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(62-02) The role of earthworms in the assessment and remediation of oil contaminated soil. Schaefer, Maike*,1, Filser, Juliane1, 1 Centre for Environmental Research and Environmental Technology (UFT), University of Bremen, Bremen, Germany ABSTRACT- Oil pollution is a worldwide prevalent threat to the environment. Great efforts have been made in order to monitor and successfully remediate oil contaminated soils, sediments and waters. Soil organisms are directly exposed to soil contaminations. Earthworms, as typical representatives of the soil fauna, serve not only as test organisms in various ecotoxicological tests, but also affect the degradation of organic compounds, possibly including oil contaminations. In order to study their role in bioremediation processes different earthworm species (Eisenia fetida, Lumbricus terrestris and Allolobophora chlorotica) were incubated in a crude-oil contaminated soil, with an initial test concentration of 10.000 mg/kg (total hydrocarbon concentration). The earthworm species differed not only in their sensitivity towards oil in the applied toxicity tests (acute, reproduction test), but also in their impacts on oil degradation. Whereas E. fetida and A. chlorotica showed mortality rates of 15-20 %, up to 68% of all individuals of L. terrestris died within 14 days. Incubation with L. terrestris and E. fetida resulted in significant reductions of the hydrocarbon concentrations at test end (28 d), i.e. 42 to 64 % less compared to controls without worms. Supposing that the lumbricids enhance oil degradation via enhancing microbial activity (increased oxygen supply due to burrowing activities, increase of microbial biomass during gut passage) and via changing microbial community structures, soil respiration measurements and PLFA (phospholipid fatty acid) analyses were carried out. The simulation of earthworm burrowing activity by mechanical mixing had no effect on oil degradation, but soil respiration was related to it. Similar changes in soil PLFA composition was observed with all earthworm species. Key words: earthworm ecotoxicology, crude-oil contamination, PLFA, soil respiration |
