Effects of environmental stresses on the responses of mangrove plants to spent lubricating oil

摘要

The influence of different environmental stresses, including salinity (5-35‰), tidal cycle (6/6,12/12 and 24/24 h of high/low tidal regimes) and nutrient addition (1-6 times background nitrogen and phosphorus content) on Bruguiera gymnorrhiza and Aegiceras cornkulatum grown in sediment contaminated with spent lubricating oil (7.5 L m"2) were investigated. The oil-treated 1-year-old mangrove seedlings subject to low (5‰) and high (35‰) salinity had significantly more reduction in growth, more release of super-oxide radical (O2'~) and higher activity of superoxide dismutase (SOD) than those subject to moderate salinity (15‰). Extended flooding (24/24 h of high/low tidal regime) enhanced O_2'~ release and malondi-aldehyde (MDA) content in both oil-treated species but had little negative effects on biomass production (P>0.05) except the stem of A corniculatum (P = 0.012). The addition of nutrients had no beneficial or even posed harmful effects on the growth and cellular responses of the oil-treated seedlings.