Genotoxicity of copper oxide and silver nanoparticles in the mussel Mytilus galloprovincialis

Though there is some information on cytotoxicity of copper nanoparticles and silver nanoparticles on human cell lines, there is no information on their genotoxic and cytotoxic behaviour in bivalve molluscs. The aim of this study was to investigate the genotoxic impact of copper oxide and silver nanoparticles using mussels Mytilus galloprovincialis. Mussels were exposed to 10 μg L⁻¹ of CuO nanoparticles and Cu²⁺ and Ag nanoparticles and Ag⁺ for 15 days to assess genotoxic effects in hemocytes using the comet assay. The results obtained indicated that copper and silver forms (nanoparticles and ionic) induced DNA damage in hemolymph cells and a time-response effect was evident when compared to unexposed mussels. Ionic forms presented higher genotoxicity than nanoparticles, suggesting different mechanisms of action that may be mediated through oxidative stress. DNA strand breaks proved to be a useful biomarker of exposure to genotoxic effects of CuO and Ag nanoparticles in marine molluscs.     

Accumulation and effects of organotin compounds in oysters and mussels: Correlation with serum biochemical and cytological factors and tissue burdens

Oysters and mussels exposed to a concentration of 0·7 ppb (μg/liter) tributyltin from painted panels in flowing seawater accumulated tin in the digestive glands to comparable levels. The mussels experienced approximately 50% mortality during the 60-day test period, but the oysters suffered virtually no deaths. There was no evidence from either bivalve of elevated numbers of hemocytes during the test period and no evidence for cellular disruption as detected by increased levels of serum lysosomal hydrolases. Serum protein of exposed mussels relative to controls increased with time of exposure to the toxicant, while oyster serum protein, normally 10 x higher than in mussels, did not. No evidence was found for elevated stress proteins (heat shock proteins) or metallothioneins in the serum hemocytes of either bivalve. Responses by these animals to fatal or near fatal doses of TBT were thus very different from responses to copper that we have reported elsewhere.^1,2     

Quantitative determination of lysozyme in the hemolymph of Mytilus edulis by the enzyme-linked immunosorbent assay (ELISA)

The defensive responses of the bay mussel, Mytilus edulis, to invading organisms and toxicants is primarily cellular. Hemolymph cells as well as the other organs and tissues of the mussel through their normal functioning and interactions with toxic substances influence the chemical composition of the animal's hemolymph. It has been found that the levels of specific molecules in the hemolymph fluctuate as a consequence of trace metal insult. It was proposed that one way in which trace metal toxicity may be expressed is through an influx of free lysosomal hydrolases in the hemolymph.Reported here is the development of an enzyme-linked immunosorbent assay (ELISA) with which micro-samples of mussel hemolymph can be analyzed quantitatively for the lysosomal hydrolytic enzyme, lysozyme. During development comparisons were made of the results acquired by spectrophotometric determinations of lysozyme activity and ELISA-determined lysozyme concentrations in the hemolymph of mussels. The hemolymph from unstressed and copper-stressed mussels was examined. It was found that the overall trends in lysozyme fluctuations were indicated by both techniques. However, on occasion in copper-stressed populations a divergence between the two sets of data was observed. This suggested an effect of copper on lysozyme molecular configuration.     

Partitioning of copper among copper-binding proteins in the mussel Mytilus edulis exposed to soluble copper

Partitioning of copper among copper-binding proteins was evaluated in digestive glands of Mytilus edulis exposed to soluble copper. Groups of mussels were held in flow-through bioassay systems and exposed to 25 μg Cu liter^?1 for up to 21 weeks. At three-week intervals, groups of 25 mussels were removed and the digestive glands were analyzed for copper-binding proteins by gel-permeation chromatography and atomic absorption spectrometry.Chronic exposure to copper resulted in increased amounts of copper in the low molecular weight (LMW) protein fraction, which contains metallothioneins, and in the high molecular weight (HMW) protein fraction, which contains metalloenzymes. Concentrations of copper in the LMW protein fraction increased and then appeared to plateau with long exposure times, whereas those in the HMW protein fraction continued to increase with exposure time.     

