Species-area patterns of benthic macro-invertebrates in Italian lagoons

The selection of adequate descriptors of the ecological status in aquatic ecosystem is a major requirement for the implementation of monitoring tools. It requires an analysis of the stress-independent sources of variation of potential descriptors, which need to be taken into account in the definition of ecosystem Typology and Classification. Here, we investigate at what extent the surface area of lagoons accounted for species richness of communities and body size abundance components. To this aim, the species-area and body size-area patterns of benthic macro-invertebrates were investigated in Italian lagoons. The analysis was based on a literature survey carried out considering a 30-year period from 1975 to 2004. Overall, 168 papers were selected, reporting taxonomic lists of benthic macro-invertebrates for 26 Italian lagoons, whose surface area ranged from few hectares to some hundreds of square kilometres. The analysis of published taxonomic lists recorded 1,055 taxa, belonging to 13 phyla, 106 orders and 351 families. Measures of standard body size for each of the 1,055 taxa were also obtained from published data as standard individual body length. Significant species-area relationships were observed at each level of taxonomic resolution considered, within dominant phyla (i.e. Arthropoda and Mollusca). Slopes of the power regressions were in the range of 0.11-0.24, increasing consistently with taxonomic resolution. Significant relationships were also observed by comparing the upper limit of the body size spectra to the surface area of the considered lagoons. Maximum body size-area relationships were described by power regressions with slopes in the range of 0.10-0.28. The observed species-area relationships underline the importance of physiographic characteristics of transitional water ecosystems in the identification of transitional water types, as required by the WFD. Moreover, the scaling of average taxonomic richness with lagoon surface, could also represent a standardisation tool for classifying the ecological status of transitional ecosystems. Finally, the patterns of body size area relationships would also have an important application to the field of monitoring transitional ecosystem health. © 2007 Springer Science+Business Media B.V.