Relationship between the crustacean and molluscan assemblages of Tasmanian saltmarshes and the vegetation and soil conditions

Abstract

The crustacean and molluscan fauna of 65 saltmarshes around the Tasmanian coast were sampled at three tidal levels and in three broad vegetation types, and the salinity and organic and moisture content of the substratum were measured concurrently. Of the 55 species of crustaceans and molluscs collected, eight (four snails, three amphipods and a crab) were confined to saltmarshes. Ordination of the animal data grouped the sites by the degree of submersion, whereas ordination of the vegetation data grouped them by the salinity of the substratum. The faunal composition could not be predicted by the plant communities on a marsh, nor were there any strong relationships between individual animal and plant species. Most crustaceans and molluscs tolerated a wide range of soil conditions, but terrestrial species such as landhoppers and woodlice were not associated with highly saline substrata. Emergent marshes (as identified by the faunal analysis) tend to be most common in the north-east and on Flinders Island, whereas submergent marshes are found all round the coast. Reedy brackish marshes (as identified by the vegetation analysis) are almost entirely confined to the west coast.