Mussel Tissue Research Articles

Assessing the Effect of Contaminated and Restored Marine Sediments in Different Experimental Mesocosms Using an Integrated Approach and Mytilus galloprovincialis as a Model.

The research presented here was conducted to ascertain the effectiveness of recovery technologies in remediating a compromised marine environment. The multidisciplinary approach aims to integrate traditional chemical-physical analysis and to assess the biological parameters of Mytilus galloprovincialis within different experimental mesocosms (W, G, and B). In particular, this system was designed to reproduce sediment resuspension in a marine environment, which is thought to be one cause of contaminant release. The study combined morphological and ultrastructural observations with DNA damage assessment and mRNA expression of those genes involved in cellular stress responses. The tissues of mussels maintained in the polluted mesocosm showed a higher accumulation of Pb and Hg than in those maintained in restored mesocosm. This observation correlates well with mRNA expression of MT10 and data on DNA damage. The outcome of the biological evaluation consolidates the chemical characterization and supports the concept that the remediation method should be evaluated at an early stage, both to analytically determine the reduction of toxic components and to assess its ultimate impact on the biological system.

Multianalyte voltammetric determination of traffic-linked metals in marine organisms employed as pollution bio-monitors

ABSTRACT A new procedure is proposed for the voltammetric determination of ultra-trace cadmium(II), copper(II), lead(II), platinum(II), palladium(II), rhodium(III) and zinc(II) by a single run of square wave adsorptive catalytic stripping voltammetry. The voltammetric cell was based on a typical three-electrodes set-up: working electrode (stationary hanging mercury drop), reference electrode (Ag|AgCl|KClsat) and auxiliary electrode (platinum). The supporting electrolyte contained the formazone complex together with dimethylglyoxime and the disodium salt of ethylenediaminetetraacetic acid. Validation of the analytical procedure was obtained by the analysis of standard reference materials (Mussel Tissue BCR-CRM 278, Oyster Tissue NIST-SRM 1566a). Comparison with spectroscopic measurements was performed. Good accuracy was achieved. The analytical procedure was finally applied to mussels and clams sampled on the mouth of Po river, employed as bio-monitors.

Sub-lethal toxicities of zinc pyrithione, copper pyrithione alone and in combination to the indicator mussel species Unio crassus Philipsson, 1788 (Bivalvia, Unionidae)

ABSTRACTZinc pyrithione (ZnPT) and copper pyrithione (CuPT) are widely used antifouling booster biocides in the shipping industry as a replacement for the banned tributyltin (TBT). Sub-lethal effects of zinc pyrithione (ZnPT; 10 μg L−1), copper pyrithione (CuPT; 10 μg L−1) and combined copper–zinc pyrithione (CZPT; 5 + 5 and 10 + 10 μg. L−1) to freshwater indicator mussel Unio crassus (5.49 ± 0.85 cm in size) were determined by investigation of the total hemocyte counts, biochemical analysis mussel tissues and histopathological observations after 48-h and 7-d exposures. Mean total hemocyte counts differed significantly among all groups, for both exposure durations. In the 7 d, lipid peroxidation levels (malondialdehyde, MDA nmol g−1 wet tissue) and reduced glutathione levels (GSH μmol g−1 wet tissue) were lower than 48 h. However, there were no significant differences among groups. Total protein levels (mg mL−1) were approximately in the same range and differed only among 7-d exposure groups. The gill tissues showed hemocytic infiltration and lipofuscin like structures, while digestive gland showed loss of digestive tubules in the treatments of pyrithione compounds. Histopathological damages were most severe in the combined exposure groups. In conclusion, ZnPT, CuPT and combined CZPT5/10 are highly toxic on a freshwater indicator mussel species U. crassus.

