Different fertilization regimes in biofloc systems influence the predominance of distinct bacterial populations, impacting water quality and organism performance. This study evaluates the growth and nutrient absorption of the macroalgae Ulva lactuca when cultivated in an integrated system with Penaeus vannamei and Oreochromis niloticus in chemoautotrophic and heterotrophic systems. The experiment lasted 45 days and comprised two treatments, each with three replicates: chemoautotrophic—utilizing chemical fertilizers; heterotrophic—employing inoculum from mature biofloc shrimp cultivation, supplemented with organic fertilizers. Each treatment consisted of three systems, each containing a 4 m³ tank for shrimp, 0.7 m³ for tilapia, and 0.35 m³ for macroalgae, with continuous water circulation between tanks and constant aeration. Water quality analyses were carried out during the experiment, as were the performances of the macroalgae and animals. The data were subjected to a statistical analysis. Results revealed an increase in macroalgae biomass and the removal of nitrate (57%) and phosphate (47%) during cultivation, with a higher specific growth rate observed in the chemoautotrophic treatment. Nonetheless, the heterotrophic treatment exhibited higher levels of protein in the macroalgae (18% dry matter) and phosphate removal rates (56%), along with superior maintenance of water quality parameters. Tilapia performance varied across treatments, with a higher final weight and weight gain recorded in the heterotrophic treatment. The recycling of water from an ongoing biofloc cultivation with organic fertilization demonstrated viability for macroalgae cultivation within an integrated system involving shrimp and fish.

Blooms of potentially toxic cyanobacteria cause high losses in aquaculture worldwide. The species Nodularia spumigena produces toxin capable of significantly affecting feeding, growth rates, and mortality of shrimp in marine farms. As a result, methods for controlling cyanobacterial blooms can increase the production success. The present study was conducted on a commercial scale using six 600 m ³ ponds stocked with 70 shrimp m ⁻² ( Penaeus vannamei ), in a biofloc system, lasting 15 weeks. The experimental groups were divided into unaffected ponds (WN—without Nodularia ) and affected ponds (N—with Nodularia ), with three replicates ponds per experimental group. Cyanobacterial blooms developed spontaneously in the ponds, and treatments were subsequently designated according to bloom occurrence. During the third week, when the blooms intensified, organic fertilizers consisting of sugarcane molasses and ground commercial feed were added as carbon and nitrogen sources, with the aim of stimulating the establishment of beneficial microbial communities while limiting cyanobacterial proliferation. The water quality parameters were similar between unaffected and affected ponds ( p > 0.05). The microbial community composition was significantly different over time in both grops ( p < 0.05), with the final predominance of chlorophytes. After fertilization, N. spumigena was absent in the affected group (N). The presence of NOD toxin in N. spumigena (66.37 ± 20.87 µg L ⁻¹ ) in the second week affected the feed intake of the shrimp and caused mortalities in affected group. However, N. spumigena and the toxin (NOD) was not detected again in the NS group after organic fertilization and the shrimps recovered. The performance results showed significant differences ( p < 0.05) with higher survival and yield in the unaffected group (WN). Therefore, organic fertilization influenced the occurrence and development of Nodularia spumigena blooms, emphasizing its potential role in the dynamics of cyanobacteria in biofloc shrimp farming and supporting further research.