Chamelea Gallina Research Articles

Ocean acidification will not affect the shell strength of juveniles of the commercial clam species Chamelea gallina: Implications of the local alkalinization of seawater

Ocean acidification (OA) is expected to decrease the strength of bivalves’ shells, especially during the early stages of development, with negative consequences to the resilience of natural populations and the economy. The objectives of the present study were to assess the long-term effect of increasing pCO2 after 217 days of exposure under controlled conditions of pH of ∼8.2, 8.0, and 7.7 on the strength and integrity of shells of juveniles of the commercial striped venus clam Chamelea gallina. Shell strength was estimated through compression tests and integrity through scanning electron microscopy (SEM) and dispersive X-ray analyses (EDX). The results showed that under increasing pCO2 the shell strength of juveniles is unaffected, which could be related to the locally elevated total alkalinity of seawater with respect to other parts of the coastal lagoon. However, despite this, it was also observed that the juvenile clams exposed to elevated pCO2 decreased their shell thickness and increased the porosity of their prismatic layer. Under future OA conditions, these changes could eventually compromise the integrity of the shells, becoming more vulnerable to the attack of predators and breakable during fishing operations. Future studies should address the plasticity of the organisms and the effect of the alkalinization of seawater on the resilience of shellfish juveniles under global change conditions.

Damage assessment on the discarded macro-benthic fauna in the Italian striped venus clam (Chamelea gallina) fisheries

The striped venus clam fishery in Italy is carried out by means of hydraulic dredges and it is one of the most important socio- economic activities in the Italian fisheries sector. Dredging has traditionally been considered among fishing activities with the greatest impact at the ecosystem level. Here, therefore, we investigated the disturbance level exerted by dredging on the studied area. Also, damage and mortality rates exerted by dredging on the discarded macro-benthic fauna living associated with Chamelea gallina during the summer season were investigated using a four-level damage scale, given three different haul time duration (3, 6 and 9 minutes). Despite the fact that macro-benthic fauna represented on average only 4.4% of the total catch, the most represented taxa in terms of both abundance and number were Malacostraca, Bivalvia, and Echinoidea. The analysis of the macro-benthic communities’ structure between hauls revealed that the species composition was very similar, and ABC plots together with the Warwick Statistics (W) revealed a moderately disturbed macro-benthic community. No significant difference was found in damage and mortality rates between hauls duration when stratified at taxon or species level. Overall, 61.0% of individuals of the catch were undamaged, whereas 16.1%, 3.7%, and 19.2% displayed slight, intermediate, and severe damage, respectively. We found that soft-shelled or soft-bodied species were the most affected by the harvesting process, whereas thick-shelled or thick-bodied species suffered the slightest damage. In particular, the species suffering major (severe) damage were the sea urchin Echinocardium cordatum (84.6%), the bivalves Mactra stultorum and Polititapes aureus (32.5% and 20.0%, respectively), the crab Liocarcinus vernalis (4.0%), and the sea star Astropecten irregularis (4.8%). The overall mortality rate of all discarded individuals was 22.9%, with E. cordatum showing the highest mortality rate of 96.0%. These findings highlight the importance of guaranteeing the integrity of the entire ecosystem through the adoption of suitable management plans and actions.

Influence of environmental conditions on the abundance of the striped venus Chamelea gallina in the northern Alboran Sea (Western Mediterranean Sea)