Ecological Stoichiometery and Consumer-Driven Nutrient Recycling by Elliptio complanata (Lightfoot) in a Northeastern Coastal Zone Pond

Freshwater mussels recycle nutrients within their environment, and the extent of their influence depends on ambient nutrient concentrations and time of year. This study investigated the stoichiometry of consumer-driven nutrient recycling (C, N, and P) of the numerically dominant indigenous freshwater mussel Elliptio complanata (Eastern Elliptio) in a New England pond, which we accomplished by evaluating the stoichiometry of seston, mussel tissues, excretion, and biodeposition. Based on our results, we identified 4 major findings. First, we found seston CNP was not variable across seasons as expected, with only 4 of 10 pairwise interactions being statistically significant, and did not necessarily match the Redfield ratio as expected with higher C:N and lower C:P and N:P observations. Second, we found our tissue CNP to be below the expected 106:16:1 Redfield ratio and that the mussels did not adhere to strict stoichiometric homeostasis throughout different sizes/ages, as shown with 5 of 12 regressions being statistically significant. Third, we found freshwater mussel excretion to be similar to that found in other studies and that excretion rates and ratios were influenced by size and shifted with changes in season—possibly related to seston composition as well as environmental conditions such as temperature, based on 7 of 10 statistical analyzes being significant. Finally, we found freshwater mussel biodeposition to be variable across time for nutrient rates and ratios as we expected.

Accumulation and esterification of diarrhetic shellfish toxins from the aqueous phase in laboratory-exposed mussels

In recent years, marine bivalves cultured in the natural environment have been confirmed to accumulate diarrhetic shellfish toxins (DSTs) from the aqueous phase. To investigate the effects of varying seston concentrations on DST accumulation, mussels (Mytilus galloprovincialis) were exposed to comparable concentrations of okadaic acid (OA) and dinophysistoxin-1 (DTX1) in 0.45-μm filtered seawater spiked with varying concentrations of ambient suspended particles at 0, 10, 30, 60, 90, and 120 mg L−1, for 96 h. Effects of seston additions on the mussels’ feeding on nontoxic microalgae, Isochrysis galbana, the stability of dissolved toxins and the anatomical compartmentalization of toxins were also assessed. Results showed that mussels more readily accumulated OA than DTX1 from the aqueous phase. Three potential mechanisms of the effects of seston on toxin accumulation were identified. First, seston at low concentrations (10 mg L−1) adsorbed toxins and thus promoted toxin accumulation. Second, seston enhanced the degradation of aqueous OA and DTX1, and possibly reduced the adsorption by digestive gland (DG) cells through simple diffusion due to competitive adsorption. Third, the clearance rate of mussels was significantly reduced at high seston concentrations (120 mg L−1). The esterification of DSTs was maximized in DG tissue, although a high percentage (52%) of DSTs was distributed in non-visceral tissues of mussels exposed to aqueous toxins. This study suggests that the risk of benthic DST-producing microalgae to marine cultured shellfish should be taken into consideration, even in the absence of a bloom of toxic microalgae in the water column.

Plastics and biodegradable plastics: ecotoxicity comparison between polyvinylchloride and Mater-Bi® micro-debris in a freshwater biological model

The improper release of plastic items and wastes is nowadays one of the main environmental and social problems, whose solution or mitigation represents a great challenge worldwide. In this context, the growing use of the so-called biodegradable plastics could represent a possible solution in the short to medium term. The few information known about the ecological impact of these materials on freshwater organisms, especially the ones relative to the micro-debris derived from their aging, prompted us to study the comparison of the sub-lethal effects eventually caused by plastic and biodegradable plastic micro-debris on the mussel Dreissena polymorpha, which represents an excellent biological model for the freshwater ecosystems. We selected two powders of polyvinylchloride (PVC) and Mater-Bi® administered at 1 mg/L to D. polymorpha specimens in semi-static conditions for 14 days. The presence of micro-debris was evaluated on mussel tissues and pseudo-faeces using advanced microscopy techniques. The sub-lethal effects were investigated on exposed mussels at 6 and 14 days using a suite of biomarkers of cellular stress, oxidative damage, and genotoxicity. Lastly, we compared the ecotoxicity of these two materials integrating each endpoint in the Biomarker Response Index. Microscopy observations highlighted the surprising absence of micro-debris in the gut lumen and tissues of exposed mussels, but the presence of both PVC and Mater-Bi® micro-debris in the pseudo-faeces, suggesting a possible efficient elimination mechanism adopted by mussels to avoid the micro-debris gulping. Consequently, we did not observe significant sub-lethal effects, except for the glutathione-S-transferase activity modulation after 6 days of exposure.

