Relationship between shell weight and cadmium content in whole digestive gland of the Japanese scallop Patinopecten yessoensis (Jay)

Seasonal and age-specific variations of cadmium (Cd) concentration in the digestive gland were investigated in the Japanese scallop Patinopecten yessoensis from Peter the Great Bay, Sea of Japan, with different degrees of Cd pollution. The seasonal changes in Cd concentrations of the digestive gland were inversely proportional to the dry weight of the gland. Concentrations of Cd and total Cd content (mug Cd per organ) increased with age (age-specific) to the same extent in contaminated and uncontaminated areas. There was also a strong positive correlation between Cd content in the whole digestive gland and shell weight and it is proposed that this relationship can be used as a new criterion for comparative evaluation of Cd levels in scallops from different areas We hypothesize that Cd is uptaken into scallops in proportion to the amount of calcium that absorbed through ion channels, and in addition, Cd in the digestive gland is in immobile forms (e.g. metal-rich granules) that accumulate with age. Moderate environmental pollution has no effect on the relationship between Cd content and shell size and the observed decrease in growth performance of the scallops from polluted areas may be due to other factors.     

Significance of metallothioneins and lysosomes in cadmium toxicity and homeostasis in the digestive gland cells of mussels exposed to the metal in presence or absence of phenanthrene

Metallothioneins and lysosomes are known to be involved in cellular detoxication and sequestration of certain metals^1–3 and both have been identified in this role in elimination of copper from marine mussels (Mytilus edulis/galloprovincialis).³ Cadmium (Cd), however, has been shown to persist in the cells of the digestive gland for long periods with only minimal elimination. An experiment was designed to test the effects of Cd on the fragility of lysosomal membranes in the digestive cells as a measure of cellular injury,^4,5 metallothionein content of the digestive gland and cadmium concentration in this organ. Phenanthrene was used also to destabilise lysosomal membranes⁶ in order to test if increased lysosomal fragility interfered with cadmium metabolism and detoxication. The results demonstrated that Cd induced metallothionein synthesis and that elimination of Cd was minimal after 28 days in clear seawater. Lysosomal fragility was initially increased but this effect was soon reversed, even with continued exposure to Cd. The lysosomal destabiliser, phenanthrene, did not appear to affect accumulation of Cd or levels of metallothionein.     

Effects of linear alkylbenzene sulphonate (LAS) and cadmium in the digestive gland of mussel, Mytilus sp.

A laboratory study was carried out exposing mussels (Mytilus sp.) to linear alkylbenzene sulphonate (LAS) (6 mg litre⁻¹), Cd (0.05 mg litre⁻¹) and LAS plus Cd at the same concentrations. The aim was to assess the use of several histopathological and biochemical indices as potential biomarkers of the impact of these xenobiotics in the digestive gland of molluscs. Treated mussels actively accumulated Cd in the digestive gland compared with controls (p 0.01), the highest levels occurring after 30 days of exposure in the group treated with Cd plus LAS. Among several histological alterations screened in digestive gland tissues the thickness of digestive tubules in Cd treated animals decreased more markedly (p 0.01) than in LAS exposed mussels. As for biochemical parameters, the investigated antioxidant enzyme activities, superoxide dismutase (SOD), catalase, DT-diaphorase and glutathione peroxidase (GPX) did not show any significant induction due to these xenobiotics. However, a slight decrease of the antioxidant defences of the animals was detected after 30 days of exposure to contaminants.     

Cadmium and zinc concentrations in zooplankton in the subarctic region of the North Pacific

Cadmium and zinc concentrations were determined in 10 species of pelagic zooplankton collected in the northern North Pacific, the Bering Sea, the Okhotsk Sea and off Hokkaid?, during the summers of 1974–1976. The mean cadmium contents in euphausiids, copepods, and amphipods were 1.16μg/g dry wt (range: 0.36–2.17μg/g), 6.63μg/g (1.66–14.55μg/g), and 8.28μg/g (2.83–14.50μg/g), respectively. Cadmium in euphausiids was significantly lower in concentration than in the other two crustacean groups. The difference in cadmium levels among the crustacean groups is discussed on the basis of feeding habits and physiological characteristics of the zooplankton. Zinc levels in the crustaceans were similar, with values around 100μg/g (range: 59–195μg/g). Both cadmium and zinc concentrations in euphausiids taken from coastal waters off Hokkaid? were significantly higher than those from the Bering Sea and the northern North Pacific. This trend may reflect coastal pollution rather than characteristics of the species. Contribution No. 117 from the Research Institute of North Pacific Fisheries, Faculty of Fisheries, Hokkaido University     

