Review of marine benthic indicators and metrics for the WFD and design of an optimized BEQI

In this report, indicators and metrics that have been developed and applied within the context of the Water Framework Directive have been reviewed. The goal of this review was to prepare the optimisation of the Dutch indicator for benthic quality. Indicators and metrics were evaluated by set-up, calibration and performance criteria and scored numerically by the authors of this report. This resulted in a ranking of indicators and metrics in each of the three WFD categories, with a highest (top 2) ranking for Shannon-Wiener and Margaleff's d in the category "diversity indicator", total density and abundance-biomass ratio in the category "abundance indicator" and AMBI and ITI in the category "sensitive/opportunistic species". The two best scoring (multi)metrics in this evaluation were DKI and the NQI, which make use of the best scoring indicators mentioned above. Suggestions are made for the composition of a new Dutch benthic quality metric, based on the best scoring indicators and metrics.