Ligurian Sea Research Articles

Anthropic Pressure on Cetaceans Stranded Along the Ligurian Coast Within the Pelagos Sanctuary: A Case Series

Data collected by C. Re. Di. Ma over a 3-year period (2020–2022) were considered to assess anthropic pressure on cetaceans living in the Ligurian sea. Out of a total of 37 stranded cetaceans, a complete post mortem examination was performed on 23 cases. Of these, 14 were further selected considering at least one of these conditions: (i) confirmed, probable, or suspected interaction with fishing activities through the application of a standardized diagnostic framework (7/14; 50%), (ii) toxicological stress through the evaluation of OCs hazardous levels (14/14; 100%), and (iii) terrestrial pathogen-associated disease (systemic infection and/or associated lesions) (7/14; 50%). For 9 animals out of a total of 14 selected, the cause of death was classified as natural (6/14; 42,8%), anthropic (3/14; 21,4%), or not determined (5/14; 35,7%) based on gross and histological pathology and ancillary testing. These findings extend our knowledge of the anthropic pressure to which cetaceans stranded along the Ligurian coastline are subjected from a multidisciplinary point of view.

A first vocal repertoire characterization of long-finned pilot whales (Globicephala melas) in the Mediterranean Sea: a machine learning approach.

The acoustic repertoires of long-finned pilot whales (Globicephala melas) in the Mediterranean Sea are poorly understood. This study aims to create a catalogue of calls, analyse acoustic parameters, and propose a classification tree for future research. An acoustic database was compiled using recordings from the Alboran Sea, Gulf of Lion and Ligurian Sea (Western Mediterranean Basin) between 2008 and 2022, totalling 640 calls. Using a deep neural network, the calls were clustered based on frequency contour similarities, leading to the identification of 40 distinct call types defining the local population's vocal repertoire. These categories encompass pulsed calls with varied complexities, from simplistic to highly intricate structures comprising multiple elements and segments. This study marks the initial documentation of the vocal catalogue of long-finned pilot whales in the Mediterranean Sea. Subsequent research should delve deeper into this multifaceted communication system and explore its potential linkages with social structures.

The Portofino Promontory: 200 Years of History of Marine Biology

This paper outlines the history of scientific research developed in the Portofino Promontory, located in the centre of the Ligurian Sea. The chronicles span over two centuries, from the late 18th century to the present day. Portofino is now recognised as one of the best-known areas in the world regarding marine biological communities and their temporal dynamics, particularly in relation to current climate changes. In addition, since 1999, with the establishment of the Marine Protected Area, significant research related to marine environment conservation has developed in Portofino. The role of the University of Genoa, the Natural History Museum, other important institutions, and the researchers involved in the Portofino area has been outlined.

The –WIND RISK project: nowcast and simulation of thunderstorm outflows

–WIND RISK is a research project dealing with measurement and modelling of wind fields within thunderstorm cumulonimbus clouds and outflows at the ground (i.e., downbursts and gust fronts). The general objective of the project is to advance the knowledge about the processes occurring inside thunderstorm clouds responsible for strong outflows, and the identification of the environmental (synoptic and meso-scale) conditions favourable to their development. The area under investigation is Northwestern Italy and the Ligurian Sea, which are among the most exposed regions to strong thunderstorms in Europe. Two measurement campaigns using Doppler weather radars and remote-sensing ground-based anemometry, and ad-hoc simulations using the WRF model are carried out to build a database of thunderstorm wind fields with special focus on downdraft and downburst characterization. All measurements and simulations are shared within the scientific community after the end of the project through datasets published on open access platforms.

New Documented Records of the Mesopelagic Fish Valenciennellus tripunctulatus (Sternoptychidae) in the Strait of Messina and a Review of Its Mediterranean Occurrences

