Acute Toxicity and Bioaccumulation of Aqueous and Sediment-Bound Metals in the Estuarine Amphipod Melita plumulosa C. K. King, 1 S. A. Gale, 2 J. L. Stauber 1 1 Centre for Environmental Contaminants Research, CSIRO Land and Water, Private Mailbag 7, Bangor, New South Wales 2234, Australia 2 University of Technology, Sydney, Westbourne Street, Gore Hill, New South Wales 2065, Australia Received 24 January 2006; revised 8 May 2006; accepted 16 May 2006 ABSTRACT: The sensitivities of juvenile and adult amphipods to metals (Cd, Cu, Ni, Pb, and Zn) in whole sediment and water-only exposures were compared using a newly developed acute test with the estuarine species Melita plumulosa. Endpoints included survival and bioaccumulation in adults, and survival and growth (body length) in juveniles over 96 h water-only and 10 day sediment exposures. Juveniles were more sensitive than adults to metals, either bound to sediments or in the aqueous phase. Although LOEC values for copper and zinc in juvenile whole-sediment tests (820 and 2290 mg/kg dry weight, respectively) were high in comparison with interim sediment quality guideline values for individual metals (270 and 410 for copper and zinc respectively), they were generally within the range of concentrations found in contami- nated sediments in local estuaries. Accumulation of metals, together with the low porewater metal con- centrations in whole-sediment tests, indicated that the ingestion of sediment is an important source of zinc and copper and cause of toxicity in this species. # 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 489–504, 2006. Keywords: amphipods; Melita plumulosa; toxicity; bioaccumulation; whole-sediment bioassays; metals INTRODUCTION Whole-sediment toxicity tests are widely used to assess the toxicity of contaminated sediments (Adams et al., 2005). In Australia, their use is currently limited by a lack of avail- ability of routine tests and lack of information on the com- parative sensitivities of local benthic biota (King et al., 2004, 2006; Simpson et al., 2005). Consequently, interim sediment quality guidelines for Australasia (ANZECC/ ARMCANZ 2000) are largely based on chemical effects data from North America. Benthic amphipods are the most commonly used test organisms in whole-sediment tests as they live in direct contact with the sediment and meet many of the selection criteria for test organisms, such as ecological relevance, sensitivity, and seasonal availability (ASTM, 2003). Amphipods are geographically widely-distributed and are an abundant and ecologically-important component of soft bottom benthic communities. Many species live in burrows within the sediment and/or ingest sediment particles as a source of nutrition. They are generally tolerant to a range of physicochemical characteristics and to handling, and many species can be successfully cultured through generations in the laboratory (Lee, 1977). Amphipods are known to be among the most sensitive benthic organisms to sediment- bound contaminants including PAHs and metals (Ingersoll et al., 1997). In addition, responses of amphipods in toxicity tests have been shown to positively correlate with changes Correspondence to: J. L. Stauber; e-mail: jenny.stauber@csiro.au Contract grant sponsor: NSW Environmental Trust. Contract grant number: 2000/RD/G0003. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/tox.20211  C 2006 Wiley Periodicals, Inc. 489