The role of oxyradicals in intracellular proteolysis and toxicity in mussels

Studies were performed on the common mussel, M. edulis L., to determine whether copper (Cu) exposure can affect the extent to which digestive cell proteins are oxidised and whether such oxidative damage is mediated by free radicals. Three age groups of mussels were exposed for 6 ^-days to environmentally realistic concentrations of Cu and then digestive gland homogenates were examined for evidence of protein carbonyl formation. Significant increases in carbonyls relative to untreated control mussels were seen for the youngest (2–4 year-old) and oldest (≥ 10 year-old) mussels only after exposure for 6 days, followed by recovery from exposure for a further 6 days. Untreated mussels also showed an age-related difference in protein oxidation, with a significantly lower concentration in the youngest animals (2–4 year olds). Copper did not affect the levels of modified tryptophan or tyrosine residues or the extent of total lipid peroxidation in digestive gland homogenate. Significant depletion of total vitamin E (a-tocopherol) was seen only in young and medium-aged mussels following exposure for 6 days. The levels of protein carbonyl groups were increased in digestive cell cytosol and lighter lysosomes but not in heavier lysosomes or digestive gland microsomes following 5 days exposure to Cu. Dihydrohodamine-123 was converted to fluorescent rhodamine-123 following sequestration into digestive cell lysosomes. The results suggest a link between the lysosomal sequestration of copper, a concomitant increase in the production of oxyradicals and the potential for intracellular oxidative damage, as well as an increased capacity for oxidative damage in older animals.     

皱纹盘鲍血细胞吞噬发光的研究

于１９９８年７月从大连碧龙海珍品有限公司购得人工养殖的皱纹盘鲍,运用化学发光法研究在体外条件下利用６种活性氧清除剂ＳＯＤ（超氧化物歧化酶）、ＣＡＴ（过氧化氢酶）、苯甲酸钢和ＤＭＦ（二甲基呋喃）、ＮＢＴ（硝基四唑蓝）及金属螯合济ＥＤＴＡ（乙二胺四乙酸）等试齐对皱纹盘鲍血细胸吞噬活动中化学发光的产生和影响。结果表明,活性氧清除剂对皱纹盘鲍血细胞的吞噬发光都有掏作用,说明皱纹盘鲍血细胞在吞噬活动中能够释     

Responses of the mussel Mytilus edulis to copper and phenanthrene: Interactive effects

Most investigations of the responses of marine organisms to xenobiotics have concentrated on single contaminants and little is known of possible interactive effects of different classes of xenobiotics. As these latter seldom occur in environmental isolation, it is important to understand any interactions (synergistic or antagonistic) which may occur. This problem has been approached in the mussel Mytilus edulis by exposing estuarine mussels to copper (20 μg litre⁻¹) and phenanthrene (100 μg litre⁻¹) both individually and in combination, and measuring cytochemical subcellular and physiological responses after 3 days exposure and 3 days and 12 days recovery period. Results showed that mussels accumulated both xenobiotics during 3 days exposure. Depuration of copper was complete in 3 days recovery period, while loss of phenanthrene ranged from 30% to 70% of the concentration reached after 3 days exposure. There were no interactive effects on depuration.Both copper and phenanthrene reduced lysosomal hydrolase latency in digestive cells, and copper appeared to have a synergistic effect in preventing recovery of latency of lysosomal N-acetyl-β-hexosaminidase during the recovery period. There was evidence, in the digestive cells, of an antagonistic effect of copper on stimulation of activity of the microsomal respiratory chain (measured as NADPH-neotetrazolium reductase) by phenanthrene. Stimulation of this system by phenanthrene persisted after 12 days recovery period. There was a synergistic interaction of copper and phenanthrene on elevation of oxygen consumption and ammonium excretion. Clearance rates and scope for growth (physiological condition) were depressed by copper but not by phenanthrene after 3 days exposure.These findings are discussed in terms of known effects of copper and phenanthrene and the interactions are considered in terms of environmental effects measurements.     

Solvent extraction of copper acetylacetonate in studies of copper(II) speciation in seawater

A liquid-liquid partition, ligand exchange procedure involving the formation of copper(II) complexes with acetylacetone is presented for the determination of stability constants and concentrations of copper chelators in seawater. Acetylacetone competes with natural ligands for copper, and the equilibrium concentration of the copper acetylacetonate complex is used in speciation calculations. The concentration of the complex is calculated by partitioning a fraction of it into an organic phase and determining the total Cu concentration in that phase by back extracting with acid, and analyzing by flameless atomic absorption spectroscopy. The concentration of Cu acetylacetonate in seawater in equilibrium with the organic phase is calculated from the partition coefficient. The simple, thermodynamically well characterized procedure offers several advantages over previous techniques. Studies using organic free seawater and model ligands show good agreement between experimental and calculated conditional stability constants. Studies from seawater in Biscayne Bay, Florida, indicate two ligand types are present; type 1, K₁ = 1.2 × 10¹², C_L1 = 5.1 × 10⁻⁹ M; type 2, K₂ = 2.8 × 10¹⁰, C_L2 = 1.1 × 10⁻⁷ M. Speciation is dominated by ligand type 1. Depth profiles of [Cu(II)]_free/[Cu(II)]_total measured with the procedure at ambient copper concentrations show an increase from < 5 × 10⁻⁵ at 50–60 m to > 1 × 10⁻³ at the surface at two stations off the Florida coast.     

