Fluctuating salinity improves survival of the invasive freshwater golden mussel at high salinity: implications for the introduction of aquatic species through estuarine ports

In order to evaluate the resilience to salinity as a factor enhancing freshwater invasiveness, we assessed the tolerance of the mussel Limnoperna fortunei to salinity conditions mimicking changes in an estuary. We tested mussel mortality in 30-day exposures to constant and fluctuating salinities at different temperatures in the laboratory. Test conditions simulated different seasons of the year and locations with increasing influence of marine waters in Río de la Plata, Argentina. Significant mortality (31% after 30 d) was observed at a constant salinity of 2?, increasing to 45% and 57% at 5? and 10?, respectively. In contrast, considerably greater tolerances were observed when conditions in the experimental chamber fluctuated between salt- and fresh water. No significant mortality was observed in mussels exposed to a salinity cycle with abrupt salinity changes ranging 1-23? (mean 2.68?) over a month. Tolerance to this type of regime was unaffected by different temperatures within ambient ranges. Tests at constant salinity underestimate the tolerance of this and probably other freshwater nonindigenous species (NIS) to short term saltwater exposures. Estuarine ports account for ca ⅔ of non-marine ports globally, thus constituting hotspots for NIS propagule pickup and delivery into continental aquatic ecosystems via shipping vectors. The tolerance of L. fortunei to estuarine conditions likely contributes to the species? remarkable invasive success. These results highlight the need to determine causes of invasiveness, and study NIS traits not alone but in combination with transport network properties.Fil: Sylvester, Francisco. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; Argentina;Fil: Notaro, Carolina. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; Argentina;Fil: Cataldo, Daniel. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; Argentina; Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Museo Arg.de Cs.nat;Fil: Boltovskoy, Demetrio. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Ecologia, Genetica y Evolución; Argentina; Consejo Nacional de Invest.cientif.y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Museo Arg.de Cs.nat