Health concerns of consuming cockles (Cerastoderma edule L.) from a low contaminated coastal system

Effects of wildfire ash on the fatty acid and sugar profiles of bivalves - A comparative study of a freshwater and a marine species

Wildfires can impact both freshwater and marine ecosystems through post-fire runoff, but its effects on bivalves, particularly those living in marine habitats, remain largely overlooked. While evidence exists that wildfire ash can alter the fatty acid (FA) and sugar profiles of aquatic biota, its influence on the biochemical profiles of bivalves have not been addressed to date. This study aimed to assess the effects of ash exposure on the FA and sugar profiles of two bivalve species used for human consumption: a freshwater clam (Corbicula fluminea) and a marine bivalve (Cerastoderma edule), additionally evaluating potential effects on their nutritional value. Both species were exposed to environmentally relevant concentrations of aqueous extracts of Eucalypt ash (AEAs) for 96 h. Results showed species-specific responses to ash extracts exposure, with more pronounced effects on C. edule. This species exhibited a trend for reduced FA content, statistically significant for C17:0 but also evident for unsaturated FAs, which is relevant for human health as they represent a decrease in the nutritional value. Conversely, an increase in the sugar content of this species was observed with increasing AEA concentrations, despite only statistically significant for galactose and xylose. In contrast, the clams exhibited only minor effects, showing a trend for increased FA and decreased sugar contents, but only significant for the monounsaturated FA content. This study suggests a higher sensitivity of marine bivalves to wildfire ash compared to their freshwater counterparts. Moreover, it highlights, for the first time, the potential of post-fire runoff to alter the biochemical profiles of bivalve species, raising concerns about broader impacts on aquatic trophic webs and human health, an issue that becomes particularly relevant given the forecasted increase in wildfire's frequency and extension due to global warming.

Partitioning of metals in the tissues and cytosolic fraction of Cerastoderma edule

The concentrations of Cd, Cu and Zn have been determined in the tissues and the cytosolic fraction of the common cockle, Cerastoderma edule, collected from sediments in the Tamar, Plym and Avon estuaries (South West, England). Metal concentrations in the tissues of C. edule from the Avon were lower than those from the Tamar and Plym, except for Cu in the digestive gland. Significant statistical relationships were only obtained between the total sedimentary metal concentrations and Cd in the body of C. edule and Cu in the digestive gland. The cytosolic fraction was extracted from each of the tissues and separated for protein analysis thereby allowing determination of the metal contents in high molecular weight (HMW) compounds, metallothionein-like proteins (MTLP) and very low molecular weight (VLMW) compounds. The digestive glands of C. edule from the Avon had relatively low concentrations of MTLP, whereas MTLP concentrations in the digestive gland of cockles from the Tamar and Plym were higher. The cytosolic fraction of C. edule had relatively low total Cd and Cu concentrations associated with MTLP, whereas Zn was preferentially associated with the HMW and the VLMW components. The results are relevant to metal distributions in C. edule and the role of cytosols in the management of metals by C. edule and other invertebrates.

Accumulation characteristics of metals in human breast milk and association with dietary intake in northeastern China

The trace elements present in breast milk play a vital role in the growth and development of infants. Nevertheless, numerous studies have reported the presence of toxic metal contamination in breast milk from various countries and regions, which poses potential risks to breastfed infants. This article aimed to investigate the characteristics of trace elements in breast milk and explore the relationship between breast milk and diet in Dalian, a coastal city in northeastern China. Breast milk samples and representative local food samples were collected from Dalian for research. The results revealed that 57 % of breast milk samples significantly exceeded the WHO safety limit (0.6 μg/L) for arsenic, with a measured mean value of 0.96 μg/L. Moreover, the levels of chromium (mean value: 2.63 μg/L) in 34 % of breast milk samples exceed the WHO recommended safety level (chromium: 1.5 μg/L). Aquatic foods accounted for 60 % to 90 % of the total intake of arsenic, cadmium, vanadium, mercury, and lead. The Spearman correlation analysis demonstrated strong positive correlations among breast milk metal elements, including copper-zinc (r = 0.68) and nickel‑chromium (r = 0.89). Furthermore, the food-to-milk accumulation factors (FMAF) of strontium, nickel, arsenic, vanadium, cadmium, and mercury were relatively low (median values <0.005). While the FMAF values for chromium and lead were higher, with median values of 0.038 and 0.07, respectively. The results indicated potential risks of the toxic metal arsenic in breast milk from Dalian, China for breastfed infants. Therefore, continuous monitoring of breast milk for toxic metals and foodborne contamination is necessary.

