Toxicological Effect Of Pyrene Exposure On Pinctada Martensi

Ocean pollution with persistent organic pollutants (POPs) poses an environmental problem of international concern. Polycyclic aromatic hydrocarbons (PAHs), a group of highly carcinogenic, teratogenic and mutagenic persistent organic pollutants, have been listed as priority pollutants by the U.S. Environmental Protection Agency due to their toxicity towards the environment and living organisms. Pyrene (Py), a typical PAH consisting of four4fused aromatic rings, is commonly found in aquatic ecosystems. Due to their sessile lifestyle and high capacity to accumulate organic pollutants, marine bivalves are commonly used as biomarkers for monitoring marine environment pollution. So far, there have been no published studies on ecotoxicological effects of pyrene exposure on important commercial species of tropical ocean pearl oyster Pinctada martensi. This research project used cytological, ecotoxicological and biochemical methods to examine the effects of Py exposure on early embryonic development of Pinctada martensi at the organismal, tissue and cellular levels. Py effects on non-specific immune function and oxidative stress in the haemolymph of adult organisms as well as the DNA damage in embryo cells were also examined. Analysis of pyrene dose-response relationships and screening of sensitive biomarkers reveal the mechanisms of pyrene toxicity to marine organisms and provide early warning for chemical pollution in marine environment. Such data can provide scientific basis for conducting ecological risk assessment. Following research conclusions were reached:1. Pyrene has notable toxic effect on development of D-shaped veliger larvae. Exposure to higher concentrations of pollutant caused significant increase in abnormally shaped veliger larvae, with clear dose-response relationship. Larvae were most sensitive to pyrene concentrations of8μg·L-1and32μg·L-1. Mortality of D-shaped veliger larvae positively correlated with both Py concentrations and length of exposure. With longer exposure times, LC50decreased, reaching43.50μg·L-1at60hours of exposure. It can be concluded that Py exposure causes adverse effects on the development of D-shaped veliger larvae of Pinctada martensi and the population structure of Pinctada martensi.2. Pyrene pollution has an obvious impact on non-specific immune defense system and antioxidant enzyme activity in Pinctada martensi. With exposure to4～64μg·L-1pyrene, the total number of haemocytes decreased, following a dose-response relationship. Meanwhile cell membrane stability was reduced and phagocytosis activity decreased. Py also caused a significant decrease in total glutathione (GSH) and a significant increase in lipid peroxidation (MDA), indicating the development of oxidative stress 3. Pyrene induces obvious DNA damage in embryo cells in Pinctada martensi. Higher pyrene concentrations increased the average length of DNA migration, exhibiting a significant dose-effect relationship. Longer duration of pyrene exposure also increased the average length of DNA migration at4h to8h exposure time, then decreased at16h, exhibiting a significant time-effect relationship. These data indicate that pyrene may damage Pinctada martensi DNA.4. Developmental and morphological changes of D-shaped veliger larvae, changes in non-specific immune function and oxidative stress, and the DNA damage in embryo cells of Pinctada martensi can be used as sensitive biomarkers for pyrene pollution of marine environment.