Effects of reduced pH on an estuarine penaeid shrimp (Metapenaeus macleayi)

Acid sulfate soils are a major problem in modified coastal floodplains and are thought to have substantial impacts on estuarine species. In New South Wales, Australia, acid sulfate soils occur in every estuary and are thought to impact important fisheries species, such as Eastern School Prawn (Metapenaeus macleayi). These fisheries have experienced declining productivity over the last ten years and increasing occurrence of catchment-derived stressors in estuaries contribute to this problem. We evaluated the effect of pH 4-7.5 on School Prawn survival at two salinities (27 and 14.5), pH 5, 6 and 7.5 on the predation escape response (PER) speed at two salinities (27 and 14.5), and pH 4 and 7.5 on respiration rates. While mortality appeared to be greater in the high salinity treatment, there was no significant relationship between proportional survival and pH for either salinity treatment. Respiration was significantly slower under acidic conditions and the average PER was almost twice as fast at pH 7.5 compared to pH 5 (p < 0.05), indicating prawns may fall prey to predation more easily in acidic conditions. These findings confirm the hypothesised impacts of acidic water on penaeid prawns. Given that the conditions simulated in these experiments reflect those encountered in estuaries, acidic runoff may be contributing to bottlenecks for estuarine species and impacting fisheries productivity.