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Ecotoxicity of crude oil polycyclic aromatic hydrocarbons in the páramo ecosystem

2011Ecotoxicity of crude oil polycyclic aromatic hydrocarbons in the páramo ecosystem.CELINSCAK Maja (Croatia)maja.celinscak@gmail.com
Organisation:University of Coimbra, Coimbra (PT) - University San Francisco de Quito, Quito (EC)Supervisor :José Paulo Sousa (UC) & Andrea Encalada (USFQ)
Summary: The effects of heavy crude oil contamination to páramo soil were investigated using a battery of soil and aquatic tests. Earthworm Eisenia fetida and collembolan Folsomia candida were used to test dilutions of soil spiked with 67.2 ml oil/kg (avoidance, lethal tests) and 16.8 mg/kg (reproduction tests). Same soil with 67.2 ml oil/kg was used to prepare eluates for acute and chronic testing with microalgae Pseudokirchneriella subcapitata, fairy shrimp Thamnocephalus platyurus, cladoceran Daphnia magna, rotifer Brachionus calyciflorus and ostracod Heterocypris incongruens. Results indicate that earthworms were in general more sensitive than collembolans with median avoidance (AC50) and lethal concentration (LC50) of 3% and 25.7% of contaminated soil, respectively, for earthworms and AC50 of 17.3% for collembolans. Median effective concentrations (EC50) for juvenile production were 0.5% for earthworms and 3.9% collembolans. Earthworms were more exposed to contaminated soil, since substances can be absorbed through direct contact with the body surface by passive diffusion and through the gastrointestinal tract by soil ingestion. On the other hand, the change of microstructure due to contamination of soil would have enabled the springtails to move through the interstices of the soil (thus decreasing the exposure), while earthworms, for their size, were in constant contact with the contaminant. In aquatic tests cladocerans and rotifers were similarly affected by oil with LC50 values of 55.9% and 56.5% of eluate, respectively. Ostracods were the most sensitive species and showed total mortality with all eluate dilutions tested, but fairy shrimp and microalgae did not show negative effects of the contamination. Most of the results are in agreement with other research and sublethal assays proved to be the most sensitive. Considering these results, an oil spill in the páramo system could have devastating consequences on both soil fauna and nearby aquatic organisms through leaching. Most of the results are in agreement with other research and sublethal assays proved to be the most sensitive, so they should not be avoided despite their costs and length. The proposed battery of tests based on this study consists of earthworm and collembolan avoidance and chronic tests in soil assays and cladoceran acute, rotifer acute and chronic and ostracod chronic tests in aquatic assays.
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