a b s t r a c tThe spatial distribution and structure of nematode assemblages in the area surrounding the harbour of Vado Ligure (Savona, NW Mediterranean) were studied in relation to the influence of natural and anthropogenic environmental factors. Stations were selected following an "anthropogenic gradient" from sites located near the city centre and its harbour to more pristine and distant sites. Sediment quality was determined by considering both sediment granulometric and chemical parameters (hydrocarbons, heavy metals, total organic matter, proteins, carbohydrates) as well as nematode abundance, diversity, life strategies, trophic structure and assemblage composition. A high correlation between environmental characteristics and the nematode response was found. On the basis of the comparison of these results, which identified three distinct sub-areas associated with different levels of environmental quality, a set of nematode indicator genera was selected for the future evaluation of quality status.

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The different components of the benthic community of a sandy microtidal beach (Arenzano) in Liguria (NW Mediterranean) were investigated during late spring (May) 2002 and. Sampling was carried out in two transects, chosen in order to represent the characteristics of the entire beach and their eventual spatial variations. Each transect included two stations: one placed in the swash zone (SW) and one in the surf zone (SF). Although no significant differences were found in the sediment texture over the 2 years (t-tests p > 0.1 for all the granulometric fractions), notwithstanding an increase in the mean grain size (from 0.8 to 1.1 mm) between the sampling periods, 2002 was characterised by a higher quantity of organic matter (on average 14.4 vs. 3.6 gC m )2 for the sum of proteins, carbohydrates and lipids) and higher bacterial biomass (on average 1.9 vs. 0.9 gC m )2 ). The metazoan assemblages (meiofauna and macrofauna) were also richer (density = 2.9 Â 10 5 vs. 1.0 Â 10 5 ind. m )2 , biomass = 0.09 vs. 0.03 gC m )2 for meiofauna; density = 1988 vs. 739 ind. m )2 , biomass = 0.14 vs. 0.03 gC m )2 for macrofauna) in 2002. A significant quantitative reduction (t-test for proteins, carbohydrates and lipids, at least p = 0.004) in the food supply in 2003 affected the abundance of the metazoans, as confirmed by a multivariate analysis that clearly differentiated the 2 years, and seemed to inhibit their relationships within the benthic food web. The bacterial biomass was always dominant, even under the least favourable trophic conditions, due to the ability of bacteria to adapt to a very harsh environment. Our results suggest that the food supply played an important role in the benthic community structures of the beach during late spring, bacteria being the key organisms within the benthic system. The communities seemed to be bottom-up controlled, while predation seemed to be irrelevant.

Meiofauna in sediments colonized by Posidonia oceanica in the Ligurian Sea (NW Mediterranean) was investigated to evaluate its use as an early warning indicator of environmental disturbance. Descriptors commonly used in seagrass health assessment are mainly related to the plant (e.g., phenological parameters) and/or to the meadow (e.g., structural parameters) and are subjected to long-term response times. Conversely, meiofauna is considered a good bioindicator with a rapid response to environmental variations, due to its main features (e.g., short life cycle, scarce mobility, presence/absence of tolerant/sensitive species). Meiofaunal community, sediment characteristics and organic matter descriptors in three meadows located in urbanized coastal areas were contrasted with those observed in three meadows located within Marine Protected Areas. Samplings were carried out in two distinct periods, at the beginning and at the end of the summer season, in order to individuate early changes in the meiofaunal assemblages. The meiofauna and, particularly, the nematode assemblage composition and diversity, highlighted differences among meadows at the end of the summer not detectable by organic matter descriptors and structural parameters of the meadow (e.g. shoot density). Nematodes are, thus, proposed as appropriate biological quality elements (BQEs) able to show early responses to environmental disturbance.

Meiofauna in sediments colonized by Posidonia oceanica in the Ligurian Sea (NW Mediterranean) was investigated to evaluate its use as an early warning indicator of environmental disturbance. Descriptors commonly used in seagrass health assessment are mainly related to the plant (e.g., phenological parameters) and/or to the meadow (e.g., structural parameters) and are subjected to long-term response times. Conversely, meiofauna is considered a good bioindicator with a rapid response to environmental variations, due to its main features (e.g., short life cycle, scarce mobility, presence/absence of tolerant/sensitive species). Meiofaunal community, sediment characteristics and organic matter descriptors in three meadows located in urbanized coastal areas were contrasted with those observed in three meadows located within Marine Protected Areas. Samplings were carried out in two distinct periods, at the beginning and at the end of the summer season, in order to individuate early changes in the meiofaunal assemblages. The meiofauna and, particularly, the nematode assemblage composition and diversity, highlighted differences among meadows at the end of the summer not detectable by organic matter descriptors and structural parameters of the meadow (e.g. shoot density). Nematodes are, thus, proposed as appropriate biological quality elements (BQEs) able to show early responses to environmental disturbance.