Many studies in marine coastal lagoons have focused on the marine-to-terrestrial gradient as a main source of variation for the structure of assemblages. In this paper, the magnitude of differences among locations arranged along the marine-to-terrestrial gradient of the western lagoon of Orbetello (Grosseto, Italy) was contrasted with the amount of spatial variability occurring among sets of locations that were not positioned along this axis. We propose that if the most important processes influencing assemblages were those associated with the external-internal gradient of the lagoon, as usually supposed, then assemblages should differ more among these locations than among any other locations. To test the above proposition, four locations arranged along the two major axes of the lagoon were established in November 2000. Each location was sampled three times (

The present study aimed at evaluating the effects of Caulerpa racemosa var. cylindracea spread on Mediterranean soft-bottom assemblages. The benthic assemblages colonized by C. racemosa were compared with non invaded assemblages at multiple spatial scales. In addition, a manipulative experiment has been conducted over a one-year period in order to compare the structure of native assemblages invaded by the alga with others where the alga has been manually removed and others that were not invaded. Results of both studies showed that Mediterranean soft-bottom assemblages invaded by C. racemosa differed from non invaded ones in terms of species composition, abundance and patterns of spatial variability. Moreover, in areas cleaned out from the alga, the benthic assemblages begin to recover their structure and after one year they get more similar to the assemblages observed in non invaded areas. The present paper, taking into account different aspects of C. racemosa invasion in Mediterranean soft bottoms, highlighted that the observed increase in alpha diversity did not correspond to an increase in the overall diversity of the studied system. Infact, the loss of beta diversity in invaded sites, together with the spread of species typical of vegetated habitats, may contribute to a homogenization of the Mediterranean coastal system. Furthermore, a possible role of ecosystem engineer for C. racemosa can be hypothesized.

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Macrobenthic communities in a commercial fishing ground (middle Adriatic Sea) exploited by otter trawling were compared with communities living in an area closed to fishing for over 10 years located near a gas platform. Our data highlighted significant differences in macrofaunal community structure between the two areas. In addition, the macrofaunal communities in the fished area displayed evidence of a higher level of stress compared with the other one. Several taxa reported in the literature as being sensitive to trawling (e.g., Ebalia tuberosa, Callianassa subterranea) were markedly more abundant in the area not affected by fishing. Macrofaunal community analysis using the index of multivariate dispersion and k-dominance curves provided evidence of stress in the fished area; however, it is not possible to predict whether the patterns observed will remain consistent over time based on only two temporal replicates. It is likely that the magnitude of the macrofaunal community response to fishing changes during the year according to season and fishing effort.