Quality assessment of benthic macroinvertebrates under the scope of WFD using BAT, the Benthic Assessment Tool Heliana Teixeira * , João Magalhães Neto, Joana Patrício, Helena Veríssimo, Rute Pinto, Fuensanta Salas, João Carlos Marques IMAR – Institute of Marine Research, c/o Department of Zoology, Faculty of Sciences and Technology, University of Coimbra, 3004-517 Coimbra, Portugal article info Keywords: WFD Ecological quality Benthic macroinvertebrates Transitional waters BAT abstract Assessing the health of ecosystems has become a focal point among researchers worldwide. Recently, the European Water Framework Directive intensified the development of approaches to assess ecosystems’ ecological quality. The Benthic Assessment Tool (BAT) is a multimetric approach to evaluate condition of subtidal soft bottom macroinvertebrates of coastal and transitional waters. The effects of anthropo- genic disturbances on benthic macroinvertebrate communities, from 1990 to 2006, allowed testing BAT performance in Mondego estuary (Portugal). The method was able to detect decrease on ecological quality, induced essentially by eutrophication and physical disturbances, and follow communities’ sub- sequent recovery. It evidenced, nevertheless, some limitations associated with the unstable nature of estuaries. The ecological classification of key species in the community and the balance expected between ecological groups of estuarine communities had great influence in the final ecological assess- ment. Shortcomings of the method were discussed in the light of its suitability for assessing transitional waters’ condition. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Under the scope of the European Water Framework Directive (WFD, 2000/60/EC), the assessment of the ecological quality of a water body must be based upon the status of different biological quality elements and supported by hydromorphological and phys- icochemical quality elements. The status of these elements is determined by the deviation they exhibit from the expected refer- ence conditions, at undisturbed or nearly undisturbed situations, specific for each type of water body (WFD, 2000/60/EC – annex V). Several tools, for coastal (CW) and transitional waters (TW), have been developed and successfully tested by EU Member States for the ecological assessment of different biological quality ele- ments: phytoplankton (Devlin et al., 2007; Revilla et al., 2009), angiosperms (Foden and de Jong, 2007; Romero et al., 2007; Garcia et al., 2009) and marine macroalgae (Ballesteros et al., 2007; Aré- valo et al., 2007; Wells et al., 2007; Juanes et al., 2008), benthic macroinvertebrates (Borja et al., 2000; Rosenberg et al., 2004; Muxika et al., 2007), and fish fauna (this element only for TW) (Breine et al., 2007; Coates et al., 2007). It is essential that outputs from different assessment methods result in equivalent quality levels for systems under the same ecological condition. This is a necessity underpinning the WFD intercalibration exercise and, therefore, EU Member States are required to compare their assess- ments and ensure that the metrics are calibrated (e.g. Buffagni et al., 2006; Borja et al., 2007; Ruellet and Dauvin, 2007; Carvalho et al., 2008). However, the first need is to ensure that assessment tools can successfully detect environmental oscillations caused by non-natural causes. Within estuarine systems it is more difficult to establish a stressor-response relationship using ecological indi- ces due to their natural variability (Wilson and Welkaim, 1992; El- liot and Quintino, 2007). The Benthic Assessment Tool (BAT), presented in this paper, was developed to assess ecological quality based on the macroinverte- brate fauna from subtidal soft bottoms. The tool includes a selection of metrics for abundance and composition of macroinver- tebrate fauna as required by the WFD and has been tested in Portu- guese CW and intercalibrated with other tools of the NEAGIG for CW (WFD NEAGIG, 2007). As for the BAT, most of the methods available were initially developed for marine habitats therefore the assess- ment of transitional systems requires an adaptation of the existent metrics to their natural dynamics (Dauvin, 2007). In a previous pa- per, Teixeira et al. (2008) concluded that after adjusting reference values of the metrics included in this method (Margalef index, Shan- non–Wiener index and AMBI) for estuarine natural gradients they presented significant differences for benthic communities under distinct anthropogenic pressures both spatially and temporally. The objective of this study was now to evaluate the indices joint performance in the BAT in assessing the ecological condition of 0025-326X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2009.06.006 * Corresponding author. Tel.: +351 239 836386; fax: + 351 239 823603. E-mail address: helianateixeira@ci.uc.pt (H. Teixeira). Marine Pollution Bulletin 58 (2009) 1477–1486 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul