Bivalve Samples Research Articles

Strontium isotope dating of bivalve faunas from the Upper Miocene Cacela Formation, eastern Algarve, Portugal: Evidence from Messinian bivalve fauna

The study is focused on the determination of the geological age of bivalve fauna recovered from four fossiliferous sequences in the Cacela Formation of Algarve, southern Portugal, by means of the strontium isotope stratigraphy. Forty two analyses of bivalve samples from Barroquinha, Cabanas, the Cacela River and Lacem were performed. The estimated age based on the 87Sr/86Sr ratios in bivalve shell samples from the Cacela River (a reference section for the Cacela Formation) is 7.6 ± 0.4 Ma and is consistent with a late Tortonian age suggested by micropalaeontological data (calcareous nannofossils and planktonic foraminifers). Moreover, strontium isotopic data record that the oldest age of the bivalves of the Cacela Formation (Lacem site) is at least 8.9 ± 0.4 Ma whilst the age of about 7.0 ± 0.5 Ma can be inferred for bivalves from Barroquinha. An intriguing new datum comes, however, from the bivalve strontium isotopic data of the Cabanas section which records the estimated age of about 6.7 ± 0.4 Ma and, therefore, an early Messinian age. This is the first report of the early Messinian marine bivalve fauna in Portugal. Sixty one bivalve species have been recovered in the Messinian of Cabanas. Four of them: Pseudopythina macandrewi (P. Fischer), Coripia corbis (Philippi), Glossus (Glossus) humanus (Linnaeus) and Cyathodonta dollfusi (Cossmann et Peyrot) have previously not been reported from the Miocene of southern Portugal.

Optimization of matrix solid-phase dispersion conditions for UV filters determination in biota samples

A low solvent consumption method for the determination of eight ultraviolet (UV) filters, displaying low to medium polarities, in freeze-dried samples of marine bivalves and fish is proposed. Matrix solid-phase dispersion (MSPD) and gas chromatography with mass spectrometry (GC-MS) were used as sample preparation and determination techniques, respectively. This work describes the influence of several parameters (type and amount of dispersant and clean-up sorbents, as well as elution solvent) on the yield and the selectivity of the MSPD extraction. Under optimized conditions, samples (0.5 g) were ground with 2 g of Florisil in a mortar with a pestle and transferred into a polypropylene syringe, which contained 1 g of C18 as clean-up sorbent. Analytes were eluted with 5 mL of acetonitrile. This extract was concentrated to dryness, re-constituted with 1 mL of ethyl acetate and injected in the GC-MS system without any further clean-up. The global average recoveries, measured for three different biota samples, spiked at three different levels (between 50 and 1000 ng g−1), ranged from 80% to 101% with associated standard deviations below 10%. The inter-day precision of the method varied from 4% to 15% and the achieved LOQs (defined for a signal to noise ratio of 10) ranged from 4 to 28 ng g−1, referred to the freeze-dried matrix. Octocrylene (OCR) was found in some samples of fish and mussels at concentrations between 15 and 20 ng g−1, referred to dry mass.

Comprehensive monitoring of synthetic musk compounds from freshwater to coastal environments in Korea: With consideration of ecological concerns and bioaccumulation

This study investigated the concentration levels of synthetic musk compounds (SMCs), including HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-(g)-2-benzopyran), AHTN (7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene), MK (Musk ketone), and MX (Musk xylene), in freshwater, freshwater and coastal sediments, and coastal bivalves from freshwater to coastal environments. The levels in freshwater close to sewage treatment plants (STPs) showed higher contamination and suggested a medium to high ecological risk, especially posed by MK making more than 65% contribution to the combined risk by the total SMCs. STP effluent discharge points showed higher SMC concentrations in freshwater and coastal sediments. Predominant HHCB contributions regardless of sample types such as abiota and biota were consistent with the greater usage of HHCB than AHTN and MK in Korea. However, the higher contributions of AHTN than those predicted from AHTN consumption in Korea indicate the need for further research on the characteristic properties of individual SMCs, including partitioning, biomagnification, degradation, and metabolism for a realistic risk characterization. With respect to the highest HHCB levels in coastal bivalves reported, we determined the biota-sediment accumulation factor (BSAF) to understand the bioaccumulation of SMCs between coastal sediment and bivalves. The calculated BSAF values suggested that SMCs in bivalves were not biomagnified via the food chain but mostly partitioned from sediment. To our knowledge, this is the first study to measure BSAF values of SMCs, especially HHCB, AHTN, and MK, in coastal bivalve samples.