Environmental conditions can easily modulate the abundance of short-lived species, including those of commercial interest. These effects can occur during key periods of their life cycle, such as the spawning and recruitment periods, which are crucial for the stability of natural populations. This study attempts to elucidate the effects of abiotic factors on an important commercial species for artisanal fisheries in the northern Alboran Sea, Chamelea gallina, using CPUE data covering a 16-year period (2004–2020). Generalised Additive Models (GAM) were used to study how the abundance of the species was influenced by a set of environmental variables (sea surface temperature, sea surface salinity, phytoplankton, dissolved oxygen, North Atlantic Oscillation index and pluviometry) at spatial and temporal scale, as well as the spatio-temporal variation considering two areas (eastern and western areas) with different oceanographic conditions. The analysis showed that the abundance of C. gallina showed fluctuations over the historical time series in this ecoregion. The largest catches are observed in the western sector of the northern Alboran Sea, where the local sediment characteristics are more suitable for the species occurrence and the upwelling effect is more pronounced. Results showed that the most influential variables in the abundances during the spawning period were sea temperature, salinity and dissolved oxygen while during the recruitment period were only salinity and dissolved oxygen. Studies on the effects of environmental variables on the life cycle of species are essential to understand complex biological processes such as the spawning and recruitment, especially in commercially exploited species and in highly dynamic environments as the Alboran Sea.

A sea of change: Tracing parasitic dynamics through the past millennia in the northern Adriatic, Italy

Abstract Our study uses data from Holocene core samples and modern death assemblages to understand how human-induced environmental change in the northern Adriatic Sea (Italy) may have affected parasite-host dynamics in the economically important bivalve Chamelea gallina. Thirty-one radiocarbon dates confirm temporal distinctness between the periods before and after the onset of significant human influence and confirm that trematode prevalence has decreased by an order of magnitude over the past ~2 k.y. The median number of parasite-induced pits per bivalve host and parasite aggregation has also decreased significantly, signaling a substantial decrease in the effective population size of digenean trematodes. Gaussian finite mixture modeling of pit size does not support the hypothesis of parasite extinction. Combined, these results indicate the (potentially ongoing) collapse of parasite-host interactions in C. gallina in concert with human influence on the Adriatic and its transition to an “urban sea.”

Microplastic accumulation and ecological impacts on benthic invertebrates: Insights from a microcosm experiment

Microplastic (MP) pollution poses a global concern, especially for benthic invertebrates. This one-month study investigated the accumulation of small MP polymers (polypropylene and polyester resin, 3–500 μm, 250 μg L−1) in benthic invertebrates and on one alga species. Results revealed species-specific preferences for MP size and type, driven by ingestion, adhesion, or avoidance behaviours. Polyester resin accumulated in Mytilus galloprovincialis, Chamelea gallina, Hexaplex trunculus, and Paranemonia cinerea, while polypropylene accumulated on Ulva rigida. Over time, MP accumulation decreased in count but not size, averaging 6.2 ± 5.0 particles per individual after a month. MP were mainly found inside of the organisms, especially in the gut, gills, and gonads and externally adherent MP ranged from 11 to 35 % of the total. Biochemical energy assessments after two weeks of MP exposure indicated energy gains for water column species but energy loss for sediment-associated species, highlighting the susceptibility of infaunal benthic communities to MP contamination.

Effects of Temperature and Salinity on the LMS (Lysosomal Membrane Stability) Biomarker in Clams Donax trunculus and Chamelea gallina

Population of clams Donax trunculus and Chamelea gallina have been declining significantly in recent decades, and environmental pollution and accelerated global warming have been proposed as contributing factors to this decline, in addition to overfishing. Lysosomal membrane stability (LMS) is a sensitive indicator of health status of the organisms. In this study, we investigate the LMS in these species after exposure for 21 days to nine combined conditions of water temperature (12, 20, and 27.5 °C) and salinity ranges (27–28, 32–33, and 37–38). LMS was assessed in living hemocytes by using the neutral red retention assay. Mortality and the condition index of the organisms were evaluated as supporting parameters. The results indicated interspecies differences in the LMS under similar environmental conditions. Overall, LMS was found to be more sensitive to temperature than to salinity changes. Although both species can tolerate changes in either salinity or temperature seawater conditions, the tolerance range is narrower for D. trunculus, showing a significant cytotoxicity (NRRT < 50 min) at temperatures above 27.5 °C and salinities above 32, and 100% mortality at 27.5 °C and a low salinity range (27–28). This study is the first to assess the combined effect of temperature and salinity on the LMS in C. gallina and D. trunculus, and provide necessary information before using LMS as contaminant-related biomarker in field studies with these species.

