Microbial dynamics in a IoT-monitored recirculating aquaculture system (RAS) for culturing mud spiny lobster (Panulirus polyphagus)

In this study, we evaluated the feasibility of a rearing system for mud spiny lobster ( Panulirus polyphagus ) consisting of individual containers within a recirculating aquaculture system (RAS), enhanced with an automatic water quality monitoring system (Aqua IoT), over 45 days. Twenty P. polyphagus juveniles were fed fresh fish and squid twice daily. The initial average body weight of the lobsters was 159.67 + /- 55.50 g, increasing to 253.00 + /- 60.42 g by the end of the experiment. The survival rate was 70.00%, while the average daily growth rate was 2.07 g/day, with a specific growth rate of 1.02%. The accumulated molting rate was recorded as 60.00%, with the first molting event observed on day 14. Water quality parameters remained within optimal ranges (temperature: 26.5–29.9 C, total ammonia: 0.00–0.25 mg/L, nitrite: 0.00–2.00 mg/L, salinity: 28.5–32.6 g/L, pH: 7.69–8.27, water hardness: 119.00–212.50 mg/L, magnesium: 525–1200 mg/L, calcium: 280–400 mg/L, and total dissolved solids: 20,636.00–26,445.00 mg/L). Bacterial community profiling revealed a shift from an initial dominance of Cyanobacteria and organelle-associated sequences to a more diverse community enriched with Bacteroidota, Proteobacteria, and putative denitrifiers such as Ruegeria , Arcobacter , and Fusibacter . LEfSE analysis identified key microbial taxa potentially associated with nitrogen cycling and organic matter degradation. Because these inferences are based on 16S rRNA taxonomic profiling rather than functional-gene, metagenomic, or activity measurements, the nitrogen-cycling roles are interpreted as potential associations. These findings suggest that an IoT-monitored RAS can provide a stable environment for the culture of P. polyphagus while supporting microbial succession and growth performance; however, the IoT component served primarily as a real-time monitoring aid and was not experimentally isolated as a direct driver of production performance.