Intertidal mussels do not stop metal bioaccumulation even when out of water: Cadmium toxicokinetics in Xenostrobus atratus under influences of simulated tidal exposure

Intertidal bivalves are periodically exposed in air. It is tempting to speculate that the organisms would temporarily escape from contaminants when they are out of water and thus have lower risks. In this study, we tested this speculation by investigating cadmium (Cd) toxicokinetics in an intertidal mussel, Xenostrobus atratus, under the effects of tidal exposure using simulated tidal regimes. The uptake rate constant (ku) of Cd ranged from 0.045 L g−1 d−1 to 0.109 L g−1 d−1, whereas the elimination rate constant (ke) of Cd ranged from 0.029 d−1 to 0.091 d−1. Cd bioaccumulation was slightly higher in the continuously immersed mussels than the alternately immersed mussels, but much lower than what would be expected if assuming bioaccumulation being proportional to immersion duration. Cd uptake was observed even when mussels were exposed in air, due to uptake of Cd dissolved in mantle cavity fluid and internalization of Cd adsorbed on mussel tissues. Overall, tidal height showed limited effects on Cd bioaccumulation, consistent with the trend of Cd concentrations found in X. atratus collected from different tidal heights. The mantle cavity uptake mechanism is expected to be applicable to other contaminants and bivalves, and should have important implications in risk assessments for intertidal environment.

Circular Rep encoding single stranded (CRESS) DNA virus-like sequences detected in quagga mussels (Dreissena rostriformis bugensis) and sediments from the central Lake Michigan benthos

Circular Rep Encoding Single Stranded (CRESS) DNA viruses are a diverse group of viruses that have been identified in both terrestrial and aquatic ecosystems. Recent work in the Laurentian Great Lakes characterized the ecology and diversity of CRESS-DNA viruses associated with amphipods, Diporeia spp. In the last 20 years the Lake Michigan benthos has changed considerably with drastic population declines of Diporeia spp. concurrent with an increase in invasive quagga mussel (Dreissena rostriformis bugensis) abundance. The purpose of this study was to characterize CRESS-DNA virus-like elements (VLES; which could represent complete, partial/defective, endogenized or satellite viruses) associated with both invasive quagga mussels and in sediment collected in central Lake Michigan. Viral metagenomic libraries were prepared from two size classes (>25 mm and <15 mm shell length) of Lake Michigan quagga mussels and for two different sediment layers (136 mm and 290 mm below the lake floor) in a sediment core extracted from the lake. Viral metagenomes were different between quagga mussels and sediment cores. Nine VLE sequences were present in both the quagga mussel tissues and the sediment core layers analyzed. Cs137 radiometric dating results indicate that these VLEs were present in the sediment prior to arrival of quagga mussels in Lake Michigan. These data suggest quagga mussels may interact with CRESS-DNA VLEs and algal DNA VLEs historically present in the Lake Michigan benthos. Overall, these data suggest that quagga mussels interacted with CRESS-DNA VLES present in Lake Michigan benthos since at least 1952.

Experimental exposure of the mussel Mytilus platensis (d'Orbigny, 1842) to the dinoflagellate Alexandrium catenella from Argentine Patagonia.

Individuals of Mytilus platensis were exposed to Alexandrium catenella to evaluate the accumulation and metabolization of paralytic shellfish toxins (PST) over a period of 25 days. Mussels were collected from the intertidal zone of Cerro Avanzado, Argentine Patagonia. After 16 days, the toxins in the tissues of mussels were detected by the methods of mouse bioassay and high performance liquid chromatography with fluorometric detection (HPLC-FDL). The accumulation kinetics of PST toxins in M. platensis fed with A. catenella fitted to a linear function, in which the accumulation rate was 31.2 µg STX eq kg-1 day-1. After 16 days, the PST toxin level in tissues of mussels reached 1178 µg STX eq kg-1 exceeding the safety limit for human consumption (800 µg STX eq kg-1 tissue), whereas the highest PST toxin level was reached at the end of the experimentation (1613 µg STX eq kg-1) at 25 days. Differences in the toxin profile of the dinoflagellates and the tissues of the mussels confirmed biotransformation of PST in the mussel digestive system. The toxin profile of M. platensis was dominated by the gonyautoxins GTX1 and GTX4, while the toxin profile of A. catenella was dominated by the N-sulfocarbamoyl toxin C2. To our knowledge, this is the first experimentation on a laboratory scale of PST toxins accumulation in M. platensis with a native strain of A. catenella of Argentine Patagonia.