Immuno-localisations (GSSP) of subcellular accumulation sites of phenanthrene, aroclor 1254 and lead (Pb) in relation to cytopathologies in the gills and digestive gland of the mussel Mytilus edulis

Cell and tissue pathology of both, gill and digestive tissue, has been the subject of many studies for the elucidation of contaminant-induced biological effects. In the present study, cellular pathological alterations were linked to subcellular sites of chemical accumulation in gills and digestive gland tissues. For this purpose, mussels (Mytilus edulis) were exposed to the organic contaminants aroclor 1254 (PCB) (20 microg/L), phenanthrene (PAH) (150 microg/L) or the metal lead (Pb) (2.5mg/L). The localization of chemicals at the subcellular level was analysed by an antibody-based detection system (GSSP) by the use of commercially available antibodies specifically directed against the chemicals. Pathological changes were analysed in parallel in identical samples by transmission electron microscopy. After exposure to the different contaminants, cell organelles such as mitochondria, the endo-lysosomal system as well as endoplasmic reticulum showed clear evidence of chemically-induced alterations. Large numbers of crystalloid inclusions were found in mitochondria and in autophagic lysosomes as well as multi-lamellated whorls after PAH and aroclor exposure. Immunocytochemical detection of the chemicals showed their accumulation inside of various cell organelles such as lysosomes, mitochondria, and nuclei. Additionally, chemicals were localized in association to membranes, cilia and microvilli of gill and digestive gland cells. Furthermore, the chitinous rod and mucus secretions of gill epithelial cells were positively labelled for contaminants indicating their role in protection. Localization of contaminants by immuno-detection in combination with pathological diagnosis gives insights into the cellular targets of chemical attack.     

Studies on isoenzymes of glutathione S-transferase in the digestive gland of Mytilus galloprovincialis with exposure to pollution

The possible utility of glutathione S-transferase isoenzymes in affinity purified extracts of digestive gland from Mytilus galloprovincialis as indicators of exposure to organic pollution has been assessed by fast protein liquid chromatography (FPLC) using a Mono-Q ion exchange column. Four main peaks of protein (isoenzymes 1–4) were detected in these chromatographic studies all of which displayed detectable catalytic activity with 1-chloro-2,4-dinitrobenzene and glutathione as substrates. The bulk of the activity with these substrates was associated with isoenzyme 1. The specific activity of cytosolic extracts from six sites in Venice Lagoon and the Adriatic Sea (UNESCO-MURST Venice Lagoon Ecosystem Project) decreased slightly with increasing tissue levels of chemical contaminants (hydrocarbons, PCBs and organochlorines). FPLC of affinity purified extracts from three of these sites was used to assess the possible variation in the levels of individual isoenzymes relative to pollution status. No difference was observed in the levels of these isoenzymes.     

Cadmium bioconcentration in the echinoid Paracentrotus lividus: Influence of the cadmium concentration in seawater

Uptake and loss kinetics of cadmium were studied in Paracentrotus lividus exposed for 24 d to different stable Cd concentrations (0 to 1.14 μg Cd l⁻¹) and ¹⁰⁹Cd tracer added to seawater. The whole-body uptake kinetics were linear over the time course of the experiment. The whole-body ¹⁰⁹Cd concentration factor was independent of the stable Cd concentration in ambient seawater. Bioconcentration of Cd in whole individuals and their body compartments was directly proportional to the Cd concentration added to the seawater. The echinoid digestive tract wall showed the highest degree of Cd uptake. Whole-body loss kinetics were described by a 2-component exponential equation. The loss kinetics were similar for each of the treatments examined. Cadmium was found to display a long biological half-life in echinoid tissues; the major fraction (73 to 85%) of the Cd taken up by echinoids was eliminated following a loss component whose biological half-life was of the order of 1 year, regardless of the absolute Cd concentration accumulated by the echinoid. Paracentrotus lividus is suggested as a valuable biomonitor of Cd, particularly where knowledge of Cd concentration variations over long-term is of interest.     

Sulfide control of cadmium and copper concentrations in anaerobic estuarine sediments

Equilibrium concentrations of the toxic trace metals copper and cadmium were calculated for the physico-chemical conditions characterizing pore waters of anaerobic estuarine sediments using available thermodynamic data and assuming simple sulfide minerals control solubilities. Polysulfide complexes are responsible for the solubility of copper in the cuprous (Cu(I)) oxidation state. Predicated copper concentrations, assuming covellite (CuS) is the controlling solid phase, are in reasonable agreement with copper analyses in a wide range of sulfidic waters and sediment pore waters. In the absence of thermodynamic data, no account could be taken of possible polysulfide complexes of cadmium. However, bisulfide complexes appear to account satisfactorily for observed solubilities assuming the existence of greenockite (CdS) as the controlling solid phase. Anaerobic estuarine sediments may act as a sink for copper and cadmium in the common situation in which free sulfide concentrations are controlled by the coexistence of iron sulfide and iron oxide minerals. However, where free sulfides reach high concentrations of 10^?3 M or more, the concomitant increase in concentration of bisulfide and polysulfide complexes may result in the sediments acting as a source of copper and cadmium.     

