| This study can be divided into three parts, the first part investigated the responses of marine nematodes to crude oil contamination in polluted and relatively uncontaminated sites,40days after an oil spill. Samples were taken at different tide levels on the beach and at different positions along the beach. We present the results of a comparison of nematode assemblages from undisturbed sediment from the Xiajiahezi Bathing Beach with those from sediment from the Xinghai Bathing Beach contaminated with crude oil. A total of1666nematodes from26genera were found in this study. Results showed significant differences in nematode assemblages between samples from undisturbed controls and those from the polluted area. Nematode abundance, number of species, diversity and species richness decreased significantly with increasing levels of crude oil contamination. Fifteen genera were eliminated and seemed to be composed of species intolerant to crude oil contamination; only the abundance of Marylynnia sp. increased slightly.The second part studied effects of single cadmium (Cd), mix of Cd and chromium (Cr), Cd and mercury (Hg) on a nematode assemblage after three months application. Morning glories (Pharbitis nil) as heavy metal accumulators were grown on the experimental pots, the adsorption capacity showed a decreased trend with increasing concentration of heavy metals. Both single Cd and mixed heavy metals had marked effects on the nematode density, c-p (colonisers-peisisters) structure and feeding type composition. Cd was harmful to Eucephalobus which was eliminated at all the Cd doses tested, while mix Cd and Hg increased its number. Cd increased the proportion of c-p3-5groups, MI values, MI2-5values and SI values, decreased the proportion of c-p1group and bacterivores. Comparing with single Cd, interaction of Cd and Cr decreased fungal/bacterial ratio and MI values, interaction of Cd and Hg increased Rhabditis number and decreased MI values.The last part investigated soil nematode communities under different vegetation types from suburb forest park and square greenland at two soil depths (0-10cm,10-20cm). Soil nematode community structure and composition at three kinds of vegetation types (coniferous forest CF, mixed forest MF and broad-leaved forest BF) were compared. The results showed that a total of8541nematodes belonging to40genera were identified, the total abundance of soil nematodes decreased with increasing soil depth in all vegetation types. Maturity index (MI), Structure index (SI) and channel index (CI) had the same trend: BF>MF>CF; while Shannon index or diversity (H’), Evenness index (J’), Plant-parasitic Maturity index(PPI), PPI/MI and Basal index (BI) were in order of CF>MF>BF. Our results indicated that coniferous forest was most disturbed among all sites. Soil properties showed significant correlation with total number of nematode, individual density, genera and ecological index. When it comes to square greenland, square lawns (SL), roadside bushwood (RB) and roadside trees (RT) were chose as sampling sites. Soil moisture, pH, total phosphorus (TP), were in order of SL> RB> RT, while contents of total cadmium (Cd), total lead (Pb) and total zinc (Zn) had the opposite trend. Lowest values of nematode density, generic richness (S), nematode channel indices (CI) and highest values of fungivore/bacterivore (f/b) and plant-parasitic nematodes maturity index/maturity index (PPI/MI) appeared at roadside trees. Our results indicated that soils under roadside trees were most disturbed. Soil properties showed significant correlation with nematode density, generic richness and ecological index, which means abundance and structure of soil nematode can indicate soil quality in urban greenland. |
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