Quantitative information about spatial patterns in subtidal hard substrate assemblages is scant. Such information is necessary to understand the responses to anthropogenic disturbances in these habitats. Along the coast of Apulia (Southern Italy), the collection of the European date mussel Lithophaga lithophaga is a strong source of disturbance: harvesting is carried out by demolition of the rocky substrate and causes epibiota disappearance. A hierarchical sampling design was used to quantify the spatial variability of subtidal epibenthic assemblages and the extent of rock damage due to L. lithophaga harvesting along 360 km of rocky coasts in Apulia. The surveyed coast was divided into 8 adjacent sectors, and replicate samples were taken by visual inspection at each of the 3 sites nested in each sector. Multivariate analyses indicated that assemblages differed consistently with spatial scale, variability being higher at the largest scale. However, variability among sites within each sector was also detected. Patchiness (i.e., average similarity among quadrats) was consistent among sectors. Some species were identified as 'important' in characterising and/or differentiating sectors. The pattern of distribution of these species as well as total cover and number of species were analysed by analysis of variance. Results recorded a considerable source of variation at site level. Damage by L. lithophaga fishing was shown to be extremely widespread. A humped relationship between patchiness and disturbances by L. lithophaga fisheries was obtained. In particular, patchiness at a small scale was highest at 'intermediate' levels of damage, because disturbance produces patches of different size and/or age, leading to 'mosaic' landscapes of epibenthic assemblages.

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X-radiographs of corallites of the zooxanthellate coral Cladocora caespitosa (L.), collected in the Ligurian Sea bctween 3 and 27 m depth, were examined. C. caespitosa deposits 2 bands yr-'; the high density band is deposited during winter (November to March) while the low density band is deposited in summer. Average growth rates ranged from 1.36 L 0.58 to 4.42 i 1.61 mm yr-' No differences in the tirning of band deposition were found between shallow and deep colonies. A companson of the band pattern with monthly temperature-irradiance measurements from the Ligurian Sea, and with literature data on the photosynthetic efficiency of zooxanthellae, led us to hypothesise a mechanism of growth with a low dependency on autotrophy.

In the region of La Spezia (Ligurian Sea, Italy), the bryozoan Schzoporella errata forms sizeable buildups, termed 'giant colonies' or 'compound colonies' by previous investigators. Buildups were encrusting (up to 40 cm wide) with flat or bumpy surfaces in an exposed site, and erect (more than 20 cm high) branching anastornosed structures in a semi-exposed and in a sheltered site. The buildup architecture was significantly different in the 3 sites, with hlgher vertical development and number of branches per dm2 in the sheltered site. The internal structure of the buildups was also different: densely packed, extensive laminated sheets developed in the sheltered site; loosely packed, concentric sheets alternating with small cavities filled with sediment and shells of associated organisms were found in the semi-exposed and exposed sites. Functional groups could be recognised among the biota associated with S. errata buildups. The constructional pattern was interpreted as resulting from both interactions with other organisms and hydrodynamic conditions. While in the exposed site S. errata showed no vertical growth, in the sheltered site soft-bodied erect organisms formed the frame around which S. errata deposited a multilayered structure, which eventually caused the death and disappearance of the immured organisms. Breakage of branch tips by episodic disturbance and repeated binding through a complex array of budding patterns by S. errata resulted in tall buildups which preserved no trace of the soft-bodied organisms. Because of the role they played, these may therefore be defined as 'ghost frame-builders'. KEY WORDS: Bryozoa. Bioconstruction. Growth forms. Hydrodynamics. Associated biota. Mediterranean Sea

. Along the vertical cliff of Romito (Leghorn, Italy) 97 polychaete species were found from 0 to 6 m depth. Three depth related communities could be identified by trends in structural parameters (abundance, number of species, and diversity), by changes in species composition, and by the distribution of ecological and trophic groups. Such a zonation is consistent with the principal models proposed for the Méditerranean and seems mainly related to algal conditioning of the substrate.