PRIMARY RESEARCH PAPER Spatial variation of intertidal macroinvertebrates and environmental variables in Robbins Passage wetlands, NW Tasmania Fiona L. Spruzen Æ Alastair M. M. Richardson Æ Eric J. Woehler Received: 7 March 2007 / Revised: 30 August 2007 / Accepted: 11 September 2007 / Published online: 5 October 2007 Ó Springer Science+Business Media B.V. 2007 Abstract Macroinvertebrate composition, abun- dance and biomass were investigated at four intertidal sites throughout the Robbins Passage wet- lands, Tasmania, over a 12-month period, in order to identify differences among and within sites, and to determine whether environmental variables could explain these differences. As this region is the most important shorebird area in Tasmania, we wanted to quantify the potential food source for shorebirds within the wetlands. Thirty-five taxa from 28,928 individuals were identified, with a mean abundance of 6026.6 ind m –2 and biomass of 27.1 gDW m –2 . Bivalves and gastropods dominated the assemblage in terms of abundance and biomass (79% and 60%, respectively). There was a significant interaction among tidal level, site and season for invertebrate abundance and diversity, while biomass differed significantly among sites. In general, the mid-inter- tidal stratum had the greatest invertebrate density and diversity, while the low intertidal stratum had the greatest biomass. Community composition varied among the four sites, with the bivalve Paphies elongata dominating at two of the sites, while gastropods and polychaetes were more abundant at the other sites. Differences in invertebrate composi- tion and abundance could partly be explained by seagrass biomass, i.e., dry mass of seagrass leaves and roots. Areas with seagrass had increased inver- tebrate abundance and diversity, but mean sediment particle size, % organic carbon and % seagrass cover had no significant effect. These results will assist in the investigation of habitat use by shorebirds and the identification of important shorebird feeding areas within the wetlands. Keywords Benthic macroinvertebrates Á Tidal flats Á Distribution Á Biomass Á Seagrass Introduction Intertidal flats, areas of the coast that are alternately covered and uncovered by tidal action, are dynamic ecosystems, providing food and habitat for many organisms. Intertidal benthic invertebrate communi- ties are a vital part of these ecosystems and an important food source for terrestrial predators such as shorebirds as well as marine predators such as fish. These invertebrate communities change on spatial and temporal scales (Ysebaert & Herman, 2002; Rodrigues et al., 2006). Knowledge of their compo- sition and distribution is essential to understand an intertidal ecosystem and its processes, and more specifically, feeding, habitat use and distribution of shorebirds. Handling editor: P. Viaroli F. L. Spruzen (&) Á A. M. M. Richardson Á E. J. Woehler School of Zoology, University of Tasmania, Private Bag 5, Hobart, Tasmania 7001, Australia e-mail: lspruzen@utas.edu.au 123 Hydrobiologia (2008) 598:325–342 DOI 10.1007/s10750-007-9166-2