Fluctuations in abundance of the striped venus clam Chamelea gallina in the southern Adriatic Sea (Central Mediterranean Sea): knowledge, gaps and insights for ecosystem-based fishery management

An assessment on the fluctuations in abundance of the striped venus clam (Chamelea gallina) in the southern Adriatic Sea (Central Mediterranean Sea), and the northern Gargano area, has been conducted through both historical information and recent data from monitoring surveys during the period 1997–2019. Production trends, conditions of the commercial stock biomass, and depth distribution pattern of juveniles and commercial sizes were analysed testing temporal differences. Moreover, the exploitation of the clam beds and recruitment events were investigated in 2018–2019. Changes in abundance were analysed using non-parametric tests for both juvenile (length class, LC < 22 mm) and commercial (LC ≥ 22 mm) fractions. Hydrodynamic changes, temperature and salinity variations were explored using a 3D hydrodynamic numerical model (MIKE 3 FM-HD) and statistical analysis, as well as changes in benthic assemblages impacted by hydraulic dredges were investigated through PERMANOVA and other multivariate analysis.The results showed a temporal decline of production and biomass of C. gallina during the 1997–2019 period, and a regression of the depth limit in the clams’ distribution towards shallower waters. A significant reduction in juveniles was observed during 2018–2019 with a very limited recruitment. The fishing exploitation showed high impacts on the commercial stock and benthic assemblages in the summer of 2018. Overall, water currents were predominantly directed offshore in 2018, during the C. gallina spawning period. This could affect the larval dispersal and settlement on unsuitable bottoms. Anomalies in temperature (high peaks in August 2018, > 28 °C) and salinity (low values in spring 2018, < 37 PSU) could have induced stress and mortality events on the entire clam bed in the study area. This first study highlights the need to integrate environmental information in the assessment of commercial stocks of clams in the Adriatic Sea, to better understand climate change effects on the fluctuations and to support effective ecosystem-based fishery management.

Stearate-Coated Biogenic Calcium Carbonate from Waste Seashells: A Sustainable Plastic Filler.

Waste seashells from aquaculture are a massive source of biogenic calcium carbonate (bCC) that can be a potential substitute for ground calcium carbonate and precipitated calcium carbonate. These last materials find several applications in industry after a surface coating with hydrophobic molecules, with stearate as the most used. Here, we investigate for the first time the capability of aqueous stearate dispersions to coat bCC powders from seashells of market-relevant mollusc aquaculture species, namely the oyster Crassostrea gigas, the scallop Pecten jacobaeus, and the clam Chamelea gallina. The chemical-physical features of bCC were extensively characterized by different analytical techniques. The results of stearate adsorption experiments showed that the oyster shell powder, which is the bCC with a higher content of the organic matrix, showed the highest adsorption capability (about 23 wt % compared to 10 wt % of geogenic calcite). These results agree with the mechanism proposed in the literature in which stearate adsorption mainly involves the formation of calcium stearate micelles in the dispersion before the physical adsorption. The coated bCC from oyster shells was also tested as fillers in an ethylene vinyl acetate compound used for the preparation of shoe soles. The obtained compound showed better mechanical performance than the one prepared using ground calcium. In conclusion, we can state that bCC can replace ground and precipitated calcium carbonate and has a higher stearate adsorbing capability. Moreover, they represent an environmentally friendly and sustainable source of calcium carbonate that organisms produce by high biological control over composition, polymorphism, and crystal texture. These features can be exploited for applications in fields where calcium carbonate with selected features is required.

