Characterization of an undocumented CO2 hydrothermal vent system in the Mediterranean Sea: Implications for ocean acidification forecasting.

A previously undocumented shallow water hydrothermal field from Sicily (Southern Tyrrhenian Sea, Italy) is here described, based on a multidisciplinary investigation. The field, covering an area of nearly 8000 m2 and a depth from the surface to -5 m, was explored in June 2021 to characterise the main physico-chemical features of the water column, describe the bottom topography and features, and identify the main megabenthic and nektonic species. Twenty sites were investigated to characterise the carbonate system. Values of pH ranged between 7.84 and 8.04, ΩCa between 3.68 and 5.24 and ΩAr from 2.41 to 3.44. Geochemical analyses of hydrothermal gases revealed a dominance of CO2 (98.1%) together with small amounts of oxygen and reactive gases. Helium isotope ratios (R/Ra = 2.51) and δ13CCO2 suggest an inorganic origin of hydrothermal degassing of CO2 and the ascent of heat and deep-seated magmatic fluids to the surface. Visual census of fishes and megabenthos (mainly sessile organisms) allowed the identification of 64 species, four of which are protected by the SPA/BIO Protocol and two by the International Union for Conservation of Nature. The macroalgae Halopteris scoparia and Jania rubens and the sponge Sarcotragus sp. were the dominant taxa in the area, while among fishes Coris julis and Chromis chromis were the most abundant species. This preliminary investigation of San Giorgio vent field suggests that the site could be of interest and suitable for future experimental studies of ocean acidification.

Potential contamination and health risk assessment of heavy metals in Hurghada coastal sediments, Northwestern Red Sea.

Throughout the year, people flock to the Red Sea's shoreline for tourism and fishing. The current study aims to document heavy metal contamination and human health assessment in 30 surface sediment samples collected along the Hurghada shoreline in Egypt. To estimate sediment contamination, the pollution index (PI), pollution load index (PLI), degree of contamination (Cdeg), and Nemerow integrated pollution index (NIPI) were calculated, while the chronic daily intake (CDI), hazard index (HI), cancer risk (CR), and total lifetime cancer risk (LCR) were determined on both adults and children via ingestion, dermal, and inhalation pathways. The HM averages (µg/g dry weight) were in the following order: Fe (345.70) > Mn (49.36) > Pb (41.98) > Zn (7.47) > Ni (1.73) > Cu (1.23) > Co (1.09) > Cd (0.14). Pollution indices found that Hurghada coastal sediments were moderately polluted with Pb but not with the other HMs. The average CDI values were in the descending order of ingestion > dermal > inhalation pathways, and the average CDI values on children were higher than those on adults. The hazard index (HI) for adults and children was Pb > Ni > Cd > Fe > Mn > Co > Cu > Zn, and all values were <1.0, showing that these HMs had no substantial non-carcinogenic impacts on the human body. LCR results show that children have greater values than adults. LCR values in adults were lower than 1 × 10-6, indicating no substantial health concerns, while in children they ranged from 1 × 10-6 to 1 × 10-4, indicating no significant risk to human health.

Sanctuaries are not inviolable: Haplosporidium pinnae as responsible for the collapse of the Pinna nobilis population in Lake Faro (central Mediterranean).

The rapid spread of the protozoan Haplosporidium pinnae is having a strong negative effect on Pinna nobilis populations. A case study on a residual population in Lake Faro (Sicily, Central Mediterranean), whose long-term monitoring has revealed a dramatic decline following the 2018-2020 mass mortality event, is presented. In the framework of such monitoring, we performed tissue sampling on nine living P. nobilis, detecting the pathogen in seven of them. In contrast, other pathogens associated with P. nobilis disease in other areas, i.e., Mycobacterium spp. and Vibrio mediterranei, were not recorded. The surviving individuals (approximately twenty) showed that brackish areas only weakly mitigate the effects of H. pinnae disease and might not be resolutive. Nevertheless, the results show that Lake Faro may constitute one of the last Mediterranean P. nobilis sanctuaries.

Heavy metal pollution in surface sediments and human health assessment in southern Al-Khobar coast, Saudi Arabia.