Do Freshwater and Marine Bivalves Differ in Their Response to Wildfire Ash? Effects on the Antioxidant Defense System and Metal Body Burden

Wildfires constitute a source of contamination to both freshwater and marine ecosystems. This study aimed to compare the antioxidant defense response of the freshwater clam Corbicula fluminea and the marine cockle (Cerastoderma edule) to wildfire ash exposure and the concomitant metal body burden. Organisms were exposed to different concentrations (0%, 12.5%, 25%, 50%, and 100%) of aqueous extracts of Eucalypt ash (AEAs) from a moderate-to-high severity wildfire. The activity of various enzymes, as well as lipid peroxidation, protein content, and metal body burden, were determined after 96 h of exposure. A significant increase in the protein content of soft tissues was observed for C. edule at AEA concentrations ≥ 25%, unlike for C. fluminea. Similarly, significant effects on lipid peroxidation were observed for cockles, but not for clams. For both species, a significant effect in the total glutathione peroxidase activity was observed at AEA concentrations ≥ 25%. Relative to the control, AEAs-exposed clams showed higher Cd content, whereas AEAs-exposed cockles showed higher Cu content, thus exhibiting different responses to the exposure to wildfire ash. The susceptibility of bivalves to ashes, at environmentally relevant concentrations, raises concern about the effects of post-fire runoff to bivalve species.

Characterising contaminants distribution in marine-coastal sediments through multivariate and nonparametric statistical analyses: a complementary strategy supporting environmental monitoring and control

This work investigates a statistical approach analysing data from monitoring activities on marine-coastal areas for environmental quality determination and surveillance. Analyses were performed on a database of the Environmental Protection and Prevention Agency of the Puglia Region. As, Cr, Ni, and Pb concentration values in marine sediments and biota from 2013 to 2015 and 2017 were processed to investigate different contaminant characteristics. Hierarchical cluster analysis identified three contaminant distribution classes with (1) highest Cr, Ni, and Pb concentrations, (2) highest As concentration, and (3) lowest contaminants concentration. The Kruskal-Wallis and Friedman tests showed that contaminant distributions were statistically different when considering the monitoring years and classes. However, statistical similarities resulted during the 2013-2017 and 2014-2015 periods. Spearman's coefficients displayed positive correlations among the pollutants in each matrix and mainly negative correlations for matrices comparison. This methodology aims to provide a practical support for monitoring to identify potential environmental deterioration over time and correlations with specific contamination sources.

Interplay of Seasonality, Major and Trace Elements: Impacts on the Polychaete Diopatra neapolitana

Simple Summary

Coastal systems often serve as sinks for toxic elements, and seasonality has been responsible for many changes in the physical and chemical parameters of waters and sediments, leading to geochemical alterations in aquatic systems and the alteration of element uptake rates in organisms. Diopatra neapolitana worms were collected from five sites of the Ria de Aveiro lagoon in the autumn, winter, spring, and summer of 2018/2019 and were tested to check for differences in the biochemical responses (cell damage, antioxidant enzymes, biotransformation enzymes, and energy-related parameters) among seasons and sites. In general, the results demonstrated that enzyme activities were higher in spring and summer due to high temperatures and element bioaccumulation. Energy-related parameters presented with higher levels in spring and autumn, which was mainly due to element bioaccumulation. Oxidative damage was higher during winter and was related to salinity and decreases in temperature. This study demonstrated that abiotic factors influence the geochemistry of elements and that both significantly affect organism performance in low-contamination systems, such as the Ria de Aveiro lagoon. This knowledge is important to understand how ecological and economically relevant species such as D. neapolitana respond to environmental changes.

Abstract

Polychaetes are known to be good bioindicators of marine pollution, such as inorganic contamination. Major and trace elements are commonly present in sediment and may be accumulated by polychaetes such as the tubiculous Diopatra neapolitana. In this study, D. neapolitana individuals were collected in the autumn, winter, spring, and summer of 2018/2019 from the Ria de Aveiro lagoon (western Portugal) to understand how seasonality influences element accumulation. The impact of the interaction of seasonality and elements on oxidative status, energy metabolism, and oxidative damage was also assessed. The obtained results showed that the activity of the antioxidant enzymes catalase, glutathione S-transferases, and non-protein thiol levels were higher in summer and that superoxide dismutase, lipid peroxidation, and electron transport system activity increased in winter. The lowest glycogen levels were observed during spring, and protein carbonylation was the highest during autumn. These results could mainly be related to high temperatures and the bioaccumulation of Al, As, Mn, and Zn. Energy-related parameters increased during spring and autumn, mainly due to the bioaccumulation of the same elements during spring and summer. Lipid damage was higher during winter, which was mainly due to salinity and temperature decreases. Overall, this study demonstrates that seasonality plays a role in element accumulation by polychaetes and that both impact the oxidative status of D. neapolitana.

