The use of soil probiotics in aquaculture is a natural solution to enhance bottom pond soil and water quality, boost survival rates, and improve growth of cultured species. However, selecting the right strains of Bacillus spores to be used as commercial microbial agents remains a challenging task.
The aim of this study was to investigate the prospective effect of magnetic field on spore germination of two popular Bacillus probiotics for aquaculture as water additives. The result shows that the bacterial count increased within 6 h after the magnetic field exposure reaching its maximum at 36 h.
1. Preventing the Introduction of Sediment and Nutrients
Probiotics, when administrated directly in the water, are able to promote an improvement of water and bottom pond quality by avoiding the accumulation of organic wastes. They also help to eliminate the pathogenic bacteria by preventing them from absorption of nutrients, which is why their application in aquaculture prevents diseases and improves health conditions for fish and shrimp.
Sediment often carries animal and plant wastes, as well as chemicals such as pesticides that can be toxic to aquatic plants and animals. These pollutants can also cause water to become unusable. For example, excessive phosphorus can stimulate algae growth that decreases dissolved oxygen in lakes, leading to fish kills and reduced aesthetic and recreational value for the lake or stream. Phosphorus can be introduced to a waterbody from fertilizers, manure, and lawn chemicals or from other agricultural or livestock activities.
In addition, a blend of Bacillus probiotics has been shown to be able to maintain the levels of DO in the water at optimum values, which is essential for aquaculture (Hura et al. 2018). Probiotics can also reduce NH3 through their degradation. In fact, a significant negative correlation of NH3 with TVC and pH was observed in control ponds while in ponds treated with probiotics this relationship was inverted, with a positive correlation of NH3 with both of these parameters.
2. Increasing the Biodiversity of the Water
The use of probiotics in aquaculture can improve the health and welfare of aquatic organisms, as well as protect the environment by decreasing organic pollution (Verschuere & Co). In the study, Bacillus licheniformis probiotics was added to the diet of Nile tilapia and increased feed conversion rate (FCR), body weight gain (BWG) and resistance to challenge infections. Furthermore, it increased the concentration of insulin-like growth factor I (IGF I) in fish and stimulated the expression of antioxidative enzymes like superoxide dismutase, catalase and glutathione peroxidase to increase stress tolerance of the fish.
Another important benefit of probiotics is their ability to enhance the biodiversity of the water in aquaculture ponds, as they can significantly reduce the amount of organic waste by breaking down nitrate and ammonium into nitrogen gas. The bacterium also transforms organic carbon into inorganic carbon and oxygen.
The bacillus bacteria also eliminate contaminants in the water by using different mechanisms to destroy them, such as synthesis of bacteriocins, siderophores, lysozyme, protease and hydrogen peroxide as well as pH alterations. The researchers concluded that, although most studies of bacillus probiotics are oriented towards nutrition, more research needs to be conducted on the ways bacterial probiotics can mitigate water quality problems in aquaculture. A recent paper in Aquaculture Reports summarizes various studies that have proven that deploying bacillus directly into the aquaculture water can improve key water quality parameters such as transparency and nitrogen load.
3. Reducing the Emissions of Volatile Organic Compounds (VOCs)
The overgrowth of opportunistic microorganisms in aquaculture and mycotoxigenic fungi that spoil feeds have become serious problems for industrial fish cultivation. The result is a decrease in the general condition of farmed fish, the development of diseases complicated by antibiotic resistance and an increase in the use of medications and antibiotics in aquaculture.
Probiotics can prevent the spread of pathogens and reduce the need to add antibiotics in aquaculture. They do this by releasing spores and metabolites that inhibit the growth of the pathogens. This can also help to boost the immune system of farmed fish, which means that they can fight off the infection without needing antibiotics.
In addition, probiotics can also help to reduce the amount of organic waste in the water. This is because they break down the organic wastes into carbon dioxide and other substances, which can then be recycled in the ecosystem. This also helps to lower the nitrate levels in the pond water.
The metabolites that probiotic bacteria produce can improve the digestion of the food of the aquatic animals. This can lead to better assimilation of the dietary nutrients and an improvement in growth performance. The microorganisms can also release digestive enzymes and provide the aquatic animal with vitamins, fatty acids and amino acids.
4. Increasing Water Efficiency
A recent study found that commercial probiotics used as water additives significantly reduced NH3 degradation in earthen ponds with Whiteleg shrimp (Litopenaeus vannamei). They also increased water quality, and promoted growth.
The probiotics absorbed organic waste from the water and reduced the amount of nutrients available for pathogens. In addition, they triggered the release of antibacterial peptides and enzymes to prevent pathogen proliferation. This helps reduce the number of antibiotics needed in aquaculture, which is a significant reduction in the use of chemicals that can damage water and soil.
Intensive pond production creates huge quantities of organic waste material that can contaminate the surrounding environment. The bacterium bacillus in our range of aqua probiotics can break down this waste and convert it into nitrates and nitrogen gas – effectively removing the pollution from the water system. This process is incredibly efficient and eliminates the need for manual organic sediment removal between production cycles.
The bacillus probiotics also act as a natural pest control and can suppress pathogens by competing with them for nutrients. They also boost the immune response of the cultured aquatic species – stimulating antibodies, macrophage activation, and interferon production. This results in improved health and resistance to stress, which can be caused by numerous factors during the aquaculture process. This is a major step towards sustainable and environmentally friendly aquaculture.