Valorization of bio‐calcium carbonate based Chamelea gallina shell waste fillers in shape memory polymer composites

AbstractIn recent years, the focus has been on the use of calcium carbonate‐based seashell wastes in the production of new thermoplastic and thermoset polymer materials, paving the way for their use as biofillers in polymeric composites. In this study, it is aimed to obtain a new polymeric composite material by doping Chamelea gallina shells, on polylactic acid (PLA)/polyethylene glycol (PEG) blend. Structural characterization of the obtained PLA/PEG blend/C. gallina composite films was performed with attenuated total reflection infrared spectroscopy (ATR‐IR). When the thermal properties of composite materials were examined by thermogravimetric analysis (TGA), it was determined that the thermal stability of polymeric composites increased with the addition of C. gallina. SEM images showed that the polymer blend films, which appeared to have a porous structure, filled the pores with increasing C. gallina ratio. It was observed that the biodegradability of PLA/PEG blend composite films decreased with increasing C. gallina shells addition. However, C. gallina had a positive effect on the swelling and water absorption capacities of polymeric composites. The increase in tensile strength and elongation at break values of PLA/PEG blend/C. gallina composite films with increasing C. gallina means that the mechanical properties of the polymer are improved.

Influence of hydraulic clam dredging and seasonal environmental changes on macro-benthic communities in the Southern Adriatic (Central Mediterranean Sea)

Macro-benthic communities on the shallowest soft bottoms are impacted by hydraulic dredgers used for the harvesting of the striped venus clam (Chamelea gallina). Changes in macro-benthic assemblages were analysed across four areas in the Southern Adriatic Sea (Central Mediterranean Sea) during the winter and summer 2022 (low and high fishing pressures, respectively). Two sampling surveys were carried out collecting abundance data (N/100m2) of 69 species. Diversity indices (Shannon–Weiner and Equitability) were calculated and differences between seasons and areas were tested using non-parametric tests. Changes in the assemblage and feeding habits were explored by adopting permutational multivariate analysis of variance on 34 species. Moreover, environmental conditions of all areas in the two seasons were characterized by a set of 8 variables. Seasonal changes in diversity were only detected for the Shannon–Weiner index, with values significantly higher in winter than summer. Macro-benthic assemblages differed between the two seasons, and the winter assemblages were well-distinct in each area. In contrast, a high overlap was shown in the summer assemblages of the four areas. Changes in feeding habits showed an increase in filter feeding polychaetes and opportunistic/scavenger species during the summer. Temperature, Salinity and primary production were positively correlated to summer stations indicating potential thermic stress on the assemblages. The results provide information on the benthic community impacted by dredge disturbance and seasonal changes driven by environmental conditions, stressing the need to integrate these aspects in assessments on the health status of marine ecosystems required by European directives and fishery management plans.

Nanocrystalline and Amorphous Calcium Carbonate from Waste Seashells by Ball Milling Mechanochemistry Processes.

Nanocrystalline calcium carbonate (CaCO3) and amorphous CaCO3 (ACC) are materials of increasing technological interest. Nowadays, they are mainly synthetically produced by wet reactions using CaCO3 reagents in the presence of stabilizers. However, it has recently been discovered that ACC can be produced by ball milling calcite. Calcite and/or aragonite are the mineral phases of mollusk shells, which are formed from ACC precursors. Here, we investigated the possibility to convert, on a potentially industrial scale, the biogenic CaCO3 (bCC) from waste mollusk seashells into nanocrystalline CaCO3 and ACC. Waste seashells from the aquaculture species, namely oysters (Crassostrea gigas, low-Mg calcite), scallops (Pecten jacobaeus, medium-Mg calcite), and clams (Chamelea gallina, aragonite) were used. The ball milling process was carried out by using different dispersing solvents and potential ACC stabilizers. Structural, morphological, and spectroscopic characterization techniques were used. The results showed that the mechanochemical process produced a reduction of the crystalline domain sizes and formation of ACC domains, which coexisted in microsized aggregates. Interestingly, bCC behaved differently from the geogenic CaCO3 (gCC), and upon long milling times (24 h), the ACC reconverted into crystalline phases. The aging in diverse environments of mechanochemically treated bCC produced a mixture of calcite and aragonite in a species-specific mass ratio, while the ACC from gCC converted only into calcite. In conclusion, this research showed that bCC can produce nanocrystalline CaCO3 and ACC composites or mixtures having species-specific features. These materials can enlarge the already wide fields of applications of CaCO3, which span from medical to material science.