Interspecific comparison of polycyclic aromatic hydrocarbons and persistent organochlorines bioaccumulation in bivalves from a Mediterranean coastal lagoon

The bioaccumulation of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) was characterized in cockle, oyster and noble pen shell from nine areas in the Mar Menor lagoon with different hydrodynamic and pollutant sources. Biota, sediment and water samples were simultaneously collected in the spring and autumn of 2010. Considering all bivalve samples, PAH concentrations ranged from 8.98 to 370μg·kg−1 d.w., those of PCBs from 0.15 to 42.36μg·kg−1 d.w. and those of DDXs from below detection limit to 240.6μg·kg−1 d.w., where p,p′-DDE was the main fraction. The bioaccumulation of PAHs was similar for cockle, oyster and noble pen shell, being higher close to ports and wastewater effluents. However, DDX and PCB bioaccumulations in oyster and noble pen shell were significantly higher than in cockle in spring (p=0.02). The first organic pollutant bioaccumulation data for noble pen shell were obtained in this study, showing a preferential accumulation of pyrene. The increase of PAH bioaccumulation in autumn, as compared to spring, was low, due to high water temperatures during the summer, which favoured PAH dissipation processes. No significant seasonal variations were detected for OCPs and PCBs, except in some specific areas. The PAH, PCB and OCP levels detected in these bivalves were lower than OSPAR/MED POL environmental assessment criteria, except for p,p′-DDE in bivalves sited close to El Albujón watercourse mouth.

Rapid and simple method for determination of hexabromocyclododecanes and other LC–MS–MS-amenable brominated flame retardants in fish

In this study, a novel analytical approach for simultaneous determination of hexabromocyclododecane isomers (HBCDs), tetrabromobisphenol A (TBBPA), three brominated phenols, and four hydroxylated derivatives of polybrominated diphenyl ethers (OH-PBDEs) was developed and validated for muscle tissue of both lean and fatty fish. The rapid, simple, and high-throughput sample-preparation procedure was based on acetonitrile extraction then purification by dispersive solid-phase extraction (d-SPE) with a combination of C18 and primary-secondary amine (PSA) sorbents. Ultra-high performance liquid chromatography (UHPLC) coupled to tandem mass spectrometry (MS-MS) was used for identification and quantification of the analytes. Method recovery for both matrices ranged from 80 to 115% with relative standard deviations (RSDs) <13% for all analytes. Limits of quantification (LOQs) were in the range 0.1-1 μg kg(-1) wet weight. The validated method was used for analysis of brominated compounds in 32 fish and five bivalve samples collected from different European markets within the monitoring survey organized in the framework of the CONffIDENCE project. Of the 12 targeted analytes, only α-HBCD, 2,4-dibromophenol (2,4-DBP), and 2,4,6-tribromophenol (2,4,6-TBP) were quantified in the samples. α-HBCD was found in six fish samples (herring and mackerel) in the range of 0.8-2.5 μg kg(-1) wet weight. 2,4-DBP and 2,4,6-TBP were found in three blue mussel samples in the range of 19.6-43.5 and 2.3-7.5 μg kg(-1) wet weight, respectively.

