Carbon and nitrogen isotope ratios (δ¹³C and δ¹⁵N) were determined in the zooxanthellae, host tissue, and whole symbiotic association of the symbiotic temperate coral Cladocora caespitosa, as well as in the different components of the coral's potential food sources (plankton, particulate organic matter in seawater and in the sediment). Data were collected both in winter and summer at three different locations, to assess the extent of auto‐ and heterotrophy in this species and get a better understanding of the functioning of temperate symbioses. There was a marked seasonal difference in the signature of the zooxanthellae and host tissue, highlighting two clear feeding patterns. In summer, δ¹³C signatures of the coral host and the zooxanthellae were similar (‐17‰) and very different from the signature of the food sources (from ‐21‰ to ‐25‰), suggesting that corals were relying on autotrophy for the acquisition of carbon. δ¹⁵N values also suggested that nitrogen was not acquired through feeding. Conversely, in winter, the δ¹³C signature of the host decreased by ca. ‐23‰ to ‐28‰, and was more comparable to the signature of the external food sources (between ‐24‰ and ‐25‰), suggesting a substantial reliance of C. caespitosa on external food sources during this season. There was also a 3‰ enrichment between the δ¹⁵N signatures of the food (4‐5‰) and the signature of the symbiotic association (7‐8‰), suggesting that nitrogen was also acquired through feeding. Overall, these results give evidence that C. caespitosa and temperate corals in general derive a large fraction of their energy from heterotrophic feeding in winter.

The Ligurian Sea is a deep basin in the northernmost sector of the western Mediterranean which shows peculiar hydrodynamic and meteo-oceanographic features. The coasts of the Ligurian Sea are among the most urbanised and industrialised along the Italian coastline: the main causes of disturbance being littoral urban development and harbour activities, the building of littoral rail- and highways, and the presence of several polluted discharges. This review, by evaluating the huge scientific output published in the last three decades, describes and discusses the most important geological, hydrological and biological characteristics of the Ligurian Sea. We show that this regional sea has largely been investigated in terms of its geological and structural evolution, as well as in terms of the sedimentation dynamics of the littoral and deep bottoms, with particular attention to the sedimentation balance of the beaches and their erosive processes. We report that the prevalent hydrodynamic and meteo-oceanographic conditions favour a continuous exchange of coastal water masses, and that the seasonal and interannual dynamics of water masses can effects the local climate, with direct and indirect consequences on fish and benthic communities documented in the last decade. We stress that although recent studies offer good knowledge of the distribution of coastal benthic communities, only scant information is available for the whole continental shelf, the submarine canyons and the rocky bathyal bottoms. Our meta-analysis reveals that significant fishing activities are monitored, but also that certain sectors of the biological resource are suffering, and suggests the set up of appropriate management measures. The Ligurian Sea hosts a number of Marine Protected Areas (MPAs) of high relevance, while the institution of the Whale Sanctuary completes the protection policy of the Regione Liguria. Our meta-analysis points out the need for long-term studies, based primarily on the analysis of those areas of the Ligurian Sea that have been little investigated to date. Finally, only properly addressed studies, using experimental approaches and along appropriate spatial and temporal scales, might allow us to understand the functioning of the Ligurian marine ecosystems, evaluate their health conditions and the dynamics of the main variables that affect the distribution of the single species (including species of high economic value) and benthic communities.