Microbiome variation at the clam-sediment interface may explain changes in local productivity of Chamelea gallina in the North Adriatic sea

BackgroundThe clam Chamelea gallina is an ecologically and economically important marine species in the Northwestern Adriatic Sea, which currently suffers from occasional, and still unexplained, widespread mortality events. In order to provide some glimpses in this direction, this study explores the connections between microbiome variations at the clam-sediment interface and the nutritional status of clams collected at four Italian production sites along the Emilia Romagna coast, with different mortality incidence, higher in the Northern sites and lower in the Southern sites.ResultsAccording to our findings, each production site showed a peculiar microbiome arrangement at the clam-sediment interface, with features that clearly differentiate the Northern and Southern sites, with the latter also being associated with a better nutritional status of the animal. Interestingly, the C. gallina digestive gland microbiome from the Southern sites was enriched in some health-promoting microbiome components, capable of supplying the host with essential nutrients and defensive molecules. Furthermore, in experiments conducted under controlled conditions in aquaria, we provided preliminary evidence of the prebiotic action of sediments from the Southern sites, allowing to boost the acquisition of previously identified health-promoting components of the digestive gland microbiome by clams from the Northern sites.ConclusionsTaken together, our findings may help define innovative microbiome-based management strategies for the preservation of the productivity of C. gallina clams in the Adriatic Sea, through the identification and maintenance of a probiotic niche at the animal-sediment interface.

The invasive mollusk Rapana venosa (Mollusca: Neogastropoda: Muricidae) in the mid-southern Black Sea: Distribution, growth, and stock structure

The rapa whelk, Rapana venosa (Valenciennes, 1846), known also as the veined rapa whelk or the Asian rapa whelk, settled in the Black Sea in 1940 and within the past 30 years has become an important economic contribution to local fishers along the coastline. This study examines the annual change in biomass, population structure, and interaction of the species with the ecosystem of rapa whelk in the mid-southern Black Sea. The samples were collected monthly in 2011 and 2012 by hydraulic dredge at different sites. Stock biomass was estimated at five different subregions and along four depth contours. In 2012 the biomass of rapa whelk increased significantly in in all subregions compared with the previous year sampling. Food availability is the main factor for species distribution, and in parallel, striped Venus clams, Chamelea gallina (Linnaeus, 1758), the main food source for rapa whelks, was significantly concentrated in the study area. The von Bertalanffy growth parameters (VBGP) were expressed as Lt = 121.78(1 − e−0.246(t + 0.33)). As a fisheries management point, our results highlight the overpopulation of rapa whelk in the region.

Mollusc &lt;i&gt;Anadara kagoshimensis&lt;/i&gt;, Allien Species, in Structures of the Benthic Communities on the Crimea Shelf

The frequency of occurrence of the mollusc-invader, Anadara kagoshimensis (Tokunaga, 1906), increased from 5 to 17–23% in zoobenthos of the South Coast of the Crimea Shelf for the last fifteen years. At the same time, the rate of the non-native mollusc was not significant and fluctuated: 0.73–23.29% from the biomass and 0.19–2.20% from abundance of the macrozoobenthos in the benthic communities. The mollusc A. kagoshimensis has been registered in the three communities: Chamelea gallina, Gouldia minima–Pitar rudis and Gouldia minima. The mollusc Anadara has not formed an independent community here. Influence of this alien species on bottom communities of the Crimean Coast was not such considerable as on bottom communities in northwest or in east parts of Black Sea Shelf. The structure of benthic communities had no significant changes on the shelf of the Southern Coast of the Crimea, compared with 70–80 of the last century. The first registration and the settlement of the mollusc-invader on the Crimea Shelf coincides with salinity decrease and temperature rise of coastal waters which are observed during last decade.