Oxidative stress generated by diesel seawater contamination in the digestive gland of the Antarctic limpet Nacella concinna

The aim of this work was to investigate the activity of antioxidant enzymes and oxidative damage in the digestive gland of the limpet Nacella concinna, and their suitability as biomarkers for hydrocarbon pollution in Antarctic coasts. Three groups of 30 individuals each were kept in seawater containing 0%, 0.05% or 0.1% diesel. Superoxide dismutase, catalase, glutathione S transferase and glutathione peroxidase activities, as well as lipid peroxidation and protein oxidation were studied in 18 animals of each group after 24, 48 and 168 h of exposure. The activity levels of most enzymes were increased by diesel in a dose-dependent manner. Glutathione peroxidase showed the most clear effect; its activity significantly increased in the 0.1% diesel group respect to the control. Lipid peroxidation and protein oxidation were significantly increased by diesel after 168 h. Both variables were higher in the group exposed to the lowest dose.     

Seasonal variations in dimethylsulfoniopropionate and dimethylsulfide concentrations in relation to the plankton community in the St. Lawrence Estuary

Weekly variations in total dimethylsulfoniopropionate (DMSPt) and dimethylsulfide (DMS) were investigated in relation to the phytoplankton assemblage from spring to fall 1994 at a coastal fixed station in the St. Lawrence Estuary. DMSPt and DMS concentrations showed a strong seasonality and were tightly coupled in time. Maximum concentrations of DMSPt and DMS were observed in July and August, during a period of warm water and low nutrient concentrations. Seasonal maxima of 365.4 nmol l⁻¹ for DMSPt and 14.2 nmol l⁻¹ for DMS in early August coincided with the presence of many phytoplankton species, such as Alexandrium tamarense, Dinophysis acuminata, Gymnodinium sp., Heterocapsa rotundata, Protoperidinium ovatum, Scrippsiella trochoidea, Chrysochromulina sp. (6 μm), Cryptomonas sp. (6 μm), a group of microflagellates smaller than 5 μm (mf < 5), many tintinnids, and Mesodinium rubrum. The abundance of mf < 5 followed the general trend of DMS concentrations. The temporal occurrence of high P. ovatum abundance and DMSPt concentrations suggests that this heterotrophic dinoflagellate can either synthesize DMSP or acquire it from DMSP-rich prey. The calculated sea-to-air DMS flux reached a maximum of 8.36 μmol ⁻² d⁻¹ on August 1. The estimated annual emission from the St. Lawrence Estuary is 77.2 tons of biogenic sulfur to the atmosphere.     

A computational model of the digestive gland epithelial cell of marine mussels and its simulated responses to oil-derived aromatic hydrocarbons

This paper describes a computational model of digestive gland epithelial cells (digestive cells) of marine mussels. These cells are the major environmental interface for uptake of contaminants, particularly those associated with natural particulates that are filtered from seawater by mussels. Digestive cells show well characterised reactions to exposure to lipophilic xenobiotics, such as oil-derived aromatic hydrocarbons (AHs), which accumulate in these cells with minimal biotransformation. The simulation model is based on processes associated with the flux of carbon through the cell. Physiological parameters such as fluctuating food concentration, cell volume, respiration, secretion/excretion, storage of glycogen and lipid, protein/organelle turnover (autophagy/resynthesis) and export of carbon to other tissues of the mussel are all included in the model. The major response to AHs is induction of increased autophagy in these cells. Simulations indicate that the reactions to AHs and food deprivation correspond well with responses measured in vivo.     

Microbial respiration in the Levantine Sea: evolution of the oxidative processes in relation to the main Mediterranean water masses

