Effect Of Oil Contamination On Nematode Community Structure And Spatial Distribution In Yellow River Delta Wetlands

The petroleum is the "blood" of modern industry and the biggest energy source in the world. However, with the increase of global oil resource development, the oil production related activities have led to many environmental problems in atmospheric, water environment (including surface water and ground water) and soil environments. The Shengli oilfields are located in the Yellow River Delta wetland with a long-time exploring history and an average of 270,000,000 tons crude oil output per year. Thus, the soil in the oil fields has a great potential to be contaminated by oil pollution. Nematodes are the most abundant soil metazoans playing important roles in soil food webs. With their permeable cuticle, they are in direct contact with the dissolved fraction of contaminants that are accumulated in soil. Nematode community can be used as bioindicators for oil pollution induced disturbances. This study aims to reveal the responses of soil nematode communities to oil exploitation activities at temporal and spatial scales in the Yellow River Delta wetlands.During the study, a total of 39 nematode genera belonging to 6 orders were found from the Yellow River Delta wetlands.The responses of soil nematode communities to the oil exploitation activities in the Yellow River Delta were investigated. By setting 10 oilfield sites and 5 relatively uncontaminated sites (controls), I found that the content of soil TPH was significantly higher at oilfield sites than at controls. With longer oil exploitation history, the content of soil TPH increased. It suggested that the extensive crude oil exploitation has brought contamination to the soil. Soil nematodes were significantly less abundant but more diverse at oilfield sites than at controls. The proportions of fungal feeders were significantly lower at oilfield sites than at controls, attaining only half of those at controls. The nematode trophic diversity and genus number negatively correlated with the duration of petroleum exploitation history. This study elucidated the difference in soil nematode communities caused by oilfield exploitation and indicated that the nematode diversity was most obviously influenced by the soil TPH content and the oil exploitation history.To access the influence of oil pollution on soil nematode spatial distribution, the soil nematode composition were compared between Gudong oilfield and Yellow River Delta national nature reserve by sampling 49 grids at each site. The nematode community showed a clustered distribution in oilfield site and a relatively random distribution in control site. The distribution of fungal feeders, plant feeders and omnivores-predators were clustered in oilfield site, while the distribution of bacterial feeders was random. Fungal feeders in control site showed a random distribution, and plant feeders showed a clustered distribution. The distribution pattern of bacterial feeders and omnivores-predators revealed a relatively clustered distribution in control site. The C /(C₀+ C) ratio of total nematodes was higher in oilfield site than in control, which indicated that the spatial variability of total nematodes in oilfield was fundamentally affected by structural factors, and that in control site was influenced more by random factors. It was expected that the differences in spatial distribution characteristics of soil nematodes would bring about "top-down" and "bottom-up" effects, and finally affect soil food web structure and functioning.