Current status of macroinvertebrate methods used for assessing the quality of European marine waters: implementing the Water Framework Directive

This contribution reviews the current status of the macroinvertebrate methodologies proposed for European coastal and transitional waters under the Water Framework Directive (WFD), showing the weaknesses and strengths of the WFD implementation process and proposing future research topics and challenges. In total, 12 different methodologies have been officially accepted by European Member States (MSs). Most of these methods are multimetric, i.e. including several metrics into an equation, others are multivariate and some others are univariate. The methodologies vary in their use of the parameters included in the WFD (e.g. disturbance-sensitive species composition, richness, diversity, density, etc.), and they are described in this contribution. The results from the intercalibration undertaken by MSs are shown, including the boundaries between the quality classes, for each European eco-region and type. Finally, four areas in which scientific agreement is needed to satisfy future macroinvertebrate quality management are identified and discussed: (i) reduction of the present bewildering array of available indices by identifying the index approaches, components and formulations that are most widely successful; (ii) establishing minimum criteria for index validation processes that demonstrate index accuracy and reliability; (iii) comparing and intercalibrating methods to achieve uniform assessment scales across geographies and habitats and (iv) integrating indices across media and ecosystem elements.