Enzymatic and Low-Molecular Weight Parts of Antioxidant Complex in Two Species of Black Sea Mollusks with Different Resistance to Oxidative Stress: Mytilus galloprovincialis Lam. and Anadara kagoshimensis (Tokunaga, 1906)

We studied the specific features of the joint activity of the enzyme and low-molecular weight parts of the antioxidant (AO) complex in the tissues of two species of the Black Sea bivalve mollusks with different resistance to oxidative stress: a native species, the Mediterranean mussel Mytilus galloprovincialis Lam., and an invader, the ark clam Anadara kagoshimensis (Tokunaga, 1906). In the hepatopancreas and the gills and foot of mollusks, the activity of glutathione peroxidase (GP), glutathione reductase (GR), superoxide dismutase (SOD), catalase, and the level of reduced glutathione (GSH), as well as the contents of glucose, amino acids, and products that react with thiobarbituric acid (TBA-reactive products), have been analyzed. The enzyme part had a leading role in AO defense in the tissues of the Mediterranean mussel. This is indicated by higher activities of GP (hepatopancreas, gills) and SOD (hepatopancreas, foot) but a smaller content of GSH (gills, foot) as compared with ark clam. In ark clam tissues, the role of low-molecular weight part is significant, which is confirmed by the higher GSH level (gills, foot) in combination with the higher activity of GP (foot) and SOD and catalase (gills) than that observed in the Mediterranean mussel. Unlike the mussel, ark clam tissues showed a more effective joint activity of SOD, catalase, and glutathione system, which resulted in a significantly lower content of LPO products than that found in all of the studied Mediterraneanmussel tissues. These features of the joint activity of the enzyme and low-molecular weight parts of the AO complex of the Mediterranean mussel and ark clam largely determine the difference in the resistance to oxidative stress in the mollusks of these species. The results confirm the prevailing idea of the ark clam as one of the most competitive invaders as compared with native species; it has successfully mastered new biotopes in the Azov-Black Sea basin and has become an important component of benthic communities.

Assessment of accumulation of petroleum hydrocarbons by the hydrobionts of the south-eastern part of the Onega bay of the White sea

In order to assess the current state of the ecosystem of the southeast of the Onega Bay of the White Sea affected by fuel oil spill in 2003, the accumulation of petroleum hydrocarbons was analyzed by the dominant species of aquatic organisms collected on the littoral of the most polluted coast in the areas of Purnem and Lyamts villages. In 2012, samples of aquatic organisms were taken in an area where all the species discussed in this work are represented on a small area: bivalved mollusks, attached molluscs, gastropods, polychaetes. In 2013 and 2018, samples of hydrobionts were additionally selected, in the three-kilometer strip of the coast on either sides of the givin point. In 2012 and 2013, high concentrations of HC in the tissues of bivalves were recorded. In 2018, the concentrations of hydrocarbons in the tissues of the studied hydrobionts were comparable to background values. A non-parametric test of Mann-Whitney showed a significant decrease in НС in mussel tissue from 2013 to 2018, at a significance level of 0.05. Taking into account the low levels of HC in the aqueous medium (less than 1 MPC of fishfarm) and in bottom sediments (from 0.34 to 9.03 mg/kg, the median of 1.41 mg/kg) in 2018, and is comparable with the background contents of hydrocarbons in tissues of aquatic organisms. We can conclude that after 15 years of the fuel oil spill, the condition of the Cape Deep ecosystem in terms of the content of hydrocarbons returns to the baseline state, continuing emissions of oil-sand lumps do not adversely affect the ecosystem. Based on the work done, it can also be concluded that ecotoxocological methods are priority in assessing the prolonged (or delayed) accidental impact of heavy petroleum products on aquatic ecosystems. The conclusion about the presence or absence of a negative impact on the aquatic ecosystem of hydrocarbons, based solely on the analysis of abiotic components, may not be sufficiently informative because it does not take into account the accumulative and deferred effects, especially manifested in the cold Arctic waters.

