Differences in invertebrate infaunal assemblages of constructed and natural tidal flats in New South Wales, Australia

Abstract

The infauna at four natural and two constructed tidal flats were sampled to determine differences in assemblages on the southeastern coast of New South Wales, Australia. Spatial variation within location (tidal heights and subsites separated by 50–100 m) and between locations was incorporated into the design to investigate differences in species assemblages between constructed and natural locations. Overall, infauna at constructed locations were intermediate in abundance and species richness, although differences in abundance and species richness across tidal heights were observed at some locations. Multivariate analysis of species composition revealed distinct differences in species assemblages between constructed and natural locations, amongst tidal heights, and considerable spatial variation within any location. Inappropriate design of waterflow at the oldest constructed site is believed to be responsible for the low variability in species assemblages within this location which are characterised by early successional species that occur in disturbed tidal flats. The newer constructed tidal flat appeared to have adequate waterflow, high site variability in species composition and an infaunal assemblage typical of an early successional stage. The importance of measuring spatial variability in monitoring is stressed in order to make useful comparisons between constructed and natural tidal flats. This study showed that the successful construction of a mature and healthy tidal flat requires the maintenance of a significant waterflow area to ensure adequate tidal flow for the establishment of fauna.