Sensing Cd(II) Using a Disposable Optical Sensor Based on a Schiff Base Immobilisation on a Polymer-Inclusion Membrane. Applications in Water and Art Paint Samples

A disposable colour-changeable optical sensor based on an interesting polymer inclusion-membrane (PIM) was designed to determine Cd(II) ions in aqueous medium. The Schiff base 2-acetylpyridine benzoylhydrazone (2-APBH) immobilised on the polymer membrane was used as a sensing molecule. The amounts of the PIM components were optimised by a 3² fractional factorial design with two central points and two blocks. The best optical sensor composition consisted of 2.5 g of poly(vinylchloride) (PVC) as a base polymer, 3 mL of tributyl phosphate (TBP) as a plasticiser, and 0.02 g of 2-APBH as a reagent. The sensor showed a good linear response in the range from 0.02 mg L⁻¹ (limit of detection) to 1 mg L⁻¹ of Cd(II) under the following experimental conditions: pH 9.5 (adjusted using ammonium chloride buffer solution at 0.337 mol L⁻¹), 60 min of exposure time plus 2 min of sonication (pulses at 2 s intervals), and 10 min of short-term stability. The relative standard deviation of the method was determined to be 4.04% for 0.4 mg L⁻¹ of Cd(II). The optical sensor was successfully applied to the determination of Cd(II) in natural-water and art-paint samples.

Metal Bioaccumulation and Oxidative Stress in Ulva laetevirens in the Venice Lagoon: Early Warning Biomarker for Metal Bioaccumulation

Transitional water systems (TWSs) may be threatened by various metals originating from increased agricultural, industrial activities, or urban effluents. Macroalgae are one of the biological quality elements used to monitor and assess the health status of TWS due to their structural and functional key role in marine ecosystems. Here, metal accumulation from the macroalgae Ulva laetevirens Areschoug (1854) and oxidative stress by lipid peroxidation (LPO) biomarker were investigated during four sampling seasons from three sampling sites (SMM: Santa Maria del Mare; PM: Porto Marghera; SG: San Giuliano) of Venice Lagoon, affected by different anthropogenic stressors. The metal pollution index (MPI) scores for U. laetevirens increased in the order SMM < PM < SG (sea inlet < industrial area < Osellino River estuary), with average values per site of 2.99, 4.37, and 6.33, respectively. The level of LPO was statistically correlated with the concentration of toxic metal(loid)s (As, Pb, Hg) measured in macroalgae, and seasonality affected both levels of LPO and metal bioaccumulation, with peak values during spring and summer. These findings highlighted the efficiency and usefulness of the oxidative stress test (LPO) on the common macroalga U. laetevirens as an early warning signal for health assessment in aquatic ecosystems.

Determination of Median Lethal Concentration (LC50) and Nitrite Accumulation in the Blood and Tissue of Blood Cockle (Tegillarca granosa, Linnaeus 1758)

This study aimed to determine the nitrite toxicity of blood cockle Tegillarca granosa, with the objectives being to identify the median lethal concentration (LC50) and the accumulation level of nitrite in Tegillarca granosa, and to determine the relationship of nitrite accumulation with mortality percentage. The levels of LC50 and accumulation of nitrite were determined after 72 h of exposure to different nitrite concentrations (0, 0.5, 1.0, 1.5, and 2.0 mg/L). Nitrite accumulation was analysed using Method 8153 and a DR2800 spectrophotometer (HACH, Loveland, CO, USA). LC50 was identified at 1.53 mg/L, and nitrite accumulated in the ranges of 0.012 to 0.106 mg/L wet weight and 0.002 to 0.089 mg/L wet weight in the blood and soft tissue samples, respectively. Accumulation concentration in both tissue and blood cells increased proportionally with the exposure concentration, and had a strong positive relationship with the percentage of mortality. Our findings suggest that prolonged exposure of nitrite led to accumulation in the blood and tissues and caused cockle mortality.

Concentrations of Metals in Tissues of Cockle Anadara granosa (Linnaeus, 1758) from East Java Coast, Indonesia, and Potential Risks to Human Health