The Use of Oxidative Stress Parameters of Bivalve Mollusks Dreissena polymorpha (Pallas, 1771) as Biomarkers for Ecotoxicological Assessment of Environment

The aim of this study was to investigate biomarkers of oxidative stress: сatalase (CAT), glutathione (GR), glutathione S-transferase (GST), low-molecular antioxidant—reduced glutathione (GSH) and lipid peroxide oxidation marker—malondialdehyde (MDA) and to measure heavy metal (НМ) concentrations in Dreissena polymorpha soft tissues at three different sampling sites in the Rybinsk reservoir (one of the largest in Europe) in order to assess exposure to anthropogenic pollution. The reservoir has a considerable source of pollution in its northern part due to a large industrial complex in Cherepovets. Mussels were collected at three sites which differ in the levels of anthropogenic load: more contaminated sites 1 (Cherepovets) and 2 (Koprino). Site 3 (Vesyegonsk) is relatively clean and is used as a control. In soft tissues of mussels from sites 1 and 2 significantly higher concentrations of HM (Pb, V, Cr, Ni, Cu, Mn, Zn, Cd) were detected than in mussels from site 3. Mussels from sites 1 and 2 subjected to long-term contamination from Cherepovets industry showed considerable CAT, MDA and GSH induction compared to mussels from relatively clean site 3. The correlation was found between elevated HM content and increased levels of CAT, MDA and GSH. The obtained data suggest that HM may contribute to the oxidative stress induction in mussel. MDA, CAT and GSH sensitivity in D. polymorpha demonstrated a possible use of these biomarkers in freshwater.

Ultra trace simultaneous determination of 50 polycyclic aromatic hydrocarbons in biota using pMRM GC-MS/MS

A saponification extraction method with gas chromatography pseudo-MRM (pMRM) mass spectrometry detection was developed for the determination of 50 total polycyclic aromatic hydrocarbons (TPAH50, a combination of parent and alkylated homologues) in biota. The method was aimed at monitoring and identification of potential TPAH contaminants in bitumen impacted environments. Alkylated PAHs were determined by multi-level, quantitative calibration using parent PAHs. The developed and thoroughly validated method required only one injection for TPAH50 analysis which represents significant saving of time and expensive authentic alkylated standards. The current method was tested with certified reference mussel tissue NIST 1974c and performed well. In a comparison study, the method reached a limit of quantitation (LOQ) for the TPAH50 between 0.1 and 0.2 ng g−1, while the QuEChERs enhanced matrix removal – lipid (EMR) kit produced by Agilent showed an LOQ of 5–10 ng g−1. The current method relied on response factors (RF) for the quantitation of alkylated PAHs determined against parent PAHs. These RFs were shown to be stable and consistent over the course of 1 year, during which over 200 routine environmental biota monitoring samples were analyzed. The environmental biota monitoring samples analyzed include muscle, carcass and liver, with an average total PAH50 concentration of 13, 90 and 135 ng g−1, respectively. Results show significant differences in the distributions of 1 ringed, 2 ringed, 3 ringed, 4 ringed, and 5+ ringed TPAHs between the types of biota samples.

Use of the bivalve Dreissena polymorpha as a biomonitoring tool to reflect the protozoan load in freshwater bodies

Cryptosporidium parvum, Toxoplasma gondii and Giardia duodenalis are worldwide pathogenic protozoa recognized as major causal agents of waterborne disease outbreaks. To overcome the normative process (ISO 15553/2006) limitations of protozoa detection in aquatic systems, we propose to use the zebra mussel (Dreissena polymorpha), a freshwater bivalve mollusc, as a tool for biomonitoring protozoan contamination. Mussels were exposed to three concentrations of C. parvum oocysts, G. duodenalis cysts or T. gondii oocysts for 21 days followed by 21 days of depuration in clear water. D. polymorpha accumulated protozoa in its tissues and haemolymph. Concerning T. gondii and G. duodenalis, the percentage of protozoa positive mussels reflected the contamination level in water bodies. As for C. parvum detection, oocysts did accumulate in mussel tissues and haemolymph, but in small quantities, and the limit of detection was high (between 50 and 100 oocysts). Low levels of T. gondii (1–5 oocysts/mussel) and G. duodenalis (less than 1 cyst/mussel) were quantified in D. polymorpha tissues. The ability of zebra mussels to reflect contamination by the three protozoa for weeks after the contamination event makes them a good integrative matrix for the biomonitoring of aquatic ecosystems.

