2545 Environmental Toxicology and Chemistry, Vol. 24, No. 10, pp. 2545–2552, 2005  2005 SETAC Printed in the USA 0730-7268/05 $12.00 + .00 SENSITIVITY OF AN INDIGENOUS AMPHIPOD (COROPHIUM COLO) TO CHEMICAL CONTAMINANTS IN LABORATORY TOXICITY TESTS CONDUCTED WITH SEDIMENTS FROM SYDNEY HARBOR, AUSTRALIA, AND VICINITY STEPHANIE MCCREADY,*² C HRISTOPHER R. GREELY,² R OSS V. HYNE,‡ GAVIN F. BIRCH,² and EDWARD R. LONG§ ²Environmental Geology Group, School of Geosciences, University of Sydney, New South Wales 2006, Australia ‡New South Wales Department of Environment and Conservation, Centre for Ecotoxicology, P.O. Box 29, Lidcombe, New South Wales 1825, Australia §ERL Environmental, 3691 Cole Road South, Salem, Oregon 97306, USA ( Received 8 September 2004; Accepted 6 April 2005) Abstract—Laboratory survival tests were conducted with an indigenous infaunal amphipod, Corophium colo, on 103 sediment samples from Sydney Harbor (NSW, Australia) and vicinity, containing a wide range of chemicals and concentrations. The present study describes the sensitivity of C. colo to the sediments and compares the results to data for North American amphipods (Rhepoxynius abronius and Ampelisca abdita) previously used to establish and validate sediment-quality guidelines (SQGs). The incidence of toxicity increased with increasing contamination, as indicated by increasing numbers of SQGs exceeded and increasing mean SQG quotients. The incidence of highly toxic results (p  0.05 and mean amphipod survival of 80% that of controls) for highly contaminated samples was approximately half (28–40%) that of a large U.S. database (74%). The incidence of highly toxic responses for samples with intermediate levels of contamination also was lower in the present study (5–13%) compared to the results in large U.S. studies (30–50%). Corophium colo reburial tests showed greater sensitivity compared to survival tests, with a maximum incidence of statistically significant responses in moderately contaminated sediments of 70%. The present study showed that adult Corophium organisms are suitable for testing lethal responses in highly contaminated sediments (i.e., with mean effects range-median quotients of 1.5). Reburial results provide additional sensitivity. Keywords—Corophium Sediment toxicity Sydney Harbor Amphipod INTRODUCTION Amphipods are widely used test organisms in sediment tox- icity assessments [1–4] and are commonly used in 10-d lab- oratory survival tests of whole sediments following established guidelines [5]. Amphipod survival tests are considered to be ecologically relevant, because amphipods are common mem- bers of the benthic community, are sensitive species not gen- erally found in polluted areas [6], and are an important source of food for birds and fish [7]. In addition, the tests involve minimal manipulation of sediments compared to other ex situ tests, and both particulate and pore-water routes of exposure to contaminants may be accounted for. Because of these at- tributes, the amphipod survival test is frequently used for both regulatory applications and ambient monitoring in the United States and Canada [8]. Use of the amphipod genus Corophium in sediment toxicity tests is well established, particularly in Europe [9–14], and standard test protocols are available for Corophium spp. [15,16]. This genus is widely distributed along the western European and northeastern American coasts, where it fre- quently is found in muddy intertidal areas [7]. It builds U- shaped burrows, and densities may exceed 100,000 organisms/ m 2 [7]. Corophium organisms feed in two ways: First, by deposit feeding, in which particles are gathered from the sediment surface with the enlarged second antennae; and second, by * To whom correspondence may be addressed (bendeich@ozemail.com.au). suspension feeding, in which particles are filtered through a basket formed by the setae of the second gnathopods under the influence of the respiratory current [17]. The relative im- portance of each mode of feeding is unresolved and may vary for different species of Corophium. [18]. Corophium can only ingest particles of 4 to 63 m in size [17], and their guts usually are filled with clay/silt particles [19]. Corophium spp. also may browse on particles that are smaller or larger than the size that can be swallowed, scraping off attached organic material with teeth-like structures on the first pair of gnath- opods [20]. Corophium organisms therefore are exposed to particulate-bound contaminants during feeding. A recently described species, Corophium colo [21], is prev- alent at muddy locations in the Hawkesbury River estuary, New South Wales, Australia, which is the major river catch- ment in the Sydney region [22,23]. Corophium colo is found year-round at brackish intertidal locations within this estuary, making it a viable organism for toxicity tests [22]. The species breeds continuously from spring to autumn (with an overwin- tering population from June to August), and peak densities are 9,000 organisms/m 2 [22]. A 10-d survival test has been de- veloped for this organism [23] and is the only published whole- sediment toxicity test for Australia. In the present study, sur- vival tests with C. colo were conducted on 103 surficial salt- water sediment samples containing a wide range of contami- nants and concentrations. The samples were from Sydney Harbor, New South Wales, Australia, as well as from coastal lakes and estuaries south of Sydney. Corophium spp. have not been tested previously on a large range of field-collected sed- iments in Australia.