Typology in Mediterranean transitional waters: new challenges and perspectives

1. Transitional waters are ecotones between terrestrial, freshwater and marine ecosystems, being characterized by high spatial heterogeneity and temporal variability. 2. The EU Water Framework Directive (WFD) posed to the scientific community the challenge to classify these ecosystems into a small number of types, while retaining a functional classification of ecosystem types. 3. A niche theory approach is proposed to identify the limiting forcing factors organizing biological quality elements, i.e. the limiting niche dimensions. 4. The analysis of a macro-invertebrate dataset from published papers on 36 Italian lagoons suggested a two-level typological classification of Mediterranean lagoons. 5. Basic ecological theories, such as niche and island biogeography theories, have fundamental implications for the process of developing a typological classification for all aquatic ecosystems, as required by the WFD. Copyright (c) 2006 John Wiley & Sons, Ltd.