TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractDuring offshore activities directed at the exploration and production of hydrocarbons, the living conditions of the flora and fauna on the seabed may be disrupted. Drilling operations in particular, during which cuttings are discharged to sea, induce an impact on the benthic populations living in the sediment.The study described in this paper set out to assess directly on site the real impact of the cuttings discharged, the regenerating capacity of the ecosystem and the medium-and long-term recolonisation processes.The physical and chemical parameters used as tracers of the drilling muds were: the barium and hydrocarbon concentrations, and particle size.The paper presents the main results obtained from the monitoring surveys. It discusses the methodology adopted (study of the physico-chemical and biological quality of the sediment, plus evolution of toxicity and bacterial population trends). The study has shown that the relevant parameters for describing benthic macro-fauna are: species richness, abundance and diversity (Shannon index).Where the environment is concerned, the results obtained are a basis for evaluating the kinetics of restoration of the drilling site in time and in space, and provide evidence of the limited impact of the cuttings.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractDuring offshore activities directed at the exploration and production of hydrocarbons, the living conditions of the flora and fauna on the seabed may be disrupted. Drilling operations in particular, during which cuttings are discharged to sea, induce an impact on the benthic populations living in the sediment.The study described in this paper set out to assess directly on site the real impact of the cuttings discharged, the regenerating capacity of the ecosystem and the medium-and long-term recolonisation processes.The physical and chemical parameters used as tracers of the drilling muds were: the barium and hydrocarbon concentrations, and particle size.The paper presents the main results obtained from the monitoring surveys. It discusses the methodology adopted (study of the physico-chemical and biological quality of the sediment, plus evolution of toxicity and bacterial population trends). The study has shown that the relevant parameters for describing benthic macro-fauna are: species richness, abundance and diversity (Shannon index).Where the environment is concerned, the results obtained are a basis for evaluating the kinetics of restoration of the drilling site in time and in space, and provide evidence of the limited impact of the cuttings.

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