The aim of the study was to evaluate the effectiveness of the application of multiple environmental descriptors through an asymmetrical sampling design to detect possible impacts related to the Costa Concordia event on the coastal marine environment. The Costa Concordia shipwreck occurred on a submerged rocky reef in the north-western Mediterranean Sea and the wreck was removed 2 years later. To achieve the proposed objective two main coastal ecosystems, the seagrass Posidonia oceanica and coralligenous assemblages were studied using two ecological indices, PREI and ESCA, respectively. Both indices show a lower ecological quality in the disturbed sites compared with the control ones. Differences between the disturbed and control sites observed in both studied ecosystems would seem to indicate an increase of turbidity around the shipwreck as the most plausible cause of impact. The concurrent use of different ecological indices and asymmetrical sampling designs allowed detection of differences in ecological quality of the disturbed sites compared with the controls. This approach may represent an interesting tool to be employed in impact evaluation studies.

The present study aimed at evaluating the influence of different gradients of disturbance on the structure of soft-bottom macroinvertebrate assemblages. The following hypotheses were tested: (i) the structure of benthic assemblages does not differ along a gradient of distance from a point-source of pollution; and (ii) this pattern was not influenced by the level of anthropogenic pressure that characterized the area. A combination of multivariate and univariate techniques was used to detect differences in the structure of assemblages among three areas characterized by different environmental conditions, among three distances from point sources of pollution within each area and in two different periods within one year. Differences among conditions in the structure of macroinvertebrate assemblages were evident independently from temporal changes. However, patterns of variability along gradients of disturbance were influenced by the environmental conditions of the studied areas. The total richness was similar in the three studied areas, while beta diversity showed patterns related to both area and distance from point sources of pollution. The results also underlined the suitability of multivariate analysis of the whole community to detect environmental changes.

Patterns of spatial and temporal variability of coastal fish assemblages were compared between areas subjected to different levels of protection at two different depths using a visual census technique. A no take reserve was compared with recreational fishing areas around a small Mediterranean island at 5 m and 20 m depth. Univariate and multivariate statistical techniques were used to test the hypothesis that protection could have different effects at different depths. A total of 56 species were identified during the survey. The most represented families were Sparidae and Labridae. Results showed an interaction between depth and levels of protection that was not persistent across the study period. This result was consistent for the whole fish assemblage and for the target species; most species showed higher abundance in protected areas at 20 m depth.

Variability in recovery of the introduced green alga Caulerpa racemosa has been investigated on a subtidal rocky shore in the north-western Mediterranean Sea. Two removal experiments were performed. The first was designed to test the effects of season on the early patterns of recovery of C. racemosa on a rocky bottom and on algal turf. In the second experiment recovery of C. racemosa on the rocky bottom and on algal turf was estimated from July–October 2000, the end of the vegetative period of the alga. Recovery of experimental plots occurred from adjacent populations of C. racemosa by stolon growth. In the first experiment, recovery occurred from August to November in all the experimental units, while no growth was observed during winter and spring. Recovery was significantly higher on algal turf than on rock during all vegetative periods. In both the habitats, recovery was quicker in summer than in autumn, even if differences between dates within each season were also significant. In the second experiment, three months after removal, the mean per cent cover of C. racemosa in algal turf was twice that on rock.

Macroalgal assemblages of Posidonia oceanica rhizomes of the western Mediterranean have been studied, in order to describe the structure of this community and to evaluate changes due to recent macroalgal invasions. To achieve these objectives, P. oceanica rhizomes were sampled from 21 beds distributed throughout the western Mediterranean Sea and macroalgal assemblages were studied using both species and functional groups as descriptors. Moreover, modifications linked to temporal fluctuations and depth were evaluated in an insular and in a continental bed. A total of 74 macroalgal species were found, among them 7 Chlorophyta, 8 Fucophyceae and 59 Rhodophyta. The species number varied from 5±0 at Vada to 18±0·58 at Panarea Island. The total percentage cover ranged from 19·5±1·8 at Cabo de Creus to 77·2±13·3 at La Maddalena Island. Filamentous species were dominant in the localities colonized by Acrothamnion preissii or Womersleyella setacea, while a high functional diversity occurred where the two introduced species were not present or they did not constitute dense turfs; the importance of crustose and foliose species was remarkable, while low cover of articulate and corticated-terete species was found at all localities. Localities where turfs were not developed were grouped together, even if they appeared more dispersed than those dominated by filamentous algae. The two beds studied over a 1 year period showed higher values of macroalgal cover in March and December, although significant differences were not detected with ANOVA in relation to either depth or season. The development of turfs, which occurs widely in western Mediterranean seagrass beds, seems to modify strongly the structure of macroalgal assemblages of rhizomes, mostly via the decrease in species and functional diversity.

Cold vapour atomic absorption spectrophotometry (CV-AAS) was used to evaluate total mercury concentrations in Posidonia oceanica, after initial mineralization of the samples in a microwave oven. Measurements were taken of three leaf tissue types: the adult leaf blade, the adult leaf sheath, and the intermediate leaf blade. Plants were sampled monthly over a one year period at two sites presenting different degrees of pollution: Rosignano (Tuscany, Italy) and Tonnara (Corsica, France).

The mercury concentrations recorded in the different P. oceanica tissues were systematically higher at the more contaminated of the two sites, thus confirming the value of this plant as a biological indicator. The mercury concentrations observed exhibit seasonal variations, with higher concentrations recorded in winter than in summer. These variations seemed to be negatively correlated to the plant's phenology. Also, the mean mercury concentrations were generally lower in young tissue (intermediate leaf blade) than in the older tissue (adult leaf blade).