Paralytic shellfish toxin profiles in mussel, cockle and razor shell under post-bloom natural conditions: Evidence of higher biotransformation in razor shells and cockles

Concentrations of the paralytic shellfish toxins GTX6, C1+2, GTX5, C3+4, dcSTX, dcNEO and dcGTX2+3 were determined by LC-FLD in composite samples of whole soft tissues of mussels (Mytilus galloprovincialis), cockles (Cerastoderma edule) and razor shells (Solen marginatus) after exposure to a Gymnodinium catenatum bloom. Specimens were harvested weekly during three months under natural depuration conditions in the Mira branch of Aveiro lagoon, Portugal. Under the decline of G. catenatum cell densities, elimination or transformation of the uptake toxins associated with the ingestion of toxic cells differed among the surveyed species. Ratio between the toxins dcSTX plus dcGTX2+3 plus dcNEO and toxins GTX6 plus GTX5 plus C1+2 plus C3+4 was used to illustrate the biotransformation occurring in the bivalves. Enhancement of the ratios was observed for razor shells and cockles seven weeks after the peak of the algal bloom. Most likely it reflects more intense biotransformation in razor shells and cockles than in mussels. Conversion into toxins of higher toxicity may prolong the bivalve toxicity. These results show the complexity of toxin elimination in bivalves under post-bloom conditions and emphasize the pertinence of monitoring programs of bivalve toxicity in order to protect human health.

Alidation of reference genes for quantitative expression analysis by qPCR in various tissues of date mussel (Lithophagalithophaga)

qPCR is a very popular method for identifying nucleotide sequences as a result of its sensitivity and relatively low cost and technical simplicity. Normalization is one of the most important steps in analyzing qPCR data and the use of reference genes is the most common normalization strategy. In the present study five commonly used reference genes (18S, 28S, ef1a, ß-act, and ?-tub) were evaluated for their stability in the mantle, gill, foot, and pallial gland of date mussel (L. lithophaga) in different seasons. Four different software packages were used for evaluation: geNorm, NormFinder, BestKeeper, and RefFinder. Although these programs contain different algorithms and analytical procedures, their ranking of the candidate reference genes was similar. Of the five selected reference genes 18S, 28S, and ef1a were determined as the three most stable in different tissues and seasons. A-tub was evaluated as the least stable reference gene and therefore inappropriate for normalization of quantitative gene expression data. The results will help improve the accuracy of gene expression analysis in samples of date mussel and at the same time provide guidance for selection of reference genes in future qPCR studies in the species.

Experimental infection of Mytilus edulis by two Vibrio splendidus-related strains: Determination of pathogenicity level of strains and influence of the origin and annual cycle of mussels on their sensitivity.

This study aimed at assessing the pathogenicity of two Vibrio splendidus-related species and evaluating the influence of the origin and annual life cycle of mussels on their sensitivity during a bacterial challenge. Thus, in vivo infection assays were made with Vibrio crassostreae 7T4_12 and Vibrio splendidus 3G1_6, over, respectively, thirteen and 9months, on adult blue mussels from five recruitment areas in France. Two bacterial concentrations were tested: one consistent with the loads of Vibrio spp. in environment and mussel tissues (~105 CFU/ml) and another one much higher (~108 CFU/ml). The tested environmental concentration has no pathogenic effect whatever the time of year, the strain used and the origin of mussels. However, at the highest concentration, a pathogenic effect was observed only at specific moments, and one of the origins appeared to be more resistant. The physiological state of mussels-depending on the time of year-seemed significant in mussels' sensitivity, as their recruitment origin. This study is the first to test the pathogenicity of V.splendidus-related strains at concentrations close to what is found in the wild, over the annual cycle of mussels, and considering their origin.

