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(W/MF141) Toxicity assessment of an urban effluent to the mussel Mytilus galloprovincialis using a simple microcosmos system. Moreira, Susana1,2, Guilhermino, Lúcia1,2, 1 2 ABSTRACT- Urban effluents discharged into aquatic ecosystems may be responsible for disturbances in biological communities. As biological indicators of pollution, marine mussels have been extensively used because of their filter-feeding habit, sessile nature and wide geographical distribution. The main objective of this study was the toxicity assessment of an urban effluent, discharged directly into the intertidal zone, to Mytilus galloprovincialis using a simple microcosmos system. Mortality and effects on acetylcholinesterase (AChE) and glutathione S-transferase (GST) were used as indicative criteria. In order to take into account the possible salinity interference and to increase ecotoxicological relevance of the study, two toxicity tests were simultaneously performed: one with the salinity adjusted to the value of seawater in Portuguese Atlantic coast (test 1), and other without salinity adjustment (test 2). For both tests several seawater dilutions of the effluent were prepared. Since the purpose of the study was to use cholinesterase activity of M. galloprovincialis haemolymph as an ecotoxicological biomarker, the biochemical characterization of the forms present was performed. The results obtain indicated that the enzyme measured is acetylcholinesterase. LC50 values were 62.9% of effluent for test 1 and 70.5% for test 2. The values of EC50 for AChE inhibition were 83.1% and 52.3% of effluent, for test 1 and 2, respectively. The activity of GST was increased in the two tests. The results indicate that the urban effluent was toxic for M. galloprovincialis. Furthermore, these results show evidences for the presence of neurotoxic compounds, which may be detoxified through the formation of glutathione conjugates. Key words: Mytilus galloprovincialis, urban effluent, toxicity tests, biomarkers |