This study reports the presence of Cd, Pb, Zn, Hg, Cu, and Cr in the cockles (Anadara granosa, Linnaeus, 1758) harvested along the East Java Coast, Indonesia. The concentrations of metals were determined by atomic absorption spectrometer and expressed in mg kg⁻¹ wet weight. The concentrations of metals ranged from 0.11 to 0.82 mg kg⁻¹ for Cd, 0.10 to 0.54 mg kg⁻¹ for Pb, 10.22 to 19.04 mg kg⁻¹ for Zn, 0.02 to 1.47 mg kg⁻¹ for Hg, 1.79 to 4.76 mg kg⁻¹ for Cu, and 1.64 to 3.79 mg kg⁻¹ for Cr. The metal concentrations in the whole tissues of cockles were in the order Zn>Cu>Cr>Hg>Cd>Pb. The Cd and Pb levels in cockles were found to be higher than the permissible limit for human consumption according to EC and FAO; the levels of Hg exceeded the EC, Hong Kong, Australia, and Indonesia standards; and the levels of Cr exceeded the Hong Kong standard. The estimated weekly intake (EWI) of cockles indicates that the concentrations of Cd and Hg in the cockle tissues from Gresik were higher than the provisional tolerable weekly intake (PTWI); meanwhile, the concentrations of Cr of cockles from all locations were higher than and close to the PTWI. The THQ values for Cd at Gresik, for Hg at Gresik, Surabaya, and Pasuruan, and for Cr at all locations were higher than one indicating that these metals pose potential noncarcinogenic effects to consumers. Reducing the consumption of cockles should be done in order to minimize the adverse effects of metals especially Cd, Hg, and Cr to human health.

Monitoring metal pollution on coastal lagoons using Cerastoderma edule-a report from a moderately impacted system in Western Portugal (Óbidos Lagoon)

The main goal of this monitoring program was to evaluate the contamination in the intertidal environment of Óbidos Lagoon by the metals Cd, Pb, and Ni on water, sediments, and on biological samples, using the bivalve Cerastoderma edule (common name: cockle) as a biomonitor. Since C. edule is an edible mollusc, the risk of their consumption by humans from this lagoon was also evaluated. The study was performed in a restricted area of the lagoon-the ML station-where human activities, such as shellfish harvesting, intersect with the natural processes occurring in this system. The results obtained revealed that the water samples were polluted with Cd and Pb with concentrations (0.00025 mg l^-1 and 0.0072 mg l^-1) above the maximum legislated on the Directive 2008/105/EC, while for Ni, this occurred only on one of the seasons sampled (summer 2010: 0.029 mg l^-1). The sediments were not contaminated with Cd and Ni, and the contamination detected for the metal Pb, allowed the classification of this station as an unpolluted site ([Pbmin] = 7.477 mg.kg^-1 and [Pbmax] = 19.875 mg.kg^-1). On biological samples, comparing the results of metal contaminations with the values of the maximum levels fixed by European Commission Regulation (EC) No 1881/2006 and USFDA, all the results were below the legal value. Therefore, during the period of study, the consumption of this bivalve by humans was safe. Also, BAF and CF calculations suggest that C. edule can be used as a biomonitor to determine the source of the contaminations. This study supported the use of C. edule as a biomonitor to assess the contamination by the metals Pb and Ni at the Óbidos Lagoon and allowed to predict the potential transfer of metals to higher trophic levels with potential impacts on the natural and human communities.

Interactive effects of contamination and trematode infection in cockles biochemical performance

Anthropogenic activities, especially those involving substances that pollute the environment can interfere with bivalve populations, as well as parasitism, a fundamental ecological interaction often neglected. In marine environments, organisms are concomitantly exposed to pollutants and parasites, a combination with synergistic, antagonistic or additive effects representing a potential threat to aquatic communities sustainability. In the present study, Cerastoderma edule (the edible cockle)-Himasthla elongata (trematode) was used as host-parasite model. Cockles are worldwide recognized as good sentinel and bioindicator species and can be infected by several trematodes, the most abundant macroparasites in coastal waters. Tested hypotheses were: 1) cockles exposed to increasing parasite pressure will present greater stress response; 2) cockles exposure to arsenic (single concentration test: 5.2 μg L^-1) will change parasite infection success and cockles stress response to infection. Arsenic was used for being one of the most common pollutants in the world and stress response assessed using biochemical markers of glycogen content, metabolism, antioxidant activity and cellular damage. Results showed that intensity of parasite pressure was positively correlated to biochemical response, mainly represented by higher metabolic requirements. Contamination did not affect parasite infection success. Compared to arsenic, trematode infection alone exerted a stronger impact: higher glycogen storage, metabolism and cellular damage and antioxidant activity inhibition. In interaction, parasitism and arsenic reduced hosts metabolism and cellular damage. Therefore, to a certain extent and in a contamination scenario, cockles may benefit from trematode infection, working as a protection for the pollutant accumulation in the organisms, reducing overall ROS production, which can consequently led to less toxic effects. These findings highlighted the deleterious effects of trematode infection in their hosts and showed the importance of including parasitology in ecotoxicological studies.

