulating key anti-inflammatory and tight junction protein genes. This molecular shift was accompanied by a noticeable expansion in the diversity and abundance of beneficial gut microbes. The inclusion of biochar created a specialized structural niche that selectively multiplied helpful microbial groups while lowering the ratio of energy-absorbing bacteria, which ultimately points to improved fat metabolism and streamlined energy assimilation from the ingested pellets.

Beyond general structural upgrades to the gut, the dietary supplement acted as an effective biological shield against typical aquatic pathogens. The relative abundance of problematic bacterial genera, such as Plesiomonas and Mycoplasma, dropped sharply in the biochar-fed cohorts. Because these specific microbes are known to provoke severe enteritis and compromise standard immunity in aquatic species, their reduction underscores the capacity of biochar to create a balanced, low-stress internal environment. Predictive functional mapping further confirmed that the microbial communities in the optimized biochar groups were highly oriented toward active carbohydrate, amino acid, and foreign substance biodegradation pathways, contrasting with the control group where microflora remained primarily occupied with basic cell motility and membrane transport.

Simultaneously, the research group documented striking improvements in external water quality, resolving a major bottleneck in recirculating aquaculture setups. Fish continuously excrete nitrogenous wastes that quickly break down into toxic elements, but the groups fed ten and twenty grams per kilogram of biochar saw massive drops in ambient pollution. By the final day of the experiment, ammonia nitrogen concentrations plunged by sixty point seven percent and forty-nine point three percent for the moderate-dose treatments compared to the bare control setup. Nitrite nitrogen levels dropped even more drastically, showing a ninety-one point seven eight percent reduction in the ten-gram group. These impressive numbers stem from the high surface area and porous nature of the excreted biochar, which binds directly to nitrogenous molecules and creates an ideal breeding ground for beneficial, waste-consuming nitrifying bacteria in the water.

However, the manuscript also establishes a clear threshold for safe administration, showing that excessive doses introduce physiological drawbacks. Fish fed the highest concentration of forty grams per kilogram suffered from a significant decline in both body plumpness and key fat-digesting enzyme performance, likely because the dense carbon matrix ended up trapping vital lipids and vitamins before the fish could absorb them. This heavy dose also scattered the normal community structure of the gut microbiome, sparking unwanted intestinal inflammation and elevated cellular stress markers. Consequently, the investigators concluded that keeping inclusion levels strictly between ten and twenty grams per kilogram delivers the ideal balance, ensuring robust internal health for the largemouth bass while actively maintaining a clean, sustainable aquaculture ecosystem.

Source: Chen, B., Hu, J., Peng, K., Huang, W., Li, J., Wei, M., Zeng, Z., Xing, D., Fu, B., Cao, J., Zhao, H., Li, X., & Wang, H. (2026). Dietary mulberry branch biochar improves intestinal health and water quality in largemouth bass (Micropterus salmoides) aquaculture. Biochar X, 2, 2014.