Spatial distribution patterns of striped venus clam (Chamelea gallina, L. 1758) natural beds in the Gulf of Cádiz (SW Spain): Influence of environmental variables and management considerations

Spatial distribution of characteristic population parameters (density, biomass and mean size) of Chamelea gallina were analyzed from systematic survey data applying a geostatistical approach in the Gulf of Cádiz (SW Spain). The influence of static (depth and distance to inland outflows), dynamic (sediment and water column features) environmental variables on density, biomass and mean size was also investigated. The global estimations of kriged density mean was 8.30 ind m−2, biomass mean was 23.78 g m−2, and mean size was 18.71 mm, with the species heterogeneously distributed along the whole sandy subtidal strip of the coast of Huelva. The resulting kriged map shows the location and extension of the patches (5 NM range) in the study area; where the highest density and biomass hot-spots were observed near the river mouths, except for the Guadiana River. This species was present from 3 to 16 m, but preferred the depth window between 6-8 m, having a density and biomass peak at approximately 7 m depth. A negative and significant correlation was found between density/biomass and the coefficient of variation of mean size suggesting a density-dependent process. The most influential factors on density and biomass were depth, sediment characteristics (grain size and percentage of organic content), distance from river mouths and waste water treatment plants, and sea bottom temperature. This study, in addition to reporting on the current status of these natural beds and the influence of dynamic and static environmental variables on their distribution, proposes an additional approach to estimating several biological parameters in C. gallina that could be valuable for the spatial management of this commercial resource and highlight the role of marine protected areas.

First data on the effect of Aluminium intake in Chamelea gallina of exploited stocks in the Southern Adriatic Sea (Central Mediterranean Sea)

The striped venus clam Chamelea gallina is an important shellfish resource in coastal area of Mediterranean Basin, playing a fundamental role in the ecosystems. In the last two decades there has been a reduction in the stocks of this bivalve with several mortality events along Adriatic Sea due to pollutants. Aiming to evaluate the effects on clams of the anthropogenic increase of some metals in the sea, we focused on aluminium. In particular, we tested whether Al could affect mucus secretion, since mucins are involved in protection from pathogens and toxicants and transport of alimentary particles and pseudofeces. Aluminium was administered in the form of aluminium chloride at concentrations of 25, 50 and 200 μM. Histochemical and lectin-histochemical - analyses were used to evaluate in situ qualitative and quantitative variation of the muciparous secretions produced by both the gills and foot epithelia. Treatments resulted in quali-quantitative alterations in the secretions of both gills and foot epithelia, in particular reduction of glycosylation resulting in a general decrease of acidic residuals and of mannosylated, glycosaminylated and fucosylated chains. This can result in a decrease of acidity and viscosity of mucus and thus it could affect its functionality and the survival of the animals.

Biochemical composition and reproductive cycle of the clam Chamelea gallina in the Northern Adriatic Sea: an after-10-year comparison of patterns and changes

The study of the relationships between growth patterns, energy reserves and reproduction, and their interdependency with environmental variables is crucial to increase the knowledge of the physiological processes regulating the recruitment and survival of commercially exploited bivalve species. In the present study, the biochemical profile and gametogenic cycle of the striped Venus clam Chamelea gallina monthly sampled in fishing grounds of the Chioggia district in 2001 and 2010 were investigated to identify possible variations that occurred after 10 years and to analyze inter-relationships among the biological parameters with changing environmental conditions. Our results indicated that higher phytoplankton availability and increased water temperature recorded from 2001 to 2010 resulted in higher reserve accumulation, mostly in the form of proteins, carbohydrates and glycogen. An increase was also observed in the calcification rate of the shells, which consequently became heavier in clams collected in 2010. Moreover, in 2010, as for the reproductive conditions, a prolonged spawning period was observed with respect to 2002. Overall results highlighted clear-cut differences in the physiological performances of clams collected in 2001 and 2010, suggesting the importance to monitor changes over time to unveil potential pros and cons for single populations of commercial interest.

