Seeding as a start-up strategy for improving the acclimation of freshwater nitrifying bioreactors to salinity stress

Recirculating aquaculture systems (RAS) for anadromous fish such as salmonids often require salinity changes during the production cycle. However, high or variable can disrupt biological nitrification process, which be detrimental to due accumulation of toxic ammonia nitrite. Thus, it is vital maintain sufficient capacity in RAS changes. This study investigated whether seeding with salinity-acclimated carriers freshwater start-up phase could increase tolerance nitrifying bioreactors. Moving bed biofilm reactors (MBBR) were started virgin and seeded mature acclimated (F), brackish water (B, 12‰ salinity), a 1:1 mix both (FB). All duplicate up was increased seawater (~32‰ salinity) after ~7 weeks. While F FB had 65–75% decrease oxidation immediately transfer, B only ~20% reduction. After 40 days seawater, recovered completely became similar all treatments. nitrite observed treatments several increase, least highest F. The type influenced composition microbial community new biofilms (in phase). ~6 weeks seawater. findings indicate that potential strategy accelerating improving acclimation bioreactors stress. oxidizing bacteria may longer period adaptation. important closely monitor concentration prolonged (several weeks) increase.