Aquaculture is one of many businesses that produces effluents with high or changing salt concentrations. Due to the sensitivity of the bacteria involved in the biological nitrification process to salinity, treating such effluents might be difficult. It is crucial to maintain high nitrification efficiency during salinity fluctuations in some circumstances, such as in Recirculating Aquaculture Systems (RAS), to avoid ammonia and nitrite toxicity. As a result, appropriate techniques are needed to make nitrifying bioreactors resistant to changes in salinity. It has been demonstrated that nitrifying bioreactors can adapt to salinity variations over a number of days, despite the fact that salinity changes can have an impact on nitrification performance. The physiological adaptation of the existing microorganisms or the selection of microorganisms adapted to that salinity regime may be the cause of this acclimation. Salinity acclimation may be influenced by a variety of other variables, including the biofilm matrix. Recent research has demonstrated that microbial management techniques can be used to increase the salinity tolerance and shorten the recovery period of nitrifying bioreactors. Here, we go over the current understanding of salinity acclimation in nitrifying systems as well as recent developments in methods for increasing the salinity tolerance of nitrifying biofilms. We also suggest areas for future study to enhance our comprehension of the mechanisms nitrifying systems use to adapt to salinity.
