EUROPEAN SURFACE WATERS Application of an angiosperm-based classification system (BiPo) to Mediterranean coastal waters: using spatial analysis and data on metal contamination of plants in identifying sources of pressure Cecilia Lopez y Royo Cecilia Silvestri Maylis Salivas-Decaux Gerard Pergent Gianna Casazza Ó Springer Science+Business Media B.V. 2009 Abstract The Biotic Index based on Posido- nia oceanica (BiPo) is a classification system for evaluation of the ecological status in Mediterranean coastal waters, developed in accordance with the EU Water Framework requirements. The aim of this study is to verify the applicability and reliability of the BiPo index to different geographical areas of the north-western Mediterranean (France, Spain and Italy), to understand whether such a classification system may be applied more extensively, as so far it has only been applied to coastal waters in Corsica. The ecological status determined for sites is verified against pressures revealed from satellite imagery and from trace metal contamination of plants, to identify the sources of pressure that may be responsible for a low ecological status. The results of this study indicate that: (i) the BiPo index responds reliably to pressures, in different areas of the Mediterranean; (ii) sites with an ecological quality ratio (EQR) close to the good/moderate boundary require particular atten- tion to identify and reduce causes of deterioration; (iii) the support of chemical indicators, in this case metal contamination, is relevant to identify potential sources of pressure. Keywords Seagrass  Posidonia oceanica  Water Framework Directive  Ecological status  Mediterranean  Coastal waters Introduction The development and application of ecological indicators to assess the quality of aquatic environ- ments have been strongly addressed and stimulated in European waters by the adoption of the EU Water Framework Directive (WFD). The ecological quality objectives of the WFD (i.e. ‘good water status’ for all European waters by 2015) require water quality to be assessed using ecological indicators in priority (EC, 2000). This has lead to the development of WFD- compliant classification tools, based on the required biological quality elements. In coastal waters, these include phytoplankton (for which no fully compliant method has been developed at this stage), benthic invertebrates (Borja et al., 2000; Simboura & Zene- tos, 2002; Rosenberg et al., 2004), macroalgae (Panayotidis et al., 2004; Ballesteros et al., 2007; Wells et al., 2007; Juanes et al., 2008) and angiosperms Guest editors: P. No ˜ges, W. van de Bund, A. C. Cardoso, A. Solimini & A.-S. Heiskanen Assessment of the Ecological Status of European Surface Waters C. Lopez y Royo (&)  C. Silvestri  G. Casazza APAT - Agency for Environmental Protection and TS, Inland and Marine Waters Department, via Brancati 48, 00144 Rome, Italy e-mail: cecilia.lopezyroyo@apat.it C. Lopez y Royo  M. Salivas-Decaux  G. Pergent University of Corsica, Faculty of Sciences, 20250 Corte, France 123 Hydrobiologia DOI 10.1007/s10750-009-9880-z