Metals and As content in sediments and Manila clam Ruditapes philippinarum in the Tagus estuary (Portugal): Impacts and risk for human consumption

The Manila clam is emerging as a relevant species for the Portuguese market. The present work was conducted in the Tagus estuary to evaluate 1) the metals and As content in the sediments of the Tagus estuary, especially on those areas subjected to Manila clam harvesting 2) the metals and As content in clams, and the risk associated with their consumption 3) the physiological and biochemical responses of the clam to metals and As contamination, and its possible role as a pollution bioindicator in the estuarine environment. The most contaminated sediments were identified nearby industrial areas, nevertheless clams collected in low contaminated areas showed high metals and As concentrations. The condition index, glycogen content, membrane oxidative damage, biotransformation enzymes and metallothioneins showed consistent responses to metals and As content in clams. Results emphasize the need for the development of a management plan for the species exploitation in the Tagus estuary.

Seafood consumption among Chinese coastal residents and health risk assessment of heavy metals in seafood

The aims of the present study were to obtain the seafood dietary patterns of coastal residents, to determine the concentrations of heavy metals, and to evaluate the possible health risks caused by seafood intake. The daily food intakes of 24 types of seafood were collected from 738 participants from Xiamen, a southern Chinese coastal city, using food frequency questionnaire (FFQ) and dietary history method. One hundred and fifty-six samples of 14 types of highest intake seafood were collected from local markets for lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg), and arsenic (As) determination. Health risks via seafood consumption were evaluated by calculating the target hazard quotient (THQ) and the total hazard index (HI) for carcinogenic and non-carcinogenic effects recommended by the US Environmental Protection Agency. The results showed that the seafood daily intake of Xiamen residents was 61.5 (2.14, 115) g/day. The concentrations of Pb, Cd, Cr, Hg, and As in seafood were ND-0.45 mg/kg, ND-0.19 mg/kg, ND-0.80 mg/kg, ND-0.70 mg/kg, and 0.32-16.9 mg/kg, respectively. Concentrations of Cd and As in some samples were higher than national limitation standards. Consumption of 14 common types of seafood would not pose non-carcinogenic risk. However, some types, such as sparuslatus, oyster, and porphyra tenera, would form a carcinogenic risk. Regardless of a carcinogenic or non-carcinogenic risk, As posed the highest risk on humans. The observed HI value for non-carcinogenic effect of all metals in all seafood reached 0.69-2.20, and the metal orders of risk can be listed as As > Hg > Cr > Cd > Pb, reiterating the risk of As is a matter of concern in seafood from Xiamen markets.

Health risk assessments of heavy metal exposure via consumption of marine mussels collected from anthropogenic sites

A total of 40 marine mussel Perna viridis populations collected (2002-2009) from 20 geographical sites located in two busy shipping lanes namely the Straits of Malacca (10 sites; 16 populations) and the Straits of Johore (8 sites; 21 populations) and three populations (2 sites) on the east coast of Peninsular Malaysia, was determined for Cd, Cu, Fe, Ni, Pb and Zn concentrations. In comparison with the maximum permissible limits (MPLs) set by existing food safety guidelines, all metal concentrations found in all the mussel populations were lower than the prescribed MPLs. In terms of the provisional tolerable weekly intake prescribed by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) and oral reference doses (ORDs) by the USEPA, all the studied metals (except for Pb) were unlikely to become the limiting factors or unlikely to pose a risk for the consumption of the mussel populations. The estimated daily intake (EDI) for average level mussel (ALM) and high level mussel (HLM) consumers of mussels was found to be lower than the ORD guidelines for Cd, Cu, Fe, Ni and Zn. Furthermore, the target hazard quotient (THQ) was found to be less than 1 for ALM consumers but higher than 1 for HLM consumers in some sites. Therefore, there were no potential human health risks to the ALM consumers of the mussels. However, for Pb THQ values, the Pb levels in some mussel populations could create a health risk problem. Present results indicate that the consumption amounts of mussels should be limited for minimizing potential health risks of heavy metals to the HLM consumers.

Bioaccumulation patterns, element partitioning and biochemical performance of Venerupis corrugata from a low contaminated system

The current study reports metals and arsenic (As) concentrations present in sediments and in the native clam Venerupis corrugata, collected in the Ria de Aveiro, one of the most important aquatic systems of the Portuguese coast with high biodiversity and socio-economic value. Because of its ecological importance in its habitat, and being one of the most exploited bivalve mollusks in Portugal, several biochemical biomarkers were evaluated in order to illustrate the species status when under environmental conditions. The concentration of metals and As in the sediments showed an increase of contamination among areas (areas A-E). The results proved higher bioaccumulation in organisms from the area less contaminated (area A, BAF > 1). The concentration of metals and As was predominant (63.4%) in the insoluble fraction of clams. The biochemical evaluation evidenced an increase of oxidative stress in organisms from the most (D and E) and the less (area A) contaminated areas, demonstrated by higher LPO levels, CAT, and GSHt activities at these areas and the increase of methalotionines (MTs) along the concentration gradient. This suggests a preventive mechanism in order to protect cells against pollutants (metals and As).

