The Dredge Disposal Sediment Index (D2SI): A new specific multicriteria index to assess the impact of harbour sediment dumping

International audienceAt present, there are few operational indexes to assess the impact of a given human pressure taken alone. Nevertheless, the current challenge in the management of coastal marine environments in the framework of cumulative impacts and climatic change is to identify the relative contribution of each activity on ecosystem functioning. The objective of the present study is to propose an integrative approach to assess the environmental impacts of dumping operations, via the development of a new index, the Dredge Disposal Sediment Index (D2SI). From the selection of two types of station: impacted and unimpacted, D2SI integrates six sub-indices considering the biological and physical changes generated by dredge disposal on the seabed. A final score is proposed, according to the five classes of the European Water Framework Directive. The initial development of D2SI was conducted on the experimental dumping site of Machu (Bay of Seine), by applying a BACI (Before-After-Control-Impact) approach. An additional implementation (D2SI2) is used in the case of absence of data on ichthyofaunal or biological traits of life of macrobenthic fauna, which yields a comparable assessment of dumping pressure.In the future, the D2SI or D2SI2 indexes should be tested on other dumping sites with a view to comparing the assessment of this dumping activity