The constellation fish, Valenciennellus tripunctulatus, is a small mesopelagic teleost typically found in equatorial and temperate waters worldwide, although the species has been also rarely recorded in the Mediterranean Sea (less than 20 specimens from the available literature since 1918). The Mediterranean records have been documented for the Strait of Messina, the southern Tyrrhenian Sea, the Ligurian Sea and the Adriatic Sea. The present paper offers an updated review on the occurrence of V. tripunctulatus in the Mediterranean basin and provides data on three new specimens, collected in the Strait of Messina between April 2010 and March 2024. Furthermore, we also report information from two individuals found in March 1992 and February 2017, respectively. Overall, the standard length of these specimens ranged from 24.1 to 28.2 mm, whereas weight varied from 0.18 g to 0.20 g. Morphometric and meristic data were reported, and this analysis revealed few differences between examined individuals in the number of PV (ventral series anterior to pelvic fin base) and AC (from anal fin origin to caudal fin base) photophore series. The relationship between total length and standard length (SL = 0.75 × TL + 2.98), total length and head length (HL = 0.17 × TL + 1.47) and standard length and head length (HL = 0.23 × SL + 0.88) showed high correlation values. Considering the lack of data on this species in the Mediterranean, updating morphometric, meristic, biological, ecological and distribution information is very important for taxonomic purposes and useful in understanding the characteristics of the regional population and eventual differences between Mediterranean stock(s) and those from other oceanic areas.

Forecasting the Mediterranean Sea marine heatwave of summer 2022

Abstract. Early warning of marine heatwaves requires short-term forecasts to provide precise information on timings, local-scale coverage, and intensities of coming events. Here, we describe our successful efforts to track the onset, peak, and decay of the Mediterranean Sea marine heatwave of summer 2022 with the Copernicus MedFS short-term (10 d) forecast system. First, we show that the 2022 event eclipses the economically and ecologically damaging event of 2003 in terms of marine heatwave (MHW) activity (a measure of intensity and duration). Forecasts of MHW area and activity provide a means of basin-wide validation, highlighting the capability of MedFS to capture regional behaviour. On local scales, we found that the MHW occurrence in the Ligurian Sea and Gulf of Taranto, two regions of economic and ecological importance, was also reliably forecast. Encouragingly, we note that the forecast has demonstrated skill in capturing not just the season-long MHW cycle but also breaks in MHW persistence and abrupt changes in local activity. Subseasonal forecasts do not yet demonstrate the capacity to predict MHW response to short-lived weather patterns, but this study confirms that short-term forecasts, at least in the Mediterranean Sea, can fill this gap.

Photobacterium damselae subsp. damselae in Stranded Cetaceans: A 6-Year Monitoring of the Ligurian Sea in Italy

Photobacterium damselae subsp. damselae (Pdd) is an increasingly common bacterium in post-mortem diagnostics of beached marine mammals, but little is known about its precise etiological responsibility. To estimate the prevalence of Pdd in stranded cetaceans from 2017 to 2022 on the Ligurian coast (Pelagos Sanctuary), we tested tissues from 53 stranded individuals belonging to four cetacean species. DNA extracts from cetacean tissue were screened using a polymerase chain reaction (PCR) assay targeting the Pdd ureC gene. Positive samples were screened by PCR for dly, hlyApl and hlyAch hemolysin genes, which were confirmed by sequencing. Twenty-two out of 53 (41.5%) cetaceans analyzed by PCR were confirmed for Pdd DNA in at least one tissue among those analyzed. Five of these cetaceans were positive for at least one of the hemolysin genes tested. In all Pdd-positive cetaceans, other pathogens that were considered responsible for the causa mortis of the animals were also found. The results provide new information on the spread of Pdd in cetaceans and support the thesis that Pdd might be an opportunistic agent that could contribute to worsening health conditions in subjects already compromised by other pathogens. However, further studies are needed to investigate and deepen this hypothesis.

Plasticizers levels in four fish species from the Ligurian Sea and Central Adriatic Sea (Mediterranean Sea) and potential risk for human consumption