Ruditapes philippinarum and Ruditapes decussatus under Hg environmental contamination

The native species Ruditapes decussatus and the invasive species Ruditapes philippinarum have an important ecological role and socio-economic value, from the Atlantic and Mediterranean to the Indo-Pacific region. In the aquatic environment, they are subjected to the presence of different contaminants, such as mercury (Hg) and its methylated form, methylmercury (MeHg). However, few studies have assessed the impacts of Hg on bivalves under environmental conditions, and little is known on bivalve oxidative stress patterns due to Hg contamination. Therefore, this study aims to assess the Hg contamination in sediments as well as the concentration of Hg and MeHg in R. decussatus and R. philippinarum, and to identify the detoxification strategies of both species living in sympatry, in an aquatic system with historical Hg contamination. The risk to human health due to the consumption of clams was also evaluated. The results obtained demonstrated that total Hg concentration found in sediments from the most contaminated area was higher than the maximum levels established by Sediment Quality Guidelines. This study further revealed that the total Hg and MeHg accumulation in both species was strongly correlated with the total Hg contamination of the sediments. Nonetheless, the THg concentration in both species was lower than maximum permissible limits (MPLs) of THg defined by international organizations. R. decussatus and R. philippinarum showed an increase in lipid peroxidation levels along with the increase of THg accumulation by clams. Nevertheless, for both species, no clear trend was obtained regarding the activity of antioxidant (superoxide dismutase, catalase) and biotransformation (glutathione S-transferase) enzymes and metallothioneins with the increase of THg in clams. Overall, the present work demonstrated that both species can be used as sentinel species of contamination and that the consumption of these clams does not constitute a risk for human health.

Biochemical performance of native and introduced clam species living in sympatry: The role of elements accumulation and partitioning

The present study reports metal and arsenic contamination in sediments, as well as element accumulation and partitioning in native (Ruditapes decussatus and Venerupis corrugata) and introduced (Ruditapes philippinarum) clam species living in sympatry at the Óbidos lagoon (Portugal). The biochemical performance and the human health risks derived from the consumption of these species are also discussed. The results obtained showed that R. decussatus was the most abundant species in all the sampling sites, revealing that the introduced clam has not yet supplanted the native species. The concentration of elements was higher in areas with higher Total Organic Matter (TOM) and fines content, being Chromium (Cr), Copper (Cu) and Lead (Pb) the most abundant metals. Clams from these areas showed the highest concentration of elements but the lowest bioaccumulation levels. Furthermore, except for As, higher concentration of elements was found in clams insoluble fraction, the less toxic fraction to the organisms. Due to the low contamination levels and because elements, except As, were mainly allocated to the insoluble fraction, clams presented similar biochemical parameters among distinct areas, with no significant oxidative stress induced. Furthermore, clams from the Óbidos lagoon represent a low health risk to human consumption since, except for As, their contamination levels were below the maximum permissible limits defined by international organizations.

Venerupis decussata under environmentally relevant lead concentrations: Bioconcentration, tolerance, and biochemical alterations

The edible clam Venerupis decussata is widely distributed in European aquatic systems, some of which are under strong anthropogenic pressure, which can contribute to trophic transfer of xenobiotics to humans. Accordingly, the present study focused on the tolerance, bioconcentration, and biochemical responses of V. decussata after exposure to ecologically relevant concentrations of lead. Health risks to humans after consumption of clams was also explored. An acute toxicity assay (96 h) was conducted with wild clams, using Pb exposure concentrations ranging from 0 mg L(-1) to 1.80 mg L(-1). Lethality, bioconcentration factor (BCF), intracellular partitioning, and a relevant set of biomarkers were used as endpoints. Clams, interstitial water, water column, and sediment samples were collected to analyze Pb concentration. The Pb concentration in wild clams was below international consumption guidelines. Under laboratory conditions, clams revealed high sensitivity to Pb (median lethal concentration of 0.65 mg L(-1)), with a high bioconcentration ability (bioconcentration factor > 1) during exposure. The intracellular partitioning data showed that most of the Pb had accumulated in the insoluble fraction (>80%). Several significant biochemical changes were observed, namely on catalase and glutathione-S-tranferase activities and metalothionein content. Overall, it was demonstrated that the European clam has a reduced tolerance to Pb, compared with other bivalves. However, consumption of clams from the Ria de Aveiro lagoon (Portugal) does not raise public health concerns in terms of Pb.

Trematode communities in cockles (Cerastoderma edule) of the Ria de Aveiro (Portugal): influence of inorganic contamination

This work aims to assess the trematode parasites infecting the edible cockle Cerastoderma edule, collected in the Ria de Aveiro lagoon, one of the most relevant biodiversity hotspots of the Western Iberia, and evaluate the relationship between the observed patterns and environmental descriptors. A total of 11 of the 16 trematode species known to infect C. edule were identified, including Himasthla continua and Psilostomum brevicolle as new occurrences in this lagoon. Parvatrema minutum was the most abundant and dominant species. Species richness and prevalence were high. The relationship between trematode species abundance, intensity and prevalence, and also environmental variables, showed that most parasites preferred muddy sand areas with euhaline conditions in opposition to areas with contamination and/or distant from the lagoon entrance. This study highlighted the good ecological status of the ecosystem and the transitional biogeographic characteristics of the western Portuguese coast where northern and subtropical faunas can coexist.

Determination of toxic elements (mercury, cadmium, lead, tin and arsenic) in fish and shellfish samples. Risk assessment for the consumers

Although fish intake has potential health benefits, the presence of metal contamination in seafood has raised public health concerns. In this study, levels of mercury, cadmium, lead, tin and arsenic have been determined in fresh, canned and frozen fish and shellfish products and compared with the maximum levels currently in force. In a further step, potential human health risks for the consumers were assessed. A total of 485 samples of the 43 most frequently consumed fish and shellfish species in Andalusia (Southern Spain) were analyzed for their toxic elements content. High mercury concentrations were found in some predatory species (blue shark, cat shark, swordfish and tuna), although they were below the regulatory maximum levels. In the case of cadmium, bivalve mollusks such as canned clams and mussels presented higher concentrations than fish, but almost none of the samples analyzed exceeded the maximum levels. Lead concentrations were almost negligible with the exception of frozen common sole, which showed median levels above the legal limit. Tin levels in canned products were far below the maximum regulatory limit, indicating that no significant tin was transferred from the can. Arsenic concentrations were higher in crustaceans such as fresh and frozen shrimps. The risk assessment performed indicated that fish and shellfish products were safe for the average consumer, although a potential risk cannot be dismissed for regular or excessive consumers of particular fish species, such as tuna, swordfish, blue shark and cat shark (for mercury) and common sole (for lead).

Consumption of Ruditapes philippinarum and Ruditapes decussatus: comparison of element accumulation and health risk

Ruditapes philippinarum, a species native from the Indo-Pacific region, was introduced in Europe at the beginning of the 1970s for culture purposes, leading to a massive decrease of the native species Ruditapes decussatus and a high increase of R. philippinarum yields in Europe. Bivalves can accumulate high amounts of metals and thus easily reach concentrations that are toxic not only to themselves but also to consumers. Since differences in the accumulation of pollutants may exist between bivalve species, different health risks may be overcome. For this reason, the level of metals in seafood raises public health concerns, and international organisations like European Food Safety Authority, United States Food and Drug Administration, and Food Standards Australia and New Zealand (FSANZ) set maximum levels (MLs), above which edible seafood cannot be marketed. In order to evaluate the risk associated with the consumption of R. philippinarum and R. decussatus, both clam species were collected in the same site in Ria de Aveiro and the concentration of eight elements determined in organisms before and after a 48-h depuration period. Results evidence that even at low contaminated areas, the MLs for some elements can easily be achieved. The concentrations of As were above the reference values for FSANZ, and the provisional tolerable weekly intake (PTWI) is exceeded for As when more than 0.5 kg of R. decussatus and 0.9 kg of R. philippinarum clam flesh is consumed, in 1 week, by an adult (70 kg). When comparing with other systems worldwide, consumers of depurated clams from this coastal system have a similar or lower risk of exceeding the PTWI for Cd, As, Pb, and Hg. The recently introduced clam, R. philippinarum, accumulates lower amounts of the most health-threatening elements (less than 71 % of Cd, 40 % of As, and 20 % of Hg) than the native R. decussatus, except for Pb. R. philippinarum also reduces more the element burden when subjected to depuration than R. decussatus. Moreover, R. philippinarum allocates a lower proportion of the accumulated elements in the soluble fraction, where they are readily available. Thus, it is safer to consume R. philippinarum than R. decussatus, except when clams come from areas heavily polluted by Pb.

Heavy metal concentrations in edible barnacles exposed to natural contamination

The giant barnacle Megabalanus azoricus is a popular seafood in the Azores. It is mainly caught in coastal environments and sold for domestic human consumption. This species is a filter feeder and can be used as a biomonitor of trace metal bioavailabilities. To investigate consumption safety, the concentrations of 10 trace metals - As, Cd, Cr, Cu, Mn, Pb, Rb, Se, Sr and Zn - were evaluated in 3 body tissues of M. azoricus from 3 sites on 2 islands. There were no significant differences between the metal loads of the barnacles from the different sites. However, the concentrations of the total trace metal loads revealed significant differences among the tissues (cirrus, muscles and ovaries). The concentrations of some metals in the body were not within the safety levels for consumers, based on the allowable standard levels for crustaceans issued by the European Union and of legislations in several countries. Alarming levels of As and Cd were found. Considering the absence of heavy industry in the region, a non-anthropogenic volcanic source was assumed to be the reason for the observed metal levels. Barnacles, in particular M. azoricus, seem to be useful as bioindicators in this peculiar environment.

Mercury bioaccumulation and decontamination kinetics in the edible cockle Cerastoderma edule

Mercury bioaccumulation and decontamination kinetics in the edible cockle Cerastoderma edule were studied through a mesocosms experiment after a medium-term exposure to the metal. The results revealed that the bivalve presented distinct bioaccumulation kinetics according to the different tissues. While the gills showed a linear accumulation pattern, the digestive gland and the entire organism presented a saturation model, with higher accumulation during the first 7d of exposure and lower during the rest of the time. In addition, the bioaccumulation rate was not proportional to the Hg concentration, since the organisms under lower contamination presented higher bioconcentration factors than the ones under higher contamination. Gills were the tissues with higher mercury accumulation capability. Concerning the decontamination phase, C. edule lost approximately 80% of the mercury after 24h exposure in clean seawater. Nevertheless, never reached the original condition, showing in the final (20 d detox), Hg levels (>0.5 ppm) higher than those allowed by the legislation regulating human food consumption. This represents a matter of concern for Human health.

Physiological responses of the European cockle Cerastoderma edule (Bivalvia: Cardidae) as indicators of coastal lagoon pollution

Physiological responses can be used as effective parameters to identify environmentally stressful conditions. In this study, physiology changes such as oxygen consumption, clearance rate, survival in air, condition index and energy reserves were measured on natural populations of cockles collected from different sites at Ria de Aveiro, Portugal. At those sites, sediment samples were collected for Hg concentration analysis. Cockles were used for the evaluation of both the Hg concentration and physiological response. Mercury was detected in the cockle tissue and in the sediment collected from the sampling points both nearby and distant from the main mercury contamination source. The energy content was negatively correlated with both Hg concentration in cockle tissues and survival in air. Nonetheless, the energy content was positively correlated with the condition index, and there was a positive correlation between the survival in air test and the tissue mercury concentration. A PCA-factor analysis explained 86.8% of the total variance. The principal factor (62.7%) consisted of the air survival, the Hg in soft tissues (positive) and the condition index (negative). The second factor (24.1%) consisted of a negative correlation between the oxygen consumption and the clearance rate. Due to their sensitivity to environmental conditions, the physiological responses of cockles can be used to assess the ecological status of aquatic environments. More effort should be invested in investigating the effects of environmental perturbations on cockle health once they are a good reporter organism.

Looking for suitable biomarkers in benthic macroinvertebrates inhabiting coastal areas with low metal contamination: comparison between the bivalve Cerastoderma edule and the Polychaete Diopatra neapolitana

Metals accumulated in marine sediments are often a threat to benthic communities. With the recognized importance and wide use of stress biochemical responses as indicators of metal contamination it becomes essential to compare these markers between different species and verify their ubiquity and accuracy. Using wild Diopatra neapolitana and Cerastoderma edule, collected at several areas differing in metal contamination, this study aimed to assess the use of these two macrobenthic species as sentinel organisms and to determine the applicability of currently used biomarkers in benthic species exposed to a range of low metal and As concentrations. Total metal accumulation and intracellular partitioning was analyzed and metal-induced alterations were assessed through the analysis of several biochemical parameters in both organisms, including stress-induced reactive oxygen species (ROS), lipid peroxidation and protein content, the activity of antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and of glutathione S-transferase (GST). Metal chelation by Metallothioneins (MTs) was also determined. Results revealed that D. neapolitana accumulated higher levels of metals when compared to C. edule, independently of the sediment concentration. Results also showed strong species-specific responses to metals and differences in the ability to sequester metals. Overall, C. edule showed to be more efficient metal chelator and precipitatior than D. neapolitana, which was less tolerant and presented oxidative stress. MTs proved to be a good predictor of metal accumulation in both species, even under low metal exposures. On the other hand, lipid peroxidation was a good indicator of oxidative damage, only observed in D. neapolitana, which was a result of higher metal retention in the soluble fraction.