Surface sediment samples from twenty-nine stations in south Al-Khobar coastline, Arabian Gulf, have been examined to assess the heavy metal contamination and impact on human health through dermal contact. The content in Cu, Zn, Cd, Pb, Fe, Mn, Co, Hg and Ni, was evaluated. Pollution index, modified degree of contamination, and pollution load index agreed to exclude heavy metal pollution. Differently, soil pollution index and Nemerow integrated pollution index pointed out moderate and heavy pollution grade for Hg and Cu, respectively. The human health assessment, according to the low values of the hazard index ˂ 1.0 for both adults and children, excluded any significant impact on the human body. The chronic daily intake and the total lifetime cancer risk also were consistent in excluding any risk to human health. Similarly, the carcinogenic risks for Pb and Cd, and the total cancer risk ˂1 × 10-6, did not imply significant health hazards.

A first insight into haemocytes of Pinctada imbricata radiata: A morpho-functional characterization.

The pearl oyster Pinctada imbricata radiata (Leach, 1814), from the Pacific Ocean, was one of the first species to reach via Suez the Mediterranean, colonizing the eastern basin and recently spreading to the western. The species showed to be able to adapt to a wide range of climatic, hydrological, and ecological conditions. Since 2000 it reached the Strait of Messina, where is now infesting the transitional waters of the oriented natural reserve "Laguna di Capo Peloro." Due to such resistance and adaptation ability, various assays were performed. Haemocyte morpho-functional aspects were evaluated in haemolymph samples fixed with 1% and 2% glutaraldehyde for optical and electron microscopy (TEM). The following assays were carried out: cell characterization using several dyes, detection of intra- and extracellular lipids, the capability of phagocytosis using the yeast Saccharomyces cerevisiae and to produce superoxide anion (O2- ). Detection of several enzymes, such as acid and alkaline phosphatase, arylsulfatase, chloro-acetylesterase and ß-glucuronidase was also assessed. Cell count was demonstrated to be abundant with a mean of 8.263 × 106 mm2 ± 0.935 × 106 (SD). Two main cell populations were noticed: granulocytes and hyalocytes, both competent for phagocytosis, to produce O2- , and characterized by lipids. Based on the granule analysis, enzymatic activity was also demonstrated. The observations under TEM confirmed all the results obtained. This study supports the hypothesis that P. imbricata radiata can be usefully employed as a model organism in environmental biomonitoring. Moreover, since the species represent potential threats to native species and ecosystems, further insights into its biological adaptations in invaded ecosystems are recommended.

Contamination and health risk assessment of arsenic and chromium in coastal sediments of Al-Khobar area, Arabian Gulf, Saudi Arabia.

The contamination and health risks by arsenic and chromium in the Al-Khobar coastal area, Arabian Gulf, have been assessed by examining 29 samples of surface sediment. Several single and complex indices were accounted to assess contamination, while the chronic daily intake (CDI), the hazard index (HI) and the total lifetime cancer risk (LCR) were applied to assess human health. The studied sediments showed absence or low level of As and Cr contamination. Results of CDI suggested a greater intake of As and Cr in children than in adults, mainly by ingestion pathway, reaching >99.5 % from the total for both adults and children. The recorded values of HI indicated not significant non-carcinogenic effects on the human body. LCR was higher in children than in adults. However, the recorded values suggested that the present carcinogenic risk for As and Cr can be considered acceptable or tolerable.

Identification of haemocytes and histological examination of gills of the spiny oyster Spondylus gaederopus (Linnaeus, 1758).

In the framework of investigations aimed to detect new available bioindicators in marine environment, haemolymph cells and ctenidia of the Mediterranean spiny oyster, Spondylus gaederopus, have been investigated. Haemocyte count and characterisation, phagocytosis and superoxide anion production and enzyme activity assays, have been carried out. TEM observations have been performed. After gross anatomy observations, cito-histological determinations have been carried out, especially focused on ctenidia structure and function. Main results concerned the relatively low number of circulating cells, and the rich in granules granulocytes, most of which were lysosomes. Release of lysosomal enzymes was confirmed a shared trait inside bivalves. Glycogen deposits as probable result of conversion of bacteria carbohydrates, have been detected, as well as the occurrence of both acidophilic and basophilic haemocytes. Phagocytosis, both in granulocytes and agranulocytes, has been recorded, together with the production of superoxide anion. Haemocytes were found positive to acid phosphatase, alkaline phosphatase, ß-glucuronidase, chloroacetylesterase and arylsulphatase. Ctenidia showed a complex organization, including two demibranch to each ctenidium, two different kinds of lamellae filament and specialized structures as ciliated disks connecting filaments in "eutherorhabdic ctenidia". The occurrence of three different types of mucous cells in the same region of ordinary filaments has been underlined. Such features, suggesting high resistance to environmental stress and disease, allow to consider spiny oysters as promising bioindicators, although deserving of further investigations to evaluate the physiological responses to stress in controlled conditions. Present data, moreover, providing basic information on the biology of S. gaederopus, notably implement the present knowledge on the Mediterranean spiny oysters, whose under-evaluated ecological role should be carefully considered.

