Coralligenous reefs represent one of the key ecosystems of the Mediterranean Sea in terms of both species richness and habitat heterogeneity. Their main characteristic is the massive development of crustose macroalgae, the corallines, which form a bio-constructed basal layer. However, when growing on granitic substrates, these algae show a lower capacity to build thick concretions than those present on limestone. Assemblages developing on isolated granitic outcrops were investigated by scuba diving at 73 sites down to a depth of 56 m within the Tavolara-Punta Coda Cavallo Marine Protected Area (NE Sardinia, Mediterranean Sea). These outcrops were characterised by a scarce development of crustose corallines, due to the widespread presence of the brown algae Carpomitra costata and, to a lesser extent, Cystoseira zosteroides. Animal dominance increased with depth, mainly by sponges, in particular Axinella spp. and several species of Keratosa (Dysidea spp., Sarcotragus foetidus, Spongia lamella and S. officinalis). Gorgonians, which typically characterise the upper layer of coralligenous assemblages, were scarcely represented: Eunicella cavolini and E. verrucosa were generally rare, E. singularis was widespread, while Paramuricea clavata was comparatively frequent only at depth. All these features determined a peculiar community that was markedly different from the coralligenous assemblages occurring on neighbouring limestone rocks. Such a community, clearly characterised by the dearth of the typical biogenic hard substrate made by coralline algae, uneven distribution of gorgonians and, especially, the dominance of large and erect sponges, constitutes a distinctive facies of Mediterranean circalittoral communities worthy of conservation.

就物种丰富度和栖息地异质性而言，珊瑚礁是地中海的主要生态系统之一。它们的主要特征是硬壳大型藻类（珊瑚线）的大量发育，形成了生物构造的基础层。但是，当在花岗岩基质上生长时，这些藻类的浓密结石能力比石灰石上的藻类低。通过在Tavolara-Punta Coda Cavallo海洋保护区（北撒丁岛，地中海）内的73个位置进行潜水研究，研究了孤立的花岗岩露头上发育的组合，深度达56 m。这些露头的特征是由于褐藻Carpomitra costata的广泛存在而使甲壳珊瑚稀少发育，在较小程度上，Cystoseira zosteroides。动物的优势随着深度的增加而增加，主要是海绵，尤其是Axinella spp。和Keratosa的几种（Dysidea spp 。，Sarcotragus foetidus，Spongia lamella和S. officinalis）。典型地表现为珊瑚状组合体上层的高粱属动物几乎没有表现出来：Eunicella cavolini和E. verrucosa通常很少见，奇异E.广泛分布，而Paramuricea clavata只是在深度上比较频繁。所有这些特征确定了一个独特的群落，该群落与相邻石灰岩岩石上发生的珊瑚质组合明显不同。这种群落的明显特征是珊瑚藻类缺乏典型的生物成因硬质底物，戈尔贡人分布不均，尤其是大而直立的海绵的优势，构成了值得保护的地中海沿岸群落的独特相。