Dose and accumulative effects of spent lubricating oil on four common mangrove plants in South China

The growth of four mangrove species seedlings, namely Bruguiera gymnorrhiza, Kandelia obovata, Aegiceras corniculatum and Acanthus ilicifolius in sediments contaminated by spent lubricating oil, even at the lowest oil dose (2.5Lm^-2), showed different degrees of sub-lethal damages. All the seedlings of K. obovata and A. corniculatum were killed at 10Lm^-2 oil, while the lethal oil dose was 15Lm^-2 for A. ilicifolius seedlings. B. gymnorrhiza was the most tolerant species to oil pollution, which could survive under the highest oil dose treatment (15Lm^-2). Biochemical responses including superoxide radical (O₂^-) release, superoxide dismutase (SOD) activity and malonyldialdehyde (MDA) content in both leaves and roots of the oil-treated seedlings were increased significantly with oil dose, and presented a positive relationship with leaf and root biomass.