Propagules in dry wetland sediments as indicators of ecological health: effects of salinity

Indicators of ecological health are problematic for wetlands in dry regions because distinctive communities are associated with dry and wet phases of indefinite duration. The propagule bank, including the resting stages of aquatic animals and plants, maintains the community's capacity to recover from drought or disturbance. This paper records observations of invertebrates, protists and algae emerging in laboratory microcosms following the inundation of dry sediments from two temporary lakes on the River Murray floodplain in South Australia. A simple experiment carried out on the sediment from one lake showed that increased salinity was associated with lower diversity (richness) but higher abundance of emergent organisms. The effect on diversity was evident at salinities above 11–17 mS cm−1, and the effect on abundances was evident above 6–11 mS cm−1 (salinity here is indicated by electrical conductivity at 25°C). These data suggest that propagule banks may be useful as complementary indicators of wetland health.