Common patterns of functional and biotic indices in response to multiple stressors in marine harbours ecosystems.

Evaluating the effects of anthropogenic pressure on the marine environment is one of the focal objectives in identifying strategies for its use, conservation and restoration. In this paper, we assessed the effects of chemical pollutants, grain size and plastic litter on functional traits, biodiversity and biotic indices. The study was conducted on the benthic communities of three harbours in the central Mediterranean Sea: Malta, Augusta and Syracuse, subjected to different levels of anthropogenic stress (high, medium and low, respectively). Six traits were considered, subdivided into 22 categories: reproductive frequency, environmental position, mobility, life habit, feeding habit and bioturbation. Functional diversity indices analysed were: Functional Divergence, Quadratic Entropy, Functional Evenness and Functional Richness. To assess the trait responses to environmental gradients, we applied RLQ analysis, which considers simultaneously the relationship between three components: environmental data (R), species abundances (L) and species traits (Q). From our analyses, significant relationships (P-value = 0.0018 for permutation of samples, and P-value = 0.00027 for permutation of species) between functional traits and environmental data were highlighted. The trait categories significantly influenced by environmental variables were those representing feeding habits and mobility. In particular, the first category was influenced by chemical pollutants (organotin compounds and polycyclic aromatic hydrocarbons) and grain size (silt and sand), while the latter category was influenced only by chemical pollutants. Pearson correlations performed for functional vs biotic and diversity indices confirmed the validity of the chosen conceptual framework for harbour environments. Finally, linear models assessing the influence of stressors on functional parameters underlined the link between environmental data vs benthic and functional indices. Our results highlight the fact that functional trait analysis provides a useful and fast method for detecting in greater depth the effects of multiple stressors on functional diversity in marine ecosystems.

Tracking a mass mortality outbreak of pen shell Pinna nobilis populations: A collaborative effort of scientists and citizens.

A mass mortality event is devastating the populations of the endemic bivalve Pinna nobilis in the Mediterranean Sea from early autumn 2016. A newly described Haplosporidian endoparasite (Haplosporidium pinnae) is the most probable cause of this ecological catastrophe placing one of the largest bivalves of the world on the brink of extinction. As a pivotal step towards Pinna nobilis conservation, this contribution combines scientists and citizens' data to address the fast- and vast-dispersion and prevalence outbreaks of the pathogen. Therefore, the potential role of currents on parasite expansion was addressed by means of drift simulations of virtual particles in a high-resolution regional currents model. A generalized additive model was implemented to test if environmental factors could modulate the infection of Pinna nobilis populations. The results strongly suggest that the parasite has probably dispersed regionally by surface currents, and that the disease expression seems to be closely related to temperatures above 13.5 °C and to a salinity range between 36.5-39.7 psu. The most likely spread of the disease along the Mediterranean basin associated with scattered survival spots and very few survivors (potentially resistant individuals), point to a challenging scenario for conservation of the emblematic Pinna nobilis, which will require fast and strategic management measures and should make use of the essential role citizen science projects can play.

Relationships between plastic litter and chemical pollutants on benthic biodiversity.

Five Descriptors (D) of Marine Strategy Framework Directive (MSFD): marine litter (D10), non-indigenous species (D2) and organic and inorganic pollutants (D8), were estimated in a coastal area of GSA 16 (Augusta harbour, Central Mediterranean Sea) in order to study their effects on the biodiversity (D1) of the benthic community D6) and to improve data for the MSFD. Investigation of plastic debris had led to the identification of 38 fragments divided into four categories, among which microplastics resulted as the most abundant. Six non-indigenous species, belonging to Polychaeta (Kirkegaardia dorsobranchialis, Notomastus aberans, Pista unibranchia, Pseudonereis anomala, Branchiomma bairdi) and Mollusca (Brachidontes pharaonis) were found. Biodiversity and benthic indices suggested a generalised, slightly disturbed ecological status. Anthracene, Zinc and Chrome were the most abundant chemical compounds in analysed sediments. Significant correlations were found between the abundance of trace elements vs biotic indices and between plastic debris vs biodiversity and benthic indices. This study represents the first report about the abundance of plastic debris and its relationship to contaminants and infauna in Augusta harbour. Our results can provide useful information for national and international laws and directives.