Season- and sex-related variation in mucin secretions of the striped Venus clam, Chamelea gallina (Linnaeus, 1758) (Bivalvia: Veneridae)

An in situ analysis of mucin secretions along the annual cycle was performed on the striped Venus clam, Chamelea gallina. Individuals of both sexes from an exploited stock of Margherita di Savoia (Southern Adriatic Sea, Central Mediterranean Sea) were made in June 2020 and 2021, and in January 2021 and 2022, representative of summer and winter seasons, respectively. Tissues from the foot and the gills were analyzed for histochemical and lectin-histochemical analyses. Staining with Periodic Acid-Schiff, Alcian Blue pH 2.5 and High-Iron-Diamine indicated that mucins from both the foot and the gills were acidic, mostly sulfated. Lectin-binding analyses with PNA, SBA, WGA, LTA, UEA-I, AAA, SNA, MAA-II and ConA indicated the presence of N-acetyl-glycosaminylated, mannosylated and fucosylated residuals in the saccharidic chains. In the gills, the amount of acidic and glycosaminylated residuals was higher in summer in both sexes, whereas fucosylation was similar along the sampling period and mannosylation was never observed. In the foot, both surface epithelial and subepidermal secreting cells increased sulfation in winter in males, but not in females. Glycosaminylation and fucosylation were observed only in the surface cells of males. Mannosylated residuals were observed in all the foot cell types in both sexes. It is hypothesized that the observed qualitative and quantitative variations in mucin secretion is linked to the reproductive cycle.

Seasonal Variations in the Trace Elements and Mineral Profiles of the Bivalve Species, Mytilus galloprovincialis, Chamelea gallina and Donax trunculus, and Human Health Risk Assessment.

This study aimed to provide data on selected toxic (Cd, Pb and Ni), essential (Cr, Cu, Fe, Mn and Zn) and microelement (Na, K, Ca and Mg) concentrations in edible tissues of the Mediterranean mussel (Mytilus galloprovincialis), striped venus clam (Chamelea gallina) and the wedge clam (Donax trunculus). Samples were collected from the Black Sea (Bulgaria) four times over, a period of one year (2022). In comparison with the maximum permissible levels set by the EU and USFDA, all elemental concentration found in the bivalve species were lower than the prescribed limits. An estimation of the dietary metal intake through calculation of the target hazard quotients (THQ), hazard index (HI) and target risk (TR) was performed. The target hazard quotient (THQ) for individual metal and HI for combined metals were lower than 1, indicating no health risk for consumers due to the intake of either individual element or combined ones. The target risk value for toxic inorganic Pb and Cr was below 10-6, indicating no carcinogenic risk. According to these results, the consumption of these bivalve species is completely safe for human health.

Evaluation and quantification of shell damage and survival of the striped venus clam (Chamelea gallina) harvested by hydraulic dredges

The impact of hydraulic dredging on Chamelea gallina populations in the mid-western Adriatic Sea was assessed by evaluating and quantifying the damage exerted on harvested (non-sieved) and sorted (sieved by the mechanical vibrating sieve: commercial or discarded) individuals and by estimating the survival probability of discarded clams. The results showed that: i) dredging had a higher impact on determining shell damage than the mechanical vibrating sieve, ii) damage probability was strongly associated with shell length and in discard samples the effect of the shell length was greater due to the longer time spent by the individuals inside in the vibrating sieve before being rejected to the sea, iii) the survivability of the entire discarded fraction of clams was high. The findings support the Regulation (CE) 1380/2013 which foresees that discards from the Venus clam fishery must be returned to the sea and shall not be landed.