Giovanni Santangelo

The Ligurian Sea: present status, problems and perspectives

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.

Distribution and assessment of marine debris in the deep Tyrrhenian Sea (NW Mediterranean Sea, Italy).

Marine debris is a recognized global ecological concern. Little is known about the extent of the problem in the Mediterranean Sea regarding litter distribution and its influence on deep rocky habitats. A quantitative assessment of debris present in the deep seafloor (30-300 m depth) was carried out in 26 areas off the coast of three Italian regions in the Tyrrhenian Sea, using a Remotely Operated Vehicle (ROV). The dominant type of debris (89%) was represented by fishing gears, mainly lines, while plastic objects were recorded only occasionally. Abundant quantities of gears were found on rocky banks in Sicily and Campania (0.09-0.12 debris m(-2)), proving intense fishing activity. Fifty-four percent of the recorded debris directly impacted benthic organisms, primarily gorgonians, followed by black corals and sponges. This work provides a first insight on the impact of marine debris in Mediterranean deep ecosystems and a valuable baseline for future comparisons.

Settlement and recruitment: The first stages in the life cycle of two epibenthic suspension feeders (Corallium rubrum and Anomia ephippium)

Abstract Studies on the population dynamics of the Mediterranean octocoral Corallium rubrum may prove extremely important for the conservation and management of this overexploited species. This study provides a detailed analysis of the settlement and recruitment processes in a red coral coastal population of the Eastern Ligurian Sea. Marble tiles, placed at two different depths (25 m and 35 m) were sampled photographically each month over two years, and the resulting densities of settlers were compared with those measured on the natural substrate. Red coral planulae successfully colonized tiles from August to September, showing a time‐limited recruitment. Contrary to red coral, Anomia ephippium, a bivalve that frequently colonizes tiles, exhibited a ‘pulsing’ recruitment throughout the year. Red coral settler density varied significantly between the different depths and times, while no statistical difference was found between artificial and natural substrates. As the tiles were permanent, they enabled us to follow the history of individuals and cohorts from settlement to their second year of life. Several mortality events affected settlers at both depths contemporaneously. In November 1999, the mass mortality that occurred in Ligurian shores also affected red coral settlers. These findings provide basic knowledge on the early phases of the red coral life cycle.

Molecular phylogeny of unculturable Karyorelictea (Alveolata, Ciliophora)

Karyorelictea is a class of traditionally unculturable ciliates characterized by a non‐dividing macronucleus. Their classification has been recently revised and morphological redescription of many species has been performed as well. On the contrary, molecular data of karyorelictean ciliates are largely underrepresented in public databases. In the present article we resumed and improved a method to characterize 18S rRNA gene sequences through direct amplification and sequencing of single cells. Using this approach, we characterized 12 different karyorelictean molecular operational taxonomic units (MOTUs: nine trachelocercids, one Geleia, one Remanella and one Loxodes), most of which were also photo‐recorded. These molecular data were used to reconstruct phylogenetic relationships among the three orders (Protostomatida, Loxodida and Protoheterotrichida) in which the class is traditionally subdivided. The most supported tree topology shows an association between orders Loxodida (Loxodes, Remanella) and Protoheterotrichida (Geleia), in contrast with previous works associating orders Loxodida and Protostomatida (trachelocercids) on a morphological basis.

Relationships between the spatial distribution of red coral Corallium rubrum and coexisting suspension feeders at Medas Islands Marine Protected Area (Spain)

Abstract (Received 13 December 2002 ‐ Accepted 26 May 2003) This paper addresses the spatial distribution of rocky bottom suspension feeders co-occurring in the same Mediterranean sciaphilic species assemblage, at Medas Islands Marine Protected Area (NE Spain), in which the octocoral Corallium rubrum is the most conspicuous component (in terms of cover area). One hundred and eighty photographic samples from 10 stations were examined. A significant negative association was found between the percent cover of C. rubrum and of the scleractinian cup coral Leptopsammia pruvoti. Nearest-Neighbour Distance (NND) analysis revealed a significant segregation between C. rubrum, L. pruvoti and Cystodites dellechiajei. This means that each species tends to have conspecifics as neighbours more frequently than other species. In only one station did red coral, once heavily harvested, exhibit low densities and no segregation. The asymmetric distribution of the NNDs between L. pruvoti and C. rubrum indicates that the patches of the former species are more homogeneously monospecific than that of the latter: in some cases L. pruvoti tends to wedge within crowded C. rubrum patches, but not vice versa. NNDs between red coral and L. pruvoti and between L. pruvoti conspecifics were greater than all the others. The in-traspecific NNDs of C. rubrum decreases significantly with its increasing percent cover while L. pruvoti does not reduce inter-individual NNDs also if its percent cover increases. Overall, these findings indicate the tendency of L. pruvoti and C. rubrum to segregate one from the other at small distances, and suggest that the spacing of L. pruvoti could be determined by the aggressive behaviour of this scleractinian.