First data on microbial respiration in the Levantine Sea are reported with the aim of assessing the distribution of oxidative processes in association with the main Mediterranean water masses and the changing physical structure determined by the Eastern Mediterranean Transient. Respiratory rates, in terms of metabolic carbon dioxide production, were estimated from measured electron transport system activities in the polygonal area of the Levantine Sea (32.5–36.5 N Latitude, 26.0–30.25 E Longitude) and at Station Geo’95, in the Ionian Sea (35°34.88 N; 17°14.99 E). At the Levantine Sea, the mean carbon dioxide production rate decreased from the upper to the deeper layers and varied from 22.0±12.4 μg C h⁻¹ m⁻³ in the euphotic layer to 1.30±0.5 μg C h⁻¹ m⁻³ in the depth range between 1600 and 3000 m. Significant differences were found among upper, intermediate and bottom layers. The euphotic zone supported a daily carbon dioxide production of 96.6 mg C d⁻¹ m⁻² while the aphotic zone (between 200 and 3000 m) sustained a 177.1 mg C d⁻¹ m⁻² carbon dioxide production. In Station Geo’95, the carbon dioxide production rates amounted to 170.4 and 102.2 mg C d⁻¹ m⁻² in the euphotic and aphotic zones, respectively. The rates determined in the identified water masses showed a tight coupling of respiratory processes and Mediterranean circulation patterns. The increasing respiratory rates in the deep layers of the Levantine Sea are explained by the introduction of younger waters recently formed in the Aegean Sea.     

A carbon and nitrogen flux model of mussel digestive gland epithelial cells and their simulated response to pollutants

The mussel digestive gland epithelial cells provide a key interface between the organism and pollutants such as aromatic hydrocarbons. The simulation of their uptake and export mechanisms as well as an internal protein degradation pathway, and any subsequent disruption to any of them, has been undertaken. A computational model is described, which simulates the flow of carbon and nitrogen through a mussel's digestive cell. The model uses a compartmentalised view of the cell with inviolate 'pipelines' connecting each of the volume-variable partitions. Only the major physiological pathways relevant to the flow of either carbon or nitrogen or volume are modelled. Simulated response to hydrocarbon exposure is examined.     

Use of the Comet assay to assess DNA damage in hemocytes and digestive gland cells of mussels and clams exposed to water contaminated with petroleum hydrocarbons

Oil spills can result in the deposition of large quantities of petroleum hydrocarbons into intertidal and shallow waters seriously impacting bivalve populations. Petroleum hydrocarbons are enriched in polycyclic aromatic hydrocarbons (PAH) and PAH analogs many of which may have potential to damage DNA. The Comet assay is useful for assessing DNA damage and has been used to a limited degree with aquatic organisms, but mostly with studies in vitro. We have carried out studies with the Comet assay to assess the DNA damaging potential of complex mixtures of petroleum hydrocarbons for bivalves. Experiments were carried out with mussels (Mytilus edulis) and clams (Mya arenaria) with dispersions and water soluble fractions of an Arabian crude oil which was also chemically characterized in detail by GC-MS. Pilot studies were first conducted to evaluate test performance and reproducibility. An interindividual coefficient of variation ranging from 17 to 30% was established for the assay with hemocytes and digestive gland cells of both species. Exposure to hydrocarbon fractions had no significant impact on clams. However, an increase in DNA damage was observed at P < 0.1 with digestive gland cells of mussels exposed to aqueous fractions of a light crude oil. These studies have demonstrated a potential for DNA damage in bivalves exposed to oil spills in inshore waters as well as potential for interspecies sensitivity.     

Effects of tributyltin at environmental levels on monooxygenase system of digestive gland in hard clam Meretrix meretrix

The effects on ethoxyresorufin O-deethylase (EROD), NADPH-cytochrome c reductase and NADH cytochrome b5 reductase activities of digestive gland in Meretrix meretrix exposed to tributyltin (TBT) at environmental levels (0.1,1.0, 10.0 ng/dm3 as stannum concentration), in experimental condition, were evaluated. The EROD, NADH cytochrome b5 reductase activities were significantly inhibited after exposure to 10.0 ng/dm3 TBT for 8 and 20 d, the NADPH cytochrome c reductase activities were significantly inhibited after exposure to 0.1,1.0 and 10.0 ng/dm3 TBT for 8 d and to 1.0 and 10.0 ng/dm3 for 20 d, as compared with the matched control, while NADH cytochrome b5 reductases and NADPH cytochrome c reductase activities were induced after exposure to 10.0 ng/dm3 TBT for 2 d. The EROD activity in the 10 ng/dm3 group, and the NADH cytochrome b5 reductases activities in 1.0 and 10.0 ng/dm3 groups, were significantly induced when transferred to clean recovery tanks for 7 d. The three enzymic activities in the clams exposed to TBT were recovered to the level corresponding to that of the control group after transfer to clean recovery tanks for 20 d. NADPH cytochrome c reductase activity in Meretrix meretrix seems to be more sensitive to exposure of TBT than that of the EROD and NADH cytochrome b5 reductases. The results suggest that induction and inhibition by TBT to the monooxygenase system enzymic activity in Meretrix meretrix would simultaneously exist. The enzymic activities were inhibited by exposure for a long time. The results suggest that inhibition of the monooxygenase system should be an indication of the exposure to environmentally relevant concentrations of TBT for a long time.