Mapping toxic mineral contamination: the southern oyster drill, S. haemastoma (L., 1767), as evaluable sentinel species.

The nickel, chromium, arsenic, cadmium, and lead content have been evaluated, by ICP-MS, in digestive gland of the amphiatlantic gastropod Stramonita haemastoma, sampled along the highly anthropized Gulf of Milazzo (Central Mediterranean). Concentrations notably higher than those reported in literature for other Mediterranean Muricidae have been recorded. The results also indicated a different impact in different sites, according to distribution and typology of human activities, whilst recorded seasonal variations might relate with rapid metabolic response. Such preliminary results suggest S. haemastoma may be considered a promising sentinel species for inorganic contamination in marine environment, especially in terms of short-medium-term exposure.

Are shipwrecks a real hazard for the ecosystem in the Mediterranean Sea?

The aim of the present study was to evaluate the hazard from shipwrecks on communities by a holistic approach taking into account different effects on biological communities. Multibeam and Remotely Operated Vehicles surveys recorded ecological assessment of fish and benthic species on three shipwrecks flooded during the Second World War on Maërl beds habitats in the strait of Sicily. Pollution levels of a wide range of chemicals of ecotoxicological concern were also measured in sediments and in fish species from different trophic levels. Statistical analysis evidenced significant differences among pollutant levels between both sediments and fish collected in shipwreck sites and controls. Concerning fish, significant effects due to the vessel's cargo type and flooding position are recorded. In spite of that, our results underline that shipwrecks are also a hotspots of biodiversity and a habitat for preservation strategies in marine ecosystems that need to be monitored.

Ecological assessment of a heavily human-stressed area in the Gulf of Milazzo, Central Mediterranean Sea: an integrated study of biological, physical and chemical indicators.

Marine environmental disturbance can be assessed directly from physical and chemical parameters, or indirectly by the study of indicator species. In this study, an integrated approach to monitor the Gulf of Milazzo, labeled as a highly contaminated site, is presented. A total of 83 samples were collected from hard and soft bottoms in 2010. In sum, 2739 specimens belonging to 246 taxa, two first records for the Tyrrhenian Sea (Micronephthys stammeri and Nicomache lumbricalis) and three nonindigenous species (Brachidontes pharaonis, Crassostrea gigas and Notomastus aberans) were recorded. Biodiversity and biotic indices and their relationship with sediment parameters and the level of pollutants were assessed to describe faunal assemblage and evaluate environmental quality. Pearson tests evidenced significant negative correlation between polychlorinated biphenyls (PCBs) and specific richness (p<0.10). A comparison of the standard and recorded biotic values showed that M-AMBI seems to be the index more representative of ecological quality status (EcoQ) in the Gulf of Milazzo. No evident signs were highlighted on the complex.

Environmental quality assessment of Grand Harbour (Valletta, Maltese Islands): a case study of a busy harbour in the Central Mediterranean Sea.

Contamination levels by plastic debris, trace elements and persistent organic pollutants were assessed and related to macrobenthic diversity within soft bottoms of Grand Harbour (Malta, Central Mediterranean). Sediment toxicity was evaluated by ecotoxicological method, deploying Bacteria (Vibrio fischeri), Echinodermata (Paracentrotus lividus) and Crustacea (Corophium orientale). Univariate analysis (Pearson's test) was used to test relationships between biodiversity indices, pollutants and grain size. A multivariate approach (PERMANOVA) was applied to investigate for any significant differences among sampling stations concerning plastic abundances and to test the relationship between infaunal abundances and pollutant concentrations (the BIOENV test). Significant differences in the plastic abundances were found between sampling stations. The lowest value for Shannon-Wiener biodiversity index was associated to the highest sediment pollution level. Multivariate analyses suggest that MBT and TBT were factors that most influenced macrozoobenthic abundance and biodiversity. The bivalve Corbula gibba and the introduced polychaete Monticellina dorsobranchialis were the most abundant found species.