An environmental study of the macroinvertebrate fauna of three Hobart streams

Three adjacent streams, Cartwright Creek, Lambert Creek, and Sandy Bay Rivulet in the Hobart municipality have their upper catchments relatively unimpacted, but the lower reaches have been affected to various degrees by urban development. An investigation of their macroinvertebrate communities was undertaken to assess their potential usefulness in recognising the impact of development on these three streams. This investigation may provide baseline data and define indicator species which may be useful in the development of biological criteria for water quality assessment. Macroinvertebrate data collection was undertaken from March to November 1998. In total 59 species and 19 107 macroinvertebrate individuals from 9 sites were collected (three sites at each stream). Multivariate analysis including clustering (Two-way Indicator Species Analysis TWINSPAN) and ordination (semi-strong Hybrid Multidimentional Scaling HMDS) was used to recognise assemblages of species typical of each stream, site and season. Significant differences in species composition and diversity were found between the Sandy Bay Rivulet sites where site 1 was different from sites 2 and 3, and between the Cartwright Creek sites. No variation between the Lambert Creek sites was found. Results indicate a strong correlation between impacted sites lower in the catchment and the diversity of species as well as number of individuals. Pollution sensitive invertebrates (especially Ephemeroptera and Plecoptera) were found only at unimpacted sites in the higher reaches of the catchment, and were absent in all lower sites. No Ephemeroptera or Plecoptera were found in Lambert Creek. Two pollution tolerant species, the introduced snail Potamopyrgus antipodarum and the native crustacean Austrogammarus sp, were abundant in all lower sites. Results from this investigation therefore indicate that development has had some detrimental impact on macroinvertebrates at the three streams investigated.