The Ecofunctional Quality Index (EQI): a new tool for assessing lagoonal ecosystem impairment.

A multimetric index for the evaluation of environmental quality (the ecofunctional quality index, EQI) has been developed using biotic data from three Italian coastal lagoons. Sampling programs were conducted between 1998 and 2000, on a yearly basis, with seasonal frequency at diverse sites in each lagoon of Po river Delta

The spread of an alien (Musculista senhousia, Bivalvia) in the Sacca di Goro lagoon (Adriatic Sea, Italy)

The Asian date mussel, Musculista senhousia (Mytilidae), which is endemic in western Pacific, appeared and become very abundant in the Sacca di Goro, a brackish lagoon in the Po River Delta (northern Adriatic Sea, Italy) in the early 1990s. The course of the invasion was documented through a macrobenthic monitoring program at three sites in the Sacca. From 1994, when the new mussel was first collected, M. senhousia spread throughout the lagoon, and, within a few years, reached densities exceeding 10000 individuals m-2. Mussel effects on biodiversity was assessed by comparing the macrobenthic community structure and composition: over a five yr-period some changes in the macrobenthic community seem to be apparent, suggesting a positive effect of the mussel on the number of species and benthic richness. Considering trophic guilds, positive significant correlations were highlighted between M. senhousia and detritivores and herbivores, while suspension feeders probably suffered competition from the date mussel. M. senhousia was initially successful because it exploited a naturally disturbed, sparsely occupied environment. The closely-dated documentation of the first collections, increasing abundance, and spread of M. senhousia at our study sites provided an opportunity to observe in progress a biological invasion of a habitat

Recovery of the macrobenthic community in the Valli di Comacchio, northern Adriatic Sea, Italy

The macrobenthic community structure of the Valli di Comacchio (northern Italy) was described in order to assess the ecological conditions of the main basins through 2001. In addition, the biotic data set gathered in 1997-1998 was compared to achieve an estimation of the eventual recovery of the lagoonal benthic assemblages. Four permanent sites (PI, M4, M5 and M6), located along a gradient of sediment texture and confinement, and representing four different areas of the lagoon, were sampled quarterly in 2001 for macrofauna and sedimentary variables (organic content, phytobenthic chlorophyll-a, depth of the redox potential discontinuity layer), and fortnightly for water variables (temperature, salinity, dissolved oxygen and planktonic chlorophyll-a). Water and sedimentary variables were typical of eutrophic areas. A total of 52 macrobenthic taxa were identified and, on the basis of the species collected, differences in faunal distribution among the four areas were recognized, although less marked than in previous studies. Sediment trophic status and its seasonal dynamics in the Valli were crucial in deter-mining species distribution among the different areas. The comparison between 1997-1998 and 2001 biotic data indicated that conditions in the lagoon had improved, especially in the formerly most impaired, central area. In the Valli di Comacchio, the recovery of benthic communities after severe disturbance will probably take longer, even if sewage discharges have been removed I I years ago. Secondary disturbance due to scarce water circulation, sharp temperature and salinity fluctuations, release of toxic substances from sediments influenced animal assemblages along spatial and temporal scales. The interplay of these variables probably caused deviations from the expected improvement in benthic conditions. Nevertheless, clear signs of amelioration, particularly at the previously most impaired area, were detectable.La structure de la communauté macrobenthique des Valli di Comachio est décrite pour définir les conditions écologiques des principaux bassins en 2001. Ces données sont comparées à celles de 1997–1998 pour mettre éventuellement en lumière une restauration de cet écosystème. Quatre stations permanentes localisées selon un gradient de texture sédimentaire et de confinement et représentant quatre aires différentes du système lagunaire ont été échantillonnées. Les mesures ont été effectuées chaque trimestre pour la macrofaune et le sédiment (contenu organique, chlorophylle a du phytobenthos, couche de discontinuité du potentiel redox) et chaque quinzaine pour la masse d’eau (température, salinité, oxygène dissous et chlorophylle a planctonique). Toutes ces variables sont caractéristiques d’aires eutrophes. Un total de 52 taxons a été identifié pour le macrobenthos. Des différences apparaissent entre les quatre zones quoique moins marquées que lors d’études précédentes. L’état trophique du sédiment et la dynamique saisonnière constituent des variables cruciales pour la distribution des espèces. Les conditions dans la lagune se sont améliorées depuis 1997–1998, particulièrement dans la zone centrale. Dans les Valli di Comachio, la restauration des communautés benthiques après une perturbation sévère demandera du temps, même si la décharge des effluents a été arrêtée il y a onze ans. Une perturbation secondaire due à la faiblesse de la circulation, aux variations brusques de température et de salinité et à l’apport de substances toxiques originaires du sédiment influence les communautés animales. Les interactions entre ces facteurs expliquent les déviations par rapport à la restauration espérée des conditions benthiques. Cependant, des signes clairs d’amélioration apparaissent, particulièrement dans la zone préalablement la plus altérée