What are the most suitable indices to detect the structural and functional changes of benthic community after a local and short-term disturbance?

Abstract : A one-year experimental study was conducted in 2012–2013 to assess the physical and biological impacts of dumping dredge spoil composed of muddy fine sand (1 million m3) in a benthic zone with medium-grained sands in the eastern part of the Bay of Seine. Previous study showed that the impact is local and the benthic habitats show a high degree of resilience after a short dumping phase and the recovery of the community is observed just after cessation of the disturbance. Moreover, during the deposition phase, Impacted and Influenced zones can be distinguished from a Non-impacted zone. A combination of indices (BO2A, AMBI benthic indices) and modelling tools were applied to study the dumping dredge spoil impact. Results highlighted that these different indices allowed detecting the dumping operations effects. In addition, results from the AMBI et BO2A indices revealed that the system showed a high resilience after a short dumping phase. Lastly, the macrofauna and demersal fishes appear to be stimulated in the Influenced zone during the dumping phase, thus supporting the Intermediate Disturbance Hypothesis.