Plastic materials contain additives such as plasticizers and flame retardants, which are not covalently bound to plastic polymers and can therefore be unintentionally released into the marine environment. This study investigated three families of compounds, phthalates (PAEs), organophosphate esters (OPEs), and non-phthalate plasticizers (NPPs) currently used as plastic additives, in 48 muscle samples of bogue (Boops boops), European hake (Merluccius merluccius), red mullet (Mullus barbatus), and European pilchard (Sardina pilchardus) sampled in the Central Adriatic and the Ligurian Seas. The additional goal of this study is to assess the potential risk to human health from fish consumption with the objective of determining whether the detected levels might potentially pose a concern. PAEs represent the majority of the plastic additives detected in the selected species, with ubiquitous distribution across the study areas, whereas for OPEs and NPPs, there is a more pronounced difference between the two study areas, suggesting that these compounds may represent different exposure levels in the two seas. Among PAEs, bis(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), and diisobutyl phthalate (DIBP) were the most abundant compounds, reaching levels up to 455 ng/g ww. OPEs were detected at higher concentrations in samples from the Ligurian Sea, and triethyl phosphate (TEP) was the most abundant compound. Among the NPPs, acetyl tributyl citrate (ATBC) was most frequently detected. From the results obtained, fish consumption may not pose a risk to human health (Hazard Quotient<1) but needs to be considered in future studies. Given the limited number of studies on PAEs, OPEs and NPPs in the Mediterranean Sea, further research is necessary to understand their potential bioaccumulation in marine organisms.

Unveiling near-inertial wave dynamics and storm-driven currents: Insights from moorings in the coastal Mediterranean Sea

This study presents comprehensive observations of currents and seawater properties (temperature, salinity and density) made with moored instruments on the continental slope in the eastern Ligurian Sea (Mediterranean) between 18 October and November 6, 2021. During this period, the depth of the surface mixed layer increased from 40 to 70 m. At the same time, near-inertial waves were consistently observed below the mixed layer. In particular, on 28 October, a depression in the mixed layer depth triggered the formation of a pronounced wave packet. This packet radiated downwards between 70 and 200 m and propagated southward. The wave packet had a vertical and horizontal wavelength of about 80 m and 150 km, respectively, an upward vertical phase speed of 100 m/d, a downward vertical group speed of 10–15 m/d, and a downward energy flux of 0.2–0.3 mW/m2. The observed frequency appeared subinertial, likely due to the red-shifting of the effective inertial frequency by the background vorticity. From 1 November, a storm with wind speeds of up to 15 m/s prevailed in the region. Near-inertial motion was pronounced throughout the water column and manifested itself as a first baroclinic mode. This mode exhibited a maximum isopycnal vertical displacement in the thermocline, accompanied by oscillatory currents that reversed with depth. Mainly superinertial currents were observed. The temperature and velocity data collected from all moorings indicated a southwestward propagation with a horizontal wavelength of about 200 km. While a slab model was partially successful in predicting inertial currents in the surface mixed layer, the storm-induced dynamics presented a challenge that was beyond the scope of the model.

Assessment of Octocoral‐Dominated Benthic Assemblages Along a Mesophotic Gradient, With a Focus on the Impact of Lost Fishing Gears

ABSTRACTCoralligenous, a typical Mediterranean mesophotic habitat, is a highly diverse assemblage, severely threatened by several stressors, including fishing litter. To characterise the coralligenous of the upper mesophotic of the Portofino Promontory (Ligurian Sea, Italy), video transects at 35 and 50 m depth were performed at four sites. Benthic assemblages and lost fishing gears were recorded, and the two depths compared. A higher coverage of taxa with complex 3D structures was found at 50 m, mainly due to the gorgonian Paramuricea clavata. However, the overall low density of this species (0.4–6.6 colonies/m2), together with the impact caused by 120 fishing lines found along the transects, highlights the need for tailored conservation measures. With climate change moving further down the water column and fishing impacts being a major cause of degradation, the design of marine protected areas needs to be extended to include mesophotic depths, contributing to the 30 × 30 targets agreed upon at the COP15.

Habitat shifts of the vulnerable crinoid Leptometra phalangium under climate change scenarios