Effects of increased mortality on gorgonian corals (Cnidaria, Octocorallia): different demographic features may lead affected populations to unexpected recovery and new equilibrium points

Over the last years, several marine populations suffered a drastic mortality increase of different origins; assessing the changes occurring in the demographic structure of such populations will allow evaluating their future trends and their ultimate fate. The aim of our research was to assess main demographic descriptors and related dynamics in populations of the Mediterranean gorgonians Paramuricea clavata and Corallium rubrum (the “precious red coral”) both subject to increased mortality, by life-history tables and Leslie-Lewis transition matrices. Gorgonian populations have been generally been considered to have low recruitment and low dynamics. Here, we test whether these features change when mortality rises and if such populations can reach new equilibria? Our findings show large differences between the two species examined, with lower recruitment and adult colony density, shorter life-span but over-abundant reproductive output in P. clavata. Recruitment density dependence was found in crowded populations of both species, albeit with different trends. Populations of both species tend to recover even after drastic mortality increase and P. clavata reaches a new equilibrium at lower densities than at pristine values, and this in a few years time. The findings in this review could shed some light on the poorly understood dynamics occurring in deep-water dwelling, affected populations of long-lived and slow-growing gorgonian corals.

The interstitial ciliate microcommunity of a Mediterranean sandy shore under differing hydrodynamic disturbances

Abstract The species assemblages of benthic ciliates from two adjacent locations at a sandy shore of the Ligurian Sea (Italy) are examined and compared. The environmental conditions are very similar, ex cept that one location is more exposed to hydrodynamic disturban ce than the other. Sediment samples (168 sandy samples from each station) for the identification and enumeration of ciliates were collected following a multifactorial sampling design under three dif ferent conditions: (1) a moderately perturbed spring‐ summer period; (2) an unusual one‐month‐long calm in spring; (3) an autumn‐winter period. Both stations showed a rich and well‐structured ciliate microcommunity. During the spring‐summer period, charac terized by highest ciliate density, 42 species, belonging to 27 genera, and 33 species belonging to 18 genera were found at the sheltered and exposed station, respectively. During this period, the exposed station harbours only a sub‐set of the ciliate assemblage living in the sheltered one. The t...

An overexploited Italian treasure: past and present distribution and exploitation of the precious red coral Corallium rubrum (L., 1758) (Cnidaria: Anthozoa)

Abstract The aim of this paper is to supply an overview of all historical and recent knowledge on landings, fishing and geographic distribution of the red coral banks along the Italian coasts in order to make a contribution to the conservation and future management of this resource. Along the Italian coasts, the banks have been exploited for millennia, using non-selective trawling gear that was banned in Europe in 1994. Today, harvesting is allowed only by scuba divers and regulated by specific laws. We examined 153 years of history of coral fishing in Italy, from Unification (1861) to 2014. Data about the coralline fleets and the amount of coral landings were recorded for the considered span of time. From a quantitative point of view, the coral fishing in Italy in the last 150 years has been dominated by the sub-fossil coral reservoirs from the Sciacca Banks (Sicily Channel), where an extraordinary amount of 18,000 tons was collected in 34 years (1875–1888 and 1893–1914). This amount represents about 90% of all red coral harvested along the Italian coast in the last 150 years. Excluding this period, the average annual yield was initially around 100 tons, decreasing to 28 tons 100 years later, therefore demonstrating a severe overexploitation of the resource. The great part of the deep red coral banks was abandoned because harvesting was no longer profitable. Nevertheless, quantitative data suggest that red coral banks, even though overexploited, are still widespread along Italian coasts, mainly in shallow waters. These banks show a remarkable persistence although with a generalised shift towards smaller colony sizes and higher density. The time span necessary in recovering the pristine structure, following the end of the fishing activities, appears very long and the populations of several areas might be unable to re-colonise the old and overexploited banks.

The interstitial ciliated protozoa of a Mediterranean microcommunity

The main features of an interstitial ciliate community, living in the coastal sand of the Mediterranean sea, were analyzed during a one-year survey, carried out on 113 samples. The community was composed of 56 species, 31 of which belong to 8 ‘resident’ genera. Total density varied from 0 to 410 individuals cm−3 and followed a Spring-Summer and an Autumn-Winter trend, not related to temperature or to any single abiotic variable (interstitial dissolved O2, grain sand size, salinity), although the density of some taxa was related to one abiotic factor. During Spring, diversity increased by a synchronous bloom involving the whole community. Some taxa, such as the predator Lacrymaria and its prey Frontonia, were significantly associated. The finding of the simultaneous bloom of congeneric species, like that of the genus Remanella suggests that they respond to the same environmental factors, and avoid interspecific competition.

Applying cathodically polarised substrata to the restoration of a high value coral

Larval settlement of the high value red coral, Corallium rubrum, was studied on three different CaCO3 substrata, viz. lithogenic (marble), electro-accreted calcium carbonate in the presence and in the absence of cathodic polarisation. The last two substrata consisted of stainless steel plates galvanically coupled with Zn anodes. The electrochemical characterization of the settlement device was studied in order to investigate correlations between cathodic parameters (polarisation potential, current density, calcareous deposit composition) and larval settlement. The results obtained in the natural habitat (at 35 m depth) showed that settlement was five times lower on the electro-accreted aragonite in the presence of low cathodic current densities (i ≤ 1 μA cm−2) compared to both marble tiles and electro-accreted aragonite in the absence of polarisation. These last two substrata showed similar settlement values. The implications of these findings on restoration strategies for C. rubrum are discussed.