Mesocosm System to Evaluate BF-MBR Efficacy in Mitigating Oily Wastewater Discharges: an Integrated Study on Mytilus galloprovincialis.

This work presents the results of recovery efficacy of the system "BioFilm Membrane BioReactor" (BF-MBR), in the treatment of oily contaminated seawaters. To this aim, we proposed a multidisciplinary approach that integrates traditional chemical-physical measures together with the assessment on biological sentinel Mytilus galloprovincialis, maintained in a medium-scale artificial system named mesocosm. The setup included: (1) a mesocosm consisting of uncontaminated seawater; (2) a mesocosm composed of an untreated oily wastewater discharge; and (3) a mesocosm receiving the same oily wastewater previously treated by a BF-MBR pilot scale plant. The multidisciplinary approach that included traditional chemical measures on mesocosms together with the evaluation of morphological organization, mRNA expression of those genes involved in cellular stress response, immunohistochemistry and metabolomic analysis on mussel tissues, was able to provide a robust and holistic evidence of how the proposed treatment is able to reduce the overall impact of oily wastewater discharges on the marine ecosystem.

Contamination and genotoxicity biomarker responses in bivalve mussels from the major Lithuanian rivers.

European inland waters are under continuous threat of anthropogenic pollution. Determination of background level of biomarker response and subsequent classification of the impact increases the applicability of results. In the current study, we evaluate the range of chemical contamination by measuring the concentrations of metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls, and the levels of environmental genotoxicity by using the micronuclei and nuclear bud tests in bivalve mussels of the major Lithuanian rivers. Second, we aimed to evaluate the association between chemical contamination and genotoxicity biomarker responses. Finally, we set to determine the background level of genotoxic effects. Such value (summed frequency of MN and NB) was assessed-6‰. On that basis, we develop a scale of potential genotoxic impact and perform ranging sites into five categories. The results clearly indicate the existence of significant differences in the levels of chemical pollution and genotoxicity in different sites. Increased levels of studied parameters were assessed at the areas affected by municipal and industrial effluents, road runoff, combustion products, and in the area contaminated by accidental spillage. On the other hand, downstream decrease of contamination level, presumably associated with biological degradation and photochemical oxidation, were also observed. Genotoxicity parameters were associated with PAH and metal concentrations measured in mussel tissues as well as in sediments. Results also indicate that in situ genotoxicity assessment performed in the areas affected by long-term contamination of municipal origin might be not sufficiently precise. Study highlights the necessity to combine genotoxicity assessment with chemical analysis. Environ. Mol. Mutagen. 61:338-354, 2020. © 2019 Wiley Periodicals, Inc.

Forms of mercury in the Baltic mussel (Mytilus trossulus): Human and ecosystem health risk assessment

Mercury (Hg) is one of the most dangerous environmental pollutants. A significant source of this toxic element to the human body is the consumption of seafood - including the increasingly popular mussels. Mussels also play an important role in the marine ecosystem, providing a food base for fish and birds. The study aimed to determine the level of total Hg and its labile and stable forms in the Baltic mussel (Mytilus trossulus), as well as to indicate the factors that shape them. The research was conducted in the Puck Bay (Polish part of the southern Baltic Sea) in 2012–2013. The study material consisted of M. trossulus mussels, the components of their diet (suspended matter and phytoplankton), and surface sediments. Concentrations of total Hg (HgTOT) and the individual Hg forms were established using the thermodesorption method on a DMA-80 analyser (Milestone). The obtained results showed that the level of Hg concentration in M. trossulus from the Puck Bay was shaped by the individual features of specimens, related to the growth and reproductive cycle of mussels, as well as the quality of food consumed by them. The total share of labile Hg forms in M. trossulus was high, exceeding 90% of HgTOT, and the predominant form was the most dangerous organic Hg. This means that almost all of the Hg accumulated in mussels can be transferred to higher trophic levels. The obtained results showed that Baltic mussels were characterised by levels of HgTOT and organic Hg deemed to be safe for humans. A positive relationship was noted between the HgTOT concentration in a mussel's tissues and the length of its shell. Smaller sized organisms demonstrated not only by lower Hg concentrations, but also by better condition and, consequently, higher nutritional value.