Crinoid beds of Leptometra phalangium (Müller, 1841) have been identified as sensitive habitats by the General Fisheries Commission for the Mediterranean (GFCM) due to their high vulnerability to bottom trawl fisheries. Poorly resilient to physical damage, L. phalangium has been listed as a potential indicator of Vulnerable Marine Ecosystems (VMEs) in the Mediterranean Sea. If fishing activities represent the main cause of habitat destruction for this species, the ongoing changes in climate conditions may rapidly exacerbate the process. In this study, we developed an ensemble Species Distribution Modeling framework to predict the potential habitat of L. phalangium for present-days in the Mediterranean Sea, and used the model to infer potential changes in its spatial distribution by 2050 under two different climate scenarios (IPCC Representative Concentration Pathways RCP2.6 and RCP8.5). True presence-absence records were used and correlated to a parsimonious set of environmental predictors considered as important drivers of benthic species distribution. In present conditions, L. phalangium seems to be widely distributed along the continental slopes of the western and central Mediterranean. This crinoid is often described as confined to the continental shelf-break (100–200 m), but our results show that it can be found over a wider depth range, between 100 and 500 m. Our predictions obtained for the mid-21st century indicate an important habitat loss for L. phalangium under future climate conditions, mainly in the central and southern basins. Declines of 50 to 70 % in its suitable habitat were predicted under RCP2.6 and RCP8.5 compared to present-day predictions. Climate refugia (i.e., areas where environmental conditions remain suitable for the species in the future) were restricted to the northwestern basin (e.g., Gulf of Lion, the Catalan Sea, the Balearic Sea, Ligurian Sea) and in the southern Adriatic Sea. Provided by a robust statistical framework, climate refugia predictions, along with uncertainty assessments, must support the identification of priority areas for the conservation of VME indicator species by governmental bodies and regional management organizations.

Variation in the Health Status of the Mediterranean Gorgonian Forests: The Synergistic Effect of Marine Heat Waves and Fishing Activity.

Over the past thirty years, the red gorgonian Paramuricea clavata in the Mediterranean Sea has faced increasing threats, including heat waves and human activities such as artisanal and recreational fishing. Epibiosis on damaged gorgonian colonies is generally used as an indirect indication of stressed conditions. The density and height of P. clavata and the percentage of colonies affected by epibiosis and entangled in lost fishing gear were monitored to investigate the phenomenon and its trend over time in the Ligurian Sea. Analyses were based on transects collected during ROV campaigns between 2015 and 2022 at depths of 33-90 m. A strong correlation was observed between fishing efforts in the study area and the level of epibiosis. Maximal percentages of colonies affected by epibiosis and entanglement were recorded at depths of 50-70 m. Temporally, marine heat waves before 2019 were identified as the primary cause of damage to P. clavata. The decrease in epibiosis percentages after 2019, despite the 2022 heat wave, may be due to a quick recovery ability of the populations and a reduction in fishing activities during the COVID-19 lockdown in 2020. Long-term monitoring programmes are essential to understand the changes in marine benthic communities exposed to different stressors.

Fishing in the gene-pool: implementing trawl-associated eDNA metaprobe for large scale monitoring of fish assemblages

Marine biodiversity monitoring in the Mediterranean’s increasingly threatened ecosystems is crucial for effective ecosystem conservation and management. Here, we leveraged the Mediterranean International Trawl Survey program (MEDITS) to implement eDNA sampling through the recently tested ‘metaprobe’ procedure and characterize fish assemblages in three separate areas off the Italian coasts: Northern Adriatic Sea (NoAS), Ligurian and Northern Tyrrhenian Sea (LNTS), and Sardinian Sea (SaS). By combining the information from two homologous mitochondrial 12S metabarcodes––i.e., Elas02 and Tele02 targeting elasmobranchs and teleosts, respectively––we identified 108 species, over 60% of which overlapped with those caught by the trawl net. We produced an accurate reconstruction of fish community composition of the examined sites, reflecting differences in species assemblages linked with both geographic area and depth range. Metaprobe eDNA data consistently returned a biodiversity ‘bonus’ mostly consisting of pelagic taxa not captured through bottom trawl surveys, including rare and endangered taxa (e.g., elasmobranchs). Overall, the spatial characterisation of the assemblages across the surveyed areas was better delineated and more robust using eDNA metabarcoding than trawl data. Our results support the operationalisation of the metaprobe as a simple, inexpensive, versatile sampling tool, in association with pre-existing ship surveys, to overcome many of the limitations of marine data collection and strengthen marine management.

Diversity and dynamics of bacteria from iron-rich microbial mats and colonizers in the Mediterranean Sea (EMSO-Western Ligurian Sea Observatory): Focus on Zetaproteobacteria.

