The Toxicity of Laboratory Burned Oil to the Amphipod Allorchestes compressa and the Snail Polinices conicus ISMAIL GULEC & DOUGLAS A. HOLDWAY* Oil Spill Research Group, Department of Applied Biology and Biotechnology, RMIT City-Campus, P.O. Box 2476V, Melbourne,Vic. 3001, Australia Acute 96 h LC50 values of the burned-oil±water-accommodated-fraction (BWAF) and burned-oil-residue- mixture (BRM) were determined in semi-static bioassays with seawater, using the amphipod Allorchestes compressa (Dana). Sublethal bioassays (suppression of burying behaviour over 30 min and 24 h exposure) were also conducted for these toxicants, using the marine sand snail Polinices conicus (Lamarck) as the test organism. The mean (n  4) 96 h LC50 (S.E.) value for BWAF was 80 (4.1)% and for BRM was greater than 100%. No-observed-eect-concentration (NOEC) and lowest-observed-eect-concentration (LOEC) for the both toxicants were 40% and 60% respectively. The burying behaviour of the snails after 30 min exposure to both toxicants was not aected with NOEC values greater than 100%. The 24 h EC50 (S.E.) value for BWAF was 60 (2.7)% with 10% NOEC and 20% LOEC values. The respective 24 h EC50 value for BRM was greater than 100% with 40% NOEC and 60% LOEC values. Ó 1999 Elsevier Science Ltd. All rights reserved Keywords: In situ burn, bioassays, toxicity, LC50, EC50 Introduction In situ burning is attracting scienti®c interest as a treatment of oil spills in the marine environment. It may be especially useful in cold climate regions where spilled oil gets thickened and becomes impossible for mechanical clean-up and dispersion, or in the presence of ice (Fingas, 1995). Dispersants are commonly used in warm climate regions because mechanical clean-up can only recover a limited amount of oil (T. Budd, Pers. Comm.). However, the use of dispersant does not remove the oil from water but rather chemically causes the oil to sink. In contrast, in situ burning re- moves the spilled oil at very high rates and does not require any disposal (Fingas, 1995) (with only a small amount of non-toxic semi-solid residue to collect). In addition, reduced supporting infrastructure and equipment is necessary for this remedial action (Fingas, 1995). Spilled oil must often be contained at a sucient thickness (1±2 mm) to permit burning and ignition, because of the cooling eect of the seawater under- neath the slick (Allen, 1997). Fire resistant booms are used for this purpose since the temperature in ¯ames can reach up to 1000±1200°C (Lazes, 1994). The major concern of in situ burning is the atmospheric emis- sions, which include the smoke plume, particulate matter precipitating from the smoke plume, combus- tion gases and unburned hydrocarbons (Fingas et al., 1994). The release of particulates from the smoke plume are the main hazard of atmospheric emissions. The other emissions are similar or only slightly dif- ferent from background levels 300 m removed from the burning site (Fingas et al., 1994). The release of particulates from burning can aect the human re- spiratory system. These particles are generally less Spill Science & Technology Bulletin, Vol. 5, No. 2, pp 135±139, 1999 Ó 1999 Elsevier Science Ltd. All rights reserved. Printed in Great Britain 1353-2561/99 $ ± see front matter PII: S1353-2561(98)00025-5 135 *Corresponding author. Tel.: +61-3-9925-2110; Fax: +61-3-9662- 3421; E-mail: d.holdway@rmit.edu.au