Assessing changes in macrophyte assemblages with salinity in non-riverine wetlands: A Bayesian approach

Bayesian modeling techniques (which accounted for imperfect detection) were used to assess changes in macrophyte assemblages in 58 wetlands along a typical salinity gradient in Western Victoria, Australia. By incorporating detectability into our predictions, an unbiased estimate was made of the relationship between salinity and both individual species occupancy and the expected number of species. When compared to the freshest wetlands, macrophyte species number was predicted to decrease by as much as 60–70% at conductivities of around 6.0 mS cm−1 (11% seawater), a value often considered the upper salinity tolerance for many freshwater aquatic plants. The model also predicted a 40–50% drop in species number at conductivities of around 1.5 mS cm−1 (3% seawater). It was also found that 25 out of 76 freshwater species were unlikely to occur at conductivities above 1.0 mS cm−1. Consequently, secondary salinisation of fresh non-riverine wetlands is highly likely to markedly and negatively impact upon non-riverine wetland macrophyte assemblages.