Complexation of copper and nickel in the dissolved phase of marine sediment slurries

Speciation of copper and nickel in the water phase of incubated marine slurries under aerobic conditions was performed with MnO₂ and Sep—Pak C₁₈ cartridges. Changes in time during the incubations of concentrations of dissolved organic carbon (DOC), dissolved copper and nickel and inorganic nitrogen were followed. The influence of organic complexation on the dissolved concentrations of copper and nickel was investigated as well as competition between copper and nickel for dissolved organic ligands.Two pools of dissolved organic ligands could be distinguished. With the MnO₂ method a relatively strong ligand group was determined that was subjected to degradation. The conditional stability constant for copper with the relatively strong ligand was 10^11.1. The conditional stability constant for the relatively strong nickel ligand was difficult to determine due to saturation of the ligand sites; it was found to be around 10¹⁰. However, it could not be ascertained whether nickel was reversibly com-plexed with the organic ligands.With Sep—Pak a relatively weak Hgand group was detected that was probably more resistant to degradation. The conditional stability constant of the weaker ligand could not be estimated, an approximation revealed that it was weaker than the ligand group determined with the MnO₂ method. For copper the difference between binding strength of the ligand groups was at least 100, for nickel the difference was less.Competition between copper and nickel for the ligands could not be detected. Only during the first day of the experiment, when the system was not in equilibrium was competition suspected. However, the replacement of nickel by copper from the ligand sites was not straightforward and could not be accounted for by our model.The concentration of total dissolved copper during the first week of the experiment was found to be controlled on the one hand by release from the sediment of copper already associated with dissolved organic matter (DOM) and on the other hand by concentration of the strongest ligand. The calculated free copper concentration increased from 10⁻¹² to 10⁻⁹mol l⁻¹ due to the oxidation of the strongest ligand. After saturation of the strongest ligand the relatively weak ligand controlled the free copper concentration. A continuing release of copper from the sediment by degradation of particulate organic matter (POM) will not increase the free copper concentration until the ligand sites of the weaker ligands get saturated.The total dissolved nickel concentration seemed only to be determined by the sum of the concentrations of the organic ligands. A degradation of ligands resulted in a decrease of the total dissolved nickel concentration. The calculated free nickel concentration did not change with time.     

Metabolic conversion of toluene and ethylbenzene by pacific salmon microsomal preparations

The aromatic fraction from crude oil has a substantial solubility in water and as a result makes up the major hydrocarbon components of processed ballast water.^1,2 The purpose of this study was to investigate the metabolism of several of the major components of this processed water by Chinook salmon, Oncorynchus tschawytscha, liver microsomes. The metabolic products of toluene and ethylbenzene in this microsomal system, as determined by gas chromatography-mass spectrometry, were benzyl alcohol and 1-phenylethanol, respectively. The conditions for the microsomal incubations were 20°C, pH 7·5, and an ionic strength of 0·126. A linear rate of benzyl alcohol and 1-phenylethanol formation is observed during the first 30 to 60 min followed by a decrease in the rate between 60 and 90 min.     

Kinetic and equilibrium studies of copper-dissolved organic matter complexation in water column of the stratified Krka River estuary (Croatia)

An interaction of dissolved natural organic matter (DNOM) with copper ions in the water column of the stratified Krka River estuary (Croatia) was studied. The experimental methodology was based on the differential pulse anodic stripping voltammetric (DPASV) determination of labile copper species by titrating the sample using increments of copper additions uniformly distributed on the logarithmic scale. A classical at-equilibrium approach (determination of copper complexing capacity, CuCC) and a kinetic approach (tracing of equilibrium reconstitution) of copper complexation were considered and compared. A model of discrete distribution of organic ligands forming inert copper complexes was applied. For both approaches, a home-written fitting program was used for the determination of apparent stability constants (K_i^equ), total ligands concentration (L_iT) and association/dissociation rate constants (k_i¹,k_i^- 1).A non-conservative behaviour of dissolved organic matter (DOC) and total copper concentration in a water column was registered. An enhanced biological activity at the freshwater–seawater interface (FSI) triggered an increase of total copper concentration and total ligand concentration in this water layer. The copper complexation in fresh water of Krka River was characterised by one type of binding ligands, while in most of the estuarine and marine samples two classes of ligands were identified. The distribution of apparent stability constants (log K₁^equ: 11.2–13.0, log K₂^equ:8.8–10.0) showed increasing trend towards higher salinities, indicating stronger copper complexation by autochthonous seawater organic matter.Copper complexation parameters (ligand concentrations and apparent stability constants) obtained by at-equilibrium model are in very good accordance with those of kinetic model. Calculated association rate constants (k₁¹:6.1–20 × 10³ (M s)^− 1, k₂¹: 1.3–6.3 × 10³ (M s)^− 1) indicate that copper complexation by DNOM takes place relatively slowly. The time needed to achieve a new pseudo-equilibrium induced by an increase of copper concentration (which is common for Krka River estuary during summer period due to the nautical traffic), is estimated to be from 2 to 4 h.It is found that in such oligotrophic environment (dissolved organic carbon content under 83 µM_C, i.e. 1 mg_CL^− 1) an increase of the total copper concentration above 12 nM could enhance a free copper concentration exceeding the level considered as potentially toxic for microorganisms (10 pM).     