Autotrophic microaerophilic iron-oxidizing Zetaproteobacteria seem to play an important role in mineral weathering and metal corrosion in different environments. Here, we compare the bacterial and zetaproteobacterial communities of a mature iron-rich mat together with in situ incubations of different Fe-bearing materials at the EMSO-Ligure West seafloor observatory, which is located on the abyssal plain in the NW Mediterranean Sea. Our results on bacterial communities enable us to make a clear distinction between those growing on mild steel anthropic substrata and those developing on basaltic substrata. Moreover, on anthropic substrata we highlight an influence of mat age on the bacterial communities. Regarding zetaproteobacterial communities, our results point to an increase in ZetaOTUs abundance and diversification with the age of the mat. We corroborate the key role of the ZetaOTU 2 in mat construction, whatever the environment, the substrata on which they develop or the age of the mat. We also show that ZetaOTU 28 is specific to anthropogenic substrata. Finally, we demonstrate the advantage of using dPCR to precisely quantify very low abundant targets, as Zetaproteobacteria on our colonizers. Our study, also, allows to enrich our knowledge on the biogeography of Zetaproteobacteria, by adding new information on this class and their role in the Mediterranean Sea.

Assessment of OMA Gap-Filling Performances for Multiple and Single Coastal HF Radar Systems: Validation with Drifter Data in the Ligurian Sea

Assessment of OMA Gap-Filling Performances for Multiple and Single Coastal HF Radar Systems: Validation with Drifter Data in the Ligurian Sea

Habitat Fragmentation Enhances the Difference between Natural and Artificial Reefs in an Urban Marine Coastal Tract

Coastal urbanization and the consequent proliferation of artificial structures greatly impact rocky reef communities, productive and diverse marine environments that play a crucial role in the functioning of broader coastal ecosystems. This study, conducted along a 7 km stretch of coastline at increasing distance from the port of Genoa (Ligurian Sea), investigated whether the alternating presence of artificial and natural reefs leads to discernible differences in the biota inhabiting these two reef types. The study area is one of the most anthropized areas of the Mediterranean Sea, exhibiting nearly 60% coastal artificialization, which severely impacts coastal ecosystems, favouring the replacement of sensitive species with more tolerant species. Ten reefs (5 natural and 5 artificial) were surveyed by scuba diving at about a 6-m depth, employing quadrats of 50 cm × 50 cm to estimate visually the percent cover of conspicuous sessile organisms. The artificial reefs hosted a similar number of species (18) to their natural counterparts (19) but exhibited a distinct community composition: the former were especially characterized by Jania rubens and filamentous algae, with the latter characterized by Peyssonnelia squamaria and Mesophyllum lichenoides. This difference, however, became negligible where coastal habitat fragmentation (here measured with a purposely devised Fragmentation Index) was minimal. Reducing fragmentation may therefore represent a management strategy to minimize the potential impact of artificial structures on marine biodiversity.

From micro to mesoscale: Understanding the influence of macroalgal communities on Ostreopsis Schmidt blooms

Harmful Algal Blooms (HABs) are increasing in temperate areas, and the growth rates of benthic harmful dinoflagellates may be favoured in the context of global climate change. Benthic dinoflagellates, including species belonging to the Ostreopsis Schmidt genus, are known to develop on the surface of macroalgae and different macroalgal morphotypes and communities could host higher or lower cell abundances. The physical structure of the macroalgal substrate at the small scale (cm, microhabitat scale) and the structural complexity of the macroalgal community at the medium scale (few m, mesohabitat scale) could play a relevant role in bloom facilitation: the hypothesis that Ostreopsis species could be associated with macroalgal turfs and shrubs, structurally less complex communities than canopy-forming macroalgae, is especially under discussion and, if confirmed, could link bloom occurrence to regime shifts in temperate ecosystems. The present study, performed in two locations of the Ligurian Sea (Rochambeau, France and Vernazzola, Italy) aimed at understanding marine vegetation's role at the micro and mesohabitat scales in controlling the distribution and abundance of Ostreopsis. The abundance of the microalgal cells was quantified at different spatial scales, from cm to a few m, on different macroalgal species and communities, including artificial substrates, to tease apart the micro and mesohabitat effects. The results obtained show a high spatio-temporal variability, potentially hiding habitat-related patterns. The substrate's preferences diminish when cell abundances are very high, as in the case of Rochambeau, while in presence of moderate cell abundances as in Vernazzola or the first phases of blooms, it is possible to appreciate differences in abundances among substrates (in our study, Dictyota fasciola (Roth) Lamouroux supporting higher abundances). Our results open new research topics such as the study of blooms at a larger scale (macrohabitat) and testing different sampling methods to standardise the cells' abundances independently on the substrate.

