Coastal monitoring program of São Sebastião channel: Assessing the effects of ‘Tebar V’ oil spill on rocky shore populations

Due to a pipeline rupture on May 15th 1994, 2700 m3 of a crude oil reached the sea, affecting rocky shore communities, which have been monitored since 1993. These biological data, analysed by BACI approach, were integrated to chemical and toxicological analysis of the oil. Results of Studentʹs t-test did not indicate a significant difference between the percent cover average of the monitored populations (mussels and barnacles) from samples taken before and after the oil spill. The acute and chronic toxicity tests showed high toxicity of the oil. The lack of stress (i.e. mortality) on the populations can be mainly associated to: the sampling area was not highly contaminated despite the great amount of oil which reached surrounding areas; there were not enough physical (smothering) or chemical (toxicity) effects of the oil to alter the density of the populations which are considered moderately resistant to oil.