Oxidation of copper(I) in seawater at nanomolar levels

The oxidation and reduction of nanomolar levels of copper in air-saturated seawater and NaCl solutions has been measured as a function of pH (7.17–8.49), temperature (5–35 °C) and ionic strength (0.1–0.7 M). The oxidation rates were fitted to an equation valid at different pH and ionic strength conditions in sodium chloride and seawater solutions:

The reduction of Cu(II) was studied in both media for different initial concentrations of copper(II). When the initial Cu(II) concentration was 200 nM, the copper(I) productions were 20% and 9% for NaCl and seawater, respectively. The effect of speciation of copper(I) reduced from Cu(II) on the rates was studied. The Cu(I) speciation is dominated by the CuCl₂⁻ species. On the other hand, the neutral chloride CuCl species dominates the Cu(I) oxidation in the range of 0.1 M to 0.7 M chloride concentrations.     

Factors influencing biodeposit production by the New Zealand freshwater mussel Echyridella menziesii

Laboratory experiments on the New Zealand freshwater mussel Echyridella menziesii were used to investigate the short-term effects (7–8 days) of food type on rates of biodeposition and benthic substrate respiration. Post-feeding biodeposition rates ranged from 0.34 to 1.52?mg?g^?1?h^?1 (mean?=?0.50?mg g^?1?h^?1) and were unaffected by the addition of toxin-producing Microcystis. Addition of suspended sediment (30?mg?L^?1) visibly altered substrate composition, and increased total and inorganic biodeposit production rates by 24–33% compared to mussels fed commercial phytoplankton stock. Biodeposition rates of mussels in lake bed substrates were 38% higher than those in silica sand for identical feeding regimes, suggesting that a significant proportion of material produced in this experiment could have been derived from feeding on organic matter in the lake bed sediments. Respiration rates were higher in treatments with Microcystis but were unaffected by the presence of mussels. This laboratory study suggests that biodeposition by E. menziesii is resilient to short-term exposure to Microcystis, and highlights the ability of mussels to alter benthic substrate composition by incorporating suspended sediment into substrates.     

Effects of long-term exposure to silver or copper on growth, bioaccumulation and histopathology in the blue mussel Mytilus edulis

The purpose of this study was to determine the long-term accumulation of either silver or copper from low concentrations in seawater by blue mussels, Mytilus edulis. Mussels raised from eggs in the laboratory to the age of 2·5 months (approximately 4·5 mm in length) were continuously exposed to 0, 1, 5 and 10μg/liter of either silver (nitrate) or copper (chloride) and sampled at 12, 18 and 21 months for growth studies, measurements of metal accumulation and histopathological examination.Whole-body soft tissues were analyzed for the presence of both silver and copper, as background levels of copper in the incoming seawater averaged 2–4 μg/liter. Mussels exposed to silver had accumulated significant amounts of silver only at the highest test concentration (10 μg/liter Ag) after 12 months, but at 18 and 21 months significant levels were accumulated at all three test concentrations. Mussels exposed to copper accumulated significant amounts of copper at 5 and 10 μg/liter Cu after all three sampling periods, but not at 1μg/liter. Silver-exposed animals also accumulated significantly greater amounts of copper than control animals.In a comparative study, field-collected juvenile mussels (approximately 16·1 mm in shell length) and adult mussels (approximately 53·4 mm in shell length) were exposed for 12 months to 0, 5, 25 and 50 μg/liter silver only and subsequently sampled for metal-accumulation analyses and growth measurements. Juvenile mussels accumulated significant amounts of silver at all test concentrations, with the exception of mussels exposed to 5 μg/liter Ag for 6 months. Copper accumulation in the silver-exposed juveniles was significant only at 50 μg/liter Ag after 6 months, but at all test concentrations after 12 months. Adult mussels exposed to silver accumulated significant levels of both silver and copper, but at somewhat lower levels than juveniles.In the growth study, silver had no effect on laboratory reared mussels at the highest concentration of 10 μg/liter tested, whereas copper at 10 μg/liter did appear to affect growth as early as 4 months after the start