Threatened cetaceans off the coast of Israel and long‐range movement of a sperm whale

Abstract Research in the western Mediterranean has shown that sperm (Physeter macrocephalus) and Cuvier's beaked whales (Ziphius cavirostris) are present as small, globally distinct populations that face numerous threats. The eastern Mediterranean is not well studied, and few surveys have investigated the composition of cetacean communities. In this study, visual‐acoustic surveys were conducted off the coast of Israel during April–May 2022 to characterize the cetacean community. Sperm whales (three encounters), Cuvier's beaked whales (one encounter), bottlenose dolphins (one encounter (Tursiops truncatus)) and unidentified delphinids (17 encounters) were acoustically detected. Sperm whales were foraging ~10 km off Haifa, at 370–1220 m deep and social vocalizations (codas) corresponded to the Mediterranean dialect. One immature male that was photographed is known from 12 previous encounters in the Ligurian Sea, indicating a west–east movement of approximately 2800 km. Automated passive acoustic monitoring of narrow, relatively shallow areas such as the Sicily Channel could provide an opportunity to reduce mortality of individuals making long‐distance movements within Mediterranean basins. Israeli waters provide habitat for cetaceans, with two threatened subpopulations—sperm and Cuvier's beaked whales—that are negatively impacted by anthropogenic activities, including those that introduce underwater noise. More data are needed on densities of these deep‐water species, and an evaluation of the threats faced in the wider Levantine basin.

Geohazard features of the Ligurian Sea

ABSTRACT We present the characterization of geohazard-related features of the Ligurian Sea with the map of its physiographic domains (1:250,000 scale) and five maps (1:100,000 scale) of the morphological and morpho-bathymetric elements. These were realized in the framework of the MaGIC (Marine Geohazard along Italian Coasts) project, promoted by the Italian Civil Protection Department. The characterization of submarine geohazards along continental margins, together with mapping of marine geological features are critical for the management of coastal risks. Multibeam bathymetric data combined with high-resolution 2D reflection seismic data, allowed to identify and map the main tectono-sedimentary features related to mass movements along the Ligurian continental margin. A dense grid of seismic profiles allowed to improve the comprehension of the margin structure as well as its recent tectonic activity providing new insights concerning mass wasting processes and active tectonics relationships to plan further, focalized investigations in areas of maximum risk.

Impact of river capture on erosion rates and offshore sedimentation revealed by geological and in situ 10Be cosmogenic data (Corsica, western Mediterranean)

Quantitative analysis of fluvial topography and sediment yield changes are often independently used to detect major river capture events and episodes of drainage reorganization. Here we use a unique set of geological and in situ 10Be cosmogenic data from Corsica, Western Mediterranean, to provide evidence of major river capture events affecting the former Paleo-Ostriconi river catchment during the Pliocene, and to illustrate how the landscape of Corsica is still reacting to the disequilibrium caused by the late Miocene uplift of Alpine Corsica. We found that ∼1280 km2 of basin area originally draining towards the Ligurian Sea were abruptly connected to the Tyrrhenian Sea by the capturing Tavignano and Golo rivers, which led to the formation of a large Pliocene-Quaternary submarine fan offshore the Tyrrhenian coast. The increased sediment yield towards the Tyrrhenian margin after river capture in the Pliocene was three times greater than the average sediment yield in the same source-to-sink system during the Holocene (410±100 t·km−2·a−1 vs ∼131±8 t·km−2·a−1) and greater magnitude than any subsequent peaks in sediment yield during late Pleistocene glaciations. 10Be-derived denudation rates reveal that focused erosion still affects retreating knickpoints near the sites of former river capture in central Corsica, suggesting persistence of landscape disequilibrium for several millions of years. Our results demonstrate the potentially large impact of river capture on the stratigraphic record and highlight the importance of full consideration of landscape response times to onshore disturbances for any reliable interpretation of the offshore sedimentary archive.