Assessment of Geosmin Level and Nutrient measurements (ammonia, nitrite, nitrate) in Recirculated Aquaculture Systems (RAS). A case study from African Catfish (Clarias gariepinus) production in Sweden

Abstract

Recirculating aquaculture systems (RAS) offer a promising method of producing fish, but problems such as the presence of geosmin, a compound known for its earthy taste and odour, can affect the quality of the fish This study investigates African catfish (Clarias gariepinus) farmed at the RAS facility in Floda, Sweden, where geosmin-related taste issues have been sporadically observed. Despite the effectiveness of RAS, questions remain regarding it environmental and economic sustainability. The presence of geosmine-producing bacteria in various parts of the RAS system was analysed using analysis of the geosmine coding gene through PCR. The levels of key water quality nutrient parameters - ammonia, nitrite, and nitrate - in the RAS environment were analysed using spectrophotometric methods. The results demonstrated the stability of the water recirculation system and the efficiency of biofiltration. Ammonium, nitrite, and nitrate levels remained below the threshold values and were stable during sample. The used “Cyc” primer was unable to detect the GeoA gene of geosmin-producing bacteria. Further studies using alternative primers and optimization of PCR thermocycling conditions are necessary.