Antimicrobial Activities of Two Edible Bivalves M. meretrix and M. casta

The marine invertebrates become one of hot spot for the lead of antimicrobial compounds. Two species of commercially available and edible bivalves (M. meretrix and M. casta) were assayed for antimicrobial activity against 10 bacterial pathogens and 6 fungal pathogens and its biochemical composition. The bivalves were extracted with three different solvent systems respectively methanol, ethanol and acetic acid. All the three extracts of both the species M. meretrix and M. casta showed highest antibacterial activities against S. aureus, E. coli, B. substillus, K. pneumonia, P. fleuroscence and V. cholera. In present investigation the methanolic extract of the two bivalve species of M. meretrix and M. casta was showed inhibition activities against all pathogenic fungal forms. The two bivalve extracts showed high amounts of protein content, which made the variation up to 160-180 microg mg(-1) (wet weight). Both samples had low amount of carbohydrates 4.77-5.77 microg mg(-1) and lipids 0.11-0.17 microg mg(-1), respectively. The results of thin layer chromatography were revealed that presence of pink color spots it clearly indicates the presence of amino acid or peptides in bivalve's samples. Presuming that the antimicrobial compounds were proteins or peptides. In SDS-PAGE on 12% gel, the crude proteins M. meretrix and M. casta showed 5-6 bands ranging from 45-223 kDa. They represent potential pharmacological leads perhaps possessing novel and uncharacterized mechanisms of action that might ultimately benefit the ongoing global search for clinically useful antimicrobial agents.

Mitogenomics does not resolve deep molluscan relationships (yet?)

The origin of molluscs among lophotrochozoan metazoans is unresolved and interclass relationships are contradictory between morphology-based, multi-locus, and recent phylogenomic analyses. Within the “Deep Metazoan Phylogeny” framework, all available molluscan mitochondrial genomes were compiled, covering 6 of 8 classes. Genomes were reannotated, and 13 protein coding genes (PCGs) were analyzed in various taxon settings, under multiple masking and coding regimes. Maximum Likelihood based methods were used for phylogenetic reconstructions. In all cases, molluscs result mixed up with lophotrochozoan outgroups, and most molluscan classes with more than single representatives available are non-monophyletic. We discuss systematic errors such as long branch attraction to cause aberrant, basal positions of fast evolving ingroups such as scaphopods, patellogastropods and, in particular, the gastropod subgroup Heterobranchia. Mitochondrial sequences analyzed either as amino acids or nucleotides may perform well in some (Cephalopoda) but not in other palaeozoic molluscan groups; they are not suitable to reconstruct deep (Cambrian) molluscan evolution.Supposedly “rare” mitochondrial genome level features have long been promoted as phylogenetically informative. In our newly annotated data set, features such as genome size, transcription on one or both strands, and certain coupled pairs of PCGs show a homoplastic, but obviously non-random distribution. Apparently congruent (but not unambiguous) signal for non-trivial subclades, e.g. for a clade composed of pteriomorph and heterodont bivalves, needs confirmation from a more comprehensive bivalve sampling. We found that larger clusters not only of PCGs but also of rRNAs and even tRNAs can bear local phylogenetic signal; adding trnG–trnE to the end of the ancestral cluster trnM–trnC–trnY–trnW–trnQ might be synapomorphic for Mollusca. Mitochondrial gene arrangement and other genome level features explored and reviewed herein thus failed as golden bullets, but are promising as additional characters or evidence supporting deep molluscan clades revealed by other data sets. A representative and dense sampling of molluscan subgroups may contribute to resolve contentious interclass relationships in the future, and is vital for exploring the evolution of especially diverse mitochondrial genomes in molluscs.

Stratigraphy and wiggle-matching-based age-depth model of late Holocene marine sediments in Beppu Bay, southwest Japan

We analyzed the lithology, magnetic susceptibility, bulk density, and X-ray radiographs of 14 sediment cores (1–9m long) from Beppu Bay in the western Seto Inland Sea, Japan, to establish the late Holocene stratigraphy in the deepest part of the bay and to develop an age–depth model for the sediments there. The cores contained 18 thick (major event) high-density layers (16 turbidites and two volcanic ash; >1cm thick), and both lithological observations and density variations in the hemipelagic mud that is dominant in the cores revealed a further 55 thin (minor event) high-density layers (<1cm thick). Analyses of color properties and opal and sand contents of the hemipelagic mud defined nine lithological units. After stratigraphic correlation of the event layers among cores, we projected 14C dates onto a single composite core. Forty-two AMS 14C dates from bivalve mollusk shells were used to construct a wiggle-matching-based age–depth model for the late Holocene sequence and to determine the local reservoir effect (ΔR). The age–depth model showed a sedimentation rate of 0.23–0.30cm/yr for a 7.8m-long composite core and an age of ∼2800calyr BP at the base. Wiggle-matching provided ΔR values of 115–155yr for late Holocene bivalve samples from Beppu Bay, which is consistent with previous estimates reported from coastal areas near the Kuroshio Front. Comparison of wiggle-matching-derived ages of thick turbidites with the ages of historical earthquakes showed differences within ±25yr. Our study demonstrated that wiggle matching with optimal fitting based on either the weighted least-squares or maximum likelihood method can minimize the effect of scatter of age data due to reworking and burrowing of bivalves and thus improve the accuracy of age–depth models.

Evaluation of different culture media for the isolation and growth of the fastidious Vibrio tapetis, the causative agent of brown ring disease

Thirteen culture media were evaluated at two temperatures for the growth and isolation of Vibrio tapetis. The bacterium showed similar growth dynamics at 15°C or 25°C, being faster at 15°C regardless the general media employed. Best growth of V. tapetis was obtained on Agar Seawater (ASWT) (1.7×106cfu/ml), Mannitol Marine Agar (MMA) (2.6×106cfu/ml), and Mannitol Trypticase Soy Agar (MTSA-1) (1.9×106cfu/ml), being slightly lower on Marine Agar (MA) (5.0×105cfu/ml). Growth was poor on TCBS and nule in the other media containing bile salts, indicating their inhibitory effect on the V. tapetis growth. Recovery of V. tapetis from mixed Vibrio populations, differing in acid production from sucrose and mannitol, was only possible using the selective medium MMA at both temperatures. The use of ASWT or MA at 15°C for the routinary growth of V. tapetis, and MMA for isolation of V. tapetis from bivalve samples is recommended.

Simultaneous analysis of organochlorinated pesticides (OCPs) and polychlorinated biphenyls (PCBs) from marine samples using automated pressurized liquid extraction (PLE) and Power Prep™ clean-up

An automated pressurized liquid extraction (PLE) method followed by Power Prep™ clean-up was developed for organochlorinated pesticide (OCP) and polychlorinated biphenyl (PCB) analysis in environmental marine samples of fish, squid, bivalves, shells, octopus and shrimp. OCPs and PCBs were simultaneously determined in a single chromatographic run using gas chromatography–mass spectrometry-negative chemical ionization (GC–MS-NCI). About 5g of each biological marine sample was mixed with anhydrous sodium sulphate and placed in the extraction cell of the PLE system. PLE is controlled by means of a PC using DMS 6000 software. Purification of the extract was accomplished using automated Power Prep™ clean-up with a pre-packed disposable silica column (6g) supplied by Fluid Management Systems (FMS). All OCPs and PCBs were eluted from the silica column using two types of solvent: 80mL of hexane and a 50mL mixture of hexane and dichloromethane (1:1). A wide variety of fish and shellfish were collected from the fish market and analyzed using this method. The total PCB concentrations were 2.53, 0.25, 0.24, 0.24, 0.17 and 1.38ngg−1 (w/w) for fish, squid, bivalves, shells, octopus and shrimp, respectively, and the corresponding total OCP concentrations were 30.47, 2.86, 0.92, 10.72, 5.13 and 18.39ngg−1 (w/w). Lipids were removed using an SX-3 Bio-Beads gel permeation chromatography (GPC) column. Analytical criteria such as recovery, reproducibility and repeatability were evaluated through a range of biological matrices.

Levels of Polybrominated Biphenyl Ethers in Some Selected Fish and Shellfish from Kuwait

Concentrations of polybrominated diphenyl ethers (PBDEs) in Kuwait's fish market have not previously been reported. Fish from four common species, shrimp, and five common shellfish from Kuwait's fish market were analyzed for seven PBDEs. The levels of PBDEs in fish samples ranged from 0.50 to 3.748 ng/g wet weight and in shellfish samples ranged from 1.05 to 5.47 ng/g wet weight. The mean σ5 PBDE concentrations measured in hamoor, shell, zobaidy, sheim, shrimp, suboor, sponge, octopus, squid, and bivalve samples were 1.49, 5.47, 4.10, 0.50, 3.78, 1.53, 2.10, 3.11, 1.05, and 1.41 ng/g wet weight, respectively. The total PBDE concentration in fish and shellfish samples measured in our study were comparable to or higher than those from other countries. The BDE-47, BDE-99, and BDE-100 were the most dominant PBDEs in all the samples tested. The daily intake of PBDE from fish and shellfish reported in this study was lower than that reported from other countries.

Risk probability due to heavy metals in bivalve from Egyptian Mediterranean coast

Abstract An assessment of marine contamination by eight heavy metals (Al, Cd, Co, Cr, Cu, Ni, Pb, and Zn) made along the Egyptian Mediterranean coast. Also, risk probability due to heavy metals contamination in bivalve was investigated. The bivalve samples collected in April 2007 from nine hot spot locations started at El-Mex and ended at Port-Said along Mediterranean coast. The recorded average concentrations of Al, Cd, Co, Cr, Cu, Ni, Pb, and Zn were 137.8 ± 147.4, 0.09 ± 0.04, 2.45 ± 1.29, 8.49 ± 5.19, 3.82 ± 2.21, 10.28 ± 4.09, 0.24 ± 0.15, and 21.87 ± 21.38 μg g−1 dry weight, respectively. In spite of the mollusks species, El-Mex exhibited the highest metal pollution index (MPI), which is expected due to the presence of industrials and agriculture drain near El-Mex location, followed by Port-Said and Abu-Qir stations that suffer from many industrials, marine transportation, fisheries and human activities. Western Harbor and Damietta stations recorded the lowest MPI. Principal component analysis (PCA) and cluster analysis were applied to highlight the relationships between metals. The dendrograms of the cluster analysis confirm the results obtained with PCA. Indeed, depending on the statistical analysis, the studied metals were grouped into two groups, the first group contains Co, Pb, Zn, Cu, Cd and Ni, and the second group includes the remaining two studied metals (Al and Cr). Risk probability study showed that the risk quotients for Cd, Cu, Ni, Pb, and Zn in both the best-case and worst-case scenarios do not cause adverse effect for either low or high consumption groups. Only chromium recorded a risk quotient three times greater than the worst-case scenarios, which may associate health problem for the heavy shellfish consumers groups.

Determination of Cadmium in Bivalve Molluscs by Microwave Digestion with Inductively Coupled Plasma-Mass Spectrometry

A method based on microwave digestion and inductively coupled plasma-mass spectrometry (ICP-MS) has been established for the sensitive determination of cadmium in bivalve molluscs. The application of the internal standards calibration improved the accuracy and precision values of the method. The relative standard deviation (RSD), the standard addition recovery value and the detection limit were determined as 4.25%, 94.74% and 0.005 μg/L, respectively. This method has been verified by the determination of cadmium in certified reference material kelp (GBW08517) and mussel (GBW08571). The method has been applied to determine the contamination concentration level of cadmium in seven kinds of bivalve mollusk samples. The results indicated that, among them, mud clam, scallop and oyster have relative high accumulation ability to cadmium.

Diversity of Somatic Coliphages in Coastal Regions with Different Levels of Anthropogenic Activity in São Paulo State, Brazil

Bacteriophages are the most abundant and genetically diverse viruses on Earth, with complex ecology in both quantitative and qualitative terms. Somatic coliphages (SC) have been reported to be good indicators of fecal pollution in seawater. This study focused on determining the concentration of SC and their diversity by electron microscopy of seawater, plankton, and bivalve samples collected at three coastal regions in São Paulo, Brazil. The SC counts varied from <1 to 3.4 × 10(3) PFU/100 ml in seawater (73 samples tested), from <1 to 4.7 × 10(2) PFU/g in plankton (46 samples tested), and from <1 to 2.2 × 10(1) PFU/g in bivalves (11 samples tested). In seawater samples, a relationship between the thermotolerant coliforms and Escherichia coli and SC was observed at the three regions (P = 0.0001) according to the anthropogenic activities present at each region. However, SC were found in plankton samples from three regions: Baixada Santista (17/20), Canal de São Sebastião (6/14), and Ubatuba (3/12). In seawater samples collected from Baixada Santista, four morphotypes were observed: A1 (4.5%), B1 (50%), C1 (36.4%), and D1 (9.1%). One coliphage, Siphoviridae type T1, had the longest tail: between 939 and 995 nm. In plankton samples, Siphoviridae (65.8%), Podoviridae (15.8%), Microviridae (15.8%), and Myoviridae (2.6%) were found. In bivalves, only the morphotype B1 was observed. These SC were associated with enteric hosts: enterobacteria, E. coli, Proteus, Salmonella, and Yersinia. Baixada Santista is an area containing a high level of fecal pollution compared to those in the Canal de São Sebastião and Ubatuba. This is the first report of coliphage diversity in seawater, plankton, and bivalve samples collected from São Paulo coastal regions. A better characterization of SC diversity in coastal environments will help with the management and evaluation of the microbiological risks for recreation, seafood cultivation, and consumption.

Potentially toxic trace elements accumulating in marine sediment and bivalves in the outfall area of a desalination plant

This study evaluated the environmental impact of seawater desalination effluent discharged into a water body by investigating potentially toxic trace elements in the outfall area of a desalination facility on the southeastern coast of the Penghu Island (Taiwan). Trace element concentrations are analyzed using various samples (sediment, water and bivalves). Copper, zinc and arsenic were detected in sediment samples in the outfall area and decreased progressively as one moved away from this area. A contour plotting technique was applied to assess and visualize trace element pollution point sources (inputs) in the study area. Trace element concentrations measured directly in the desalination plant effluent confirm analytical results. Bivalve samples such as oysters and clams were collected 50 m from the desalination coastal area. Trace element concentrations in bivalves varied randomly. A clear increasing tendency over time (bioaccumulation) was not observed. This study cannot support the use of trace elemen...

Nonylphenol in bivalves and sediments in the northeast coast of China

To understand nonylphenol (NP) contamination in the northeast coastal environment in China, NP was determined in 19 sediment and 20 bivalve samples collected during November 2005. NP was identified in all sediment samples in the range of 8.8 to 1.0 × 10 3 ng/g dw (dry weight), with an average of 0.12 × 10 c ng/g dw. Most of the bivalve samples (oysters and mussels) contained detectable amounts of NP that ranged from ND (not detected) to 7.6 × 10 c ng/g dw, with an average value of 0.79 × 10 c ng/g dw. These results indicated that NP is ubiquitous in sediments and bivalves from the northeast coast of China, and are even present in bivalves sold as seafood. Serious contamination with NP was recorded off the coast of Bohai Strait and in semi-enclosed coastal environment such as Jiaozhou Bay and Liaodong Bay. Possible environmental and human health implications were understood in this study.

한국 연안 이매패류에 잔류하는 PBDEs 및 OCs에 관한 연구

Bivalve samples from 30 locations Korean coastal waters were analyzed to characterize the contamination with and distribution of polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). The congeners of PBDE in 30 bivalve samples were analyzed by high resolution gas chromatography with a high resolution mass detector. The levels of PBDEs in bivalve samples ranged from 0.092 to 13.5 ng/g wet weight. These values for PBDEs concentrations in bivalves from Korea were higher than or comparable to available values for bivalves from other countries. In the congener profiles, BDE-47 (mean contribution=42.2%) was predominant, followed by BDE-99 (23.1%), BDE-100 (11.9%) and BDE-154 (3.5%). Among the OCs analyzed, PCBs and DDTs levels were highest, followed by HCHs, CHLs and HCB. The wet weight based PCBs and DDTs ranged from 0.28 ng/g to 19.4 ng/g, and from 0.19 ng/g to 4.86 ng/g, respectively. The PCBs and DDT slevels in bivalves along the entire Korean coast were lower than those of the USA, and below the Food and Drug Administration (USA. FDA) limits for fish and shell fish. However, the human health criteria and wild life criteria of the USA. Environmental Protection Agency (USA. EPA) were exceeded for DDE and HCHs at most of the sampling points.

Temporal variation ofMeiogymnophallus minutusinfections in the first and second intermediate host

In order to study seasonal patterns of Meiogymnophallus minutus infections in its intermediate hosts, bivalve samples were collected monthly between April 2008 and March 2009 from a high intertidal flat at Courtmacsherry Bay, Ireland. Infection rates in the first intermediate host Scrobicularia plana did not fluctuate significantly with season. Completely developed M. minutus cercariae appeared in daughter sporocysts from June and prevailed from July to October, indicating that transmission of M. minutus from its first to its second intermediate host is confined to this period of the year. All analysed individuals of the second intermediate host Cerastoderma edule were found to be infected with metacercariae. Infection levels significantly increased in September, suggesting recent cercarial invasions. Throughout the year, the majority of metacercariae were hyperinfected by the pathogenic microsporidian Unikaryon legeri. Spreading of hyperinfections was confined to spring and summer. Newly settled metacercariae were not affected by hyperparasitism and presumably retained their infectivity for half a year. Our findings suggest that the spreading of hyperinfections is correlated with higher water temperatures and that the entire metacercarial population has to rebuild every year as a consequence of hyperparasite-induced mortality.

Polychlorinated biphenyls, organochlorine pesticides and polycyclic aromatic hydrocarbons in a one-off global survey of bivalves

During the Danish Galathea 3 expedition, bivalve samples were collected at the Faroe Islands, Greenland, Ghana, South Africa, Australia, Solomon Islands, New Zealand, Chile, US Virgin Islands, Boston, Newfoundland and Shetland Islands and analysed for organochlorines and PAHs. Concentration differences of up to three orders of magnitude were observed, with the highest concentrations at Boston harbour (SPCB 338 ng g(-1) dw, ΣSPAH 5966 ng g(-1) dw) and the Sydney estuary (ΣSPCB 282 ng g(-1) dw, SPAH 1453 ng g(-1) dw). Local impacts were also found for the Greenland capital Nuuk in terms of PCB and PAH levels, while other Greenland samples came closest to representing PAH background levels. Several locations had undetectable organochlorine levels, including Hobart and Chile, which had the lowest SPAH concentrations (<200 ng g(-1) dw). It was possible to group the stations according to their pyrogenic/petrogenic influence using Principal Component Analyses, and indications of petroleum sources were found at Nuuk.

Risk assessment in shellfish-borne outbreaks of hepatitis A.

In the present work, we aimed at determining the relationship between the hepatitis A virus (HAV) numbers in imported frozen coquina clams involved in two hepatitis outbreaks, as well as the risk for human health. Due to HAV unculturability, a standardized TaqMan real-time reverse transcription-PCR controlling the virus/nucleic acid extraction and enzyme efficiencies was employed to figure the exposure dose for clams responsible for hepatitis cases. HAV numbers were then employed to figure the risk of infection based on a dose-response model for echovirus 12. The estimated risk of infection after consumption of lightly cooked clams matched actual attack rates. Our data show that prospective monitoring of bivalve samples may fail to prevent the occurrence of outbreaks, since HAV was detected in 44% of samples directly associated with cases but was undetectable in samples that were randomly collected from the importers and belonged to the same batches. A correlation was nevertheless observed between the prevalence of hepatitis A cases in the harvesting areas and positive HAV isolation in clams, which points to the need to identify and prevent hazards rather than relying on random sampling of finished products to ensure safety. However, when evidence shows that a critical limit of viral contamination has been exceeded in the potential sources of contamination discharging into the shellfish-growing beds, quantitative virological analysis addressing quality assurance and quality control requirements should be performed with the bivalves. This work provides the first evidence of accurate HAV levels in shellfish involved in outbreaks that could be of use for risk assessment purposes.