Responses of freshwater biota to rising salinity levels and implications for saline water management: a review

All of the plants and animals that make up freshwater aquatic communities are affected by salinity. Many taxa possess morphological, physiological and life- history characteristics that provide some capacity for tolerance, acclimatisation or avoidance. These characteristics impart a level of resilience to freshwater communities. To maintain biodiversity in aquatic systems it is important to manage the rate, timing, pattern, frequency and duration of increases in salinity in terms of lethal and sublethal effects, sensitive life stages, the capacity of freshwater biota to acclimatise to salinity and long- term impacts on community structure. We have limited understanding of the impacts of saline water management on species interactions, food- web structures and how elevated salinity levels affect the integrity of communities. Little is known about the effect of salinity on complex ecosystem processes involving microbes and microalgae, or the salinity thresholds that prevent semi- aquatic and terrestrial species from using aquatic resources. Compounding effects of salinity and other stressors are also poorly understood. Our current understanding needs to be reinterpreted in a form that is accessible and useful for water managers. Because of their complexity, many of the remaining knowledge gaps can only be addressed through a multidisciplinary approach carried out in an adaptive management framework, utilising decision- making and ecological risk assessment tools.