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Sediment characteristics (Total organic carbon, C/N ratio, carbonates, grain size) and macrofaunal assemblages were studied in Sum- mer 2005 in 9 coastal lagoons of eastern Sicily (Italy) belonging to 3 study areas (Capo Peloro, Marinello and Vendicari). The diffe- rent ecosystems were selected upon their differences in geographical position, size, depth, water exchange, anthropic impact and expec- ted organic matter loading. The aim of this study was to explore the relationship between the Total organic carbon (TOC) content of se- diment and macrofaunal assemblages characteristics, as indicated by the Study Group on Benthic Indicators of IOC/UNESCO (http: //ioc.unesco.org/benthicindicators/). A total of 30813 specimens belonging to 51 families were collected and identified. Abun- dance (N), Family richness (F), Shannon (H') and Evenness (J') indexes were compared with sediment characteristics. Bioenv analysis and Pearson correlations have shown that grain size represents an important variable influencing the macrofaunal settlement. TOC ranged between 2 and 75 mg g -1. Coherently with previous studies on this topic, our results suggest that risk of reduced abundance and biodiversity due to organic loading in sediments of Sicilian coastal lagoons is low at TOC concentrations less than about 10 mg g -1, high at TOC concentrations greater than about 30 mg g-1 and intermediate at concentrations in between.

Marinello is a brackish area of notable naturalistic value, located in the Thyrrhenian coast of Sicily (Italy), characterised by strong geomorphologic changes. This ecosystem is particularly suitable for the study of ecological processes because of the high variability of environmental parameters on small space-time scale and the heterogeneity of coexisting habitants. In order to follow the evolution of Marinello ecosystem, the national research council-I.A.M.C. Messina (Italy) has performed several survey from 1978 until now. Here we summarize the main steps of our researches that lead us to know the evolution of this ecosystem.

In the present study the evolution of the benthic ecosystem of Oliveri-Tindari (Messina, northern coast of Sicily), is described through the examination of data collected every ten years, from 1978 up to now. In particular three cycles of investigations (1978, 1987, 1997) provided comparable information on the edaphic, trophic and biological characteristics of the area. As shown, there as been a constant rise in the fine sedimentation occurring in the pools during these twenty years. With regard to the trophic characteristics, a general decrease of the organic carbon content in the sediments was recorded in the second cycle of study. The trophic-sedimentary evolution caused marked changes in the structure of the benthic communities, as pointed out by the qualitative and quantitative variations. In general a decrease in the density of the mollusc benthic communities was observed, because of the progressive isolation of the pools.

An interdisciplinary research was carried out, during March 1997 around the Egadi Islands, to improve the knowledge on the oceanographic, trophic and sedimentologic features of this environment. Some results, relative to the more quick analysis (temperature, salinity, density, heterotrophic bacteria, proteolytic activity, bionomic and sedimentologic identification) are showed in This paper. These preliminary data led us to formulate a descriptive hypothesis about this ecosystem. A high salinity gradient, and a marked water stratification were found, which are probably responsible for local confinement of the trophic resources in the surface layers. Therefore in the southern part, the benthic communities are very poor, but toward the northern part, organic enrichment of the substratum and remarkable benthic assemblages were recorded. In the deepest part, a generalized oligotypic condition was observed.