To isolate salinity as an environme

To isolate salinity as an environmental variable, controlled laboratory exposure experiments were designed that tested the ability of Austrovenus stutchburyi and Paphies australis from Bradshaw Sound to survive exposure to low salinities. In addition, A. stutchburyi from an east coast site, Otago Harbour (which does not feature a LSL), were included in experiments to compare the salinity tolerance of the species between regions with markedly different salinity environments. Clams were housed at the Portobello Marine Laboratory, in flowing seawater for 2 weeks after collection to allow acclimatization. Individuals from each location were then subjected for 60 days to one of five salinities (0, 5, 10, 17, 34), made with reverse osmosis water and sand-filtered seawater from Otago Harbour. Salinity values are expressed according to the Practical Salinity Scale, which is a conductivity ratio and is unitless. In a separate
experiment, to investigate the influence of the frequency and duration of periods of freshwater exposure on bivalve health and survivorship, clams were subjected to one of four temporal salinity regimes. Treatment salinities were shifted between 0 (freshwater) and 34 (full strength seawater) every 5, 10, 20 or 30 days for a total period of 60 days, resulting in an average salinity of 17 in all treatments. The controls were maintained at a constant salinity of 17.