Catálogo de publicaciones - libros

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 macroinvertebrates 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.

A new index was developed as a tool for quantifying the degree of disturbance in lagoons in order to meet the objective of Ecological Quality Status (EcoQ), using the zoobenthos quality element. The Index of Size distribution (ISD) is proposed to assess the ecological quality status of coastal lagoons. It represents the skewness of the distribution of individuals of a benthic community in geometric size (biomass) classes. The ISD was applied in three coastal lagoons with different levels of disturbance and classified them as of good, moderate and poor ecological quality. A scheme for the classification of EcoQ in lagoonal systems is presented. The index showed a strong relationship with the percentage of organic carbon in the sediment, as well as with the dissolved oxygen concentrations. ISD having the advantage of good discriminating power and not demanding high taxonomic resolution, could be a simple and promising tool to be further applied and tested in Mediterranean lagoons.

Allozymes and microsatellites were used to assess the level and distribution of genetic variation in grass goby population samples collected from the Venice Lagoon between October 2001 and May 2002. Eighteen enzymatic loci were examined in 434 individuals, 14 of which resulted to be monomorphic, and 4 (GPI-B*, LDH-B*, PGM-A*, PGM-B*) showed 2 alleles scored in 6 individuals only. Comparison with previous data suggests that genetic variation has been eliminated in the Venice Lagoon population during the last few years at three loci. In contrast, analysis of 11 microsatellites in a subset of 192 individuals revealed substantial molecular variation. Analysis of molecular variance showed a lack of genetic differentiation inside the lagoon with respect to site and date of collection, sex, and level of pollution. Significant variation in allelic frequencies was found at microsatellite loci when small (one year old) males were compared to large males (two and three years old), suggesting that a complex population dynamics occurs in this species. The very low level of polymorphism of allozymes could be due to the evolutionary history of the species, or, considering the difference between small and large males, could be the result of recent effects of drift. The second hypothesis is supported by the comparison with previous allozyme studies of the species in the same area, that suggests that loss of heterozygosity at three loci occurred in the last 10 years.

Feedbacks between plant biomass density and sedimentation maintain intertidal marshes in equilibrium with mean sea level (MSL). Stable marshes exist at an elevation that is supraoptimal for the biomass density of marsh macrophytes. At this elevation, biomass density is sensitive to changes in MSL, and adjustments in productivity and sedimentation rate help to maintain the marsh in a dynamic equilibrium with sea level, provided that the surface elevation remains within the supraoptimal range of the vegetation. The equilibrium elevation varies inversely with the rate of sea-level rise and directly with biomass density. It was also shown that a succession of intertidal plant communities depends upon the rate of sea level rise and the distribution of biomass density as a function of hydroperiod. Soft engineering solutions to coastal flooding could incorporate planting of marsh vegetation in the intertidal zone for the purpose of promoting sedimentation and dissipating wave energy. A successful design would employ plant species that have varying degrees of tolerance to flooding, maximum drag at their preferred depths, broad ranges within the intertidal zone, and that form a successional series.