International Journal of Aquaculture, 2026, Vol.16, No.1, 46-60 http://www.aquapublisher.com/index.php/ija 52 blue-green algae like Microcystis in a wide range of pH conditions. If used properly, they have a relatively small impact on the water's acidity and alkalinity, produce little dissolved organic carbon, and can decompose microcystin-LR and chlorophyll a. Moreover, these oxidants also have a strong killing effect on marine flagellates that are harmful to fish, making them a potential alternative to chlorine in ship ballast water treatment and coastal water management. However, although chemical treatment can take effect quickly, it also brings some environmental and management issues. For instance, copper preparations and some synthetic herbicides may gradually accumulate in sediments or aquatic organisms, thereby posing long-term ecological risks. At the same time, when herbicides or oxidants cause a sudden death of a large number of algae, toxins and organic substances in the cells will rapidly be released into the water, which may increase toxicity in a short period and lead to oxygen deficiency in the water body. Some recent review studies have also pointed out that in practical applications, most chemical treatment measures are difficult to improve water quality in the long term, indicating that relying solely on chemical agents is insufficient to solve the problem of excessive nutrients at the watershed level (Table 1) (Lan et al., 2024). Some recently emerged nano-material oxidants and photocatalysts can improve treatment efficiency and selectivity, but they also raise new issues, such as the fate of nanoparticles in the environment and whether they will be toxic to the ecosystem. The current situation is unclear. Therefore, in practical management, chemical methods are more often used as emergency or short-term control measures. When using these agents, strict control of dosage, enhanced monitoring, and their integration into a prevention-oriented comprehensive management strategy are necessary. Table 1 Innovative fertilizer technologies for reducing eutrophication (Adopted from Lan et al., 2024) Fertilizer Technology Nutrients Provided Mechanism Suitable Crops Slow-Release Fertilizers (SRFs) Nitrogen, Phosphorus, Potassium Gradual nutrient release aligned with crop uptake Cereals, horticultural crops, turfgrass Controlled-Release Fertilizers (CRFs) Nitrogen, Phosphorus, Potassium Coating controls nutrient release over time Vegetables, fruits, ornamental plants Nitrification Inhibitors Nitrogen Inhibits nitrification, reducing nitrate leaching Maize, wheat, rice Urease Inhibitors Nitrogen (Urea-based) Prevents rapid urea conversion, reducing ammonia loss Rice, cereals, pasture Enhanced Efficiency Fertilizers (EEFs) Nitrogen, Phosphorus Combines slow and controlled release with inhibitors Various crops including cereals, fruits, vegetables Polymer-Coated Fertilizers Nitrogen, Potassium Encapsulated nutrients in a polymer for controlled release High-value crops like fruits, vegetables, ornamentals Biochar-Enhanced Fertilizers Nitrogen, Phosphorus, Potassium, micronutrients Uses biochar to retain nutrients and reduce leaching Cereals, legumes, vegetables Struvite Fertilizers Phosphorus, Nitrogen, Magnesium Mineral compound with slow nutrient release Horticultural crops, cereals 4.3 Biological methods: using microorganisms, filter-feeding organisms and aquatic plants Biological control methods involve using predator relationships, species competition, or microbial actions to inhibit the growth of harmful algae. This approach is generally considered more environmentally friendly and more in line with natural ecological laws. Microbial control mainly includes the use of bacteria, fungi, or actinomycetes that can kill algae, or the use of some microbial groups to cause the cell lysis of algae, inhibit their growth, or cause the aggregation, sedimentation, and gradual decomposition of algae cells, thus forming a process of "aggregation-lysis-degradation-nutrient regulation". Relevant research and reviews indicate that some strains with algicidal effects, such as certain streptomyces, vibrio, and the algicidal fungus known as D7, not only can reduce the number of algae in water bodies, but can also, to a certain extent, lower the nutrient salt levels in water, thereby simultaneously alleviating the problems of algal blooms and excessive nitrogen and phosphorus (Anabtawi et al., 2024; Pan et al., 2025). Most related studies are still at the stage of laboratory or medium-scale simulation tests, and there is not sufficient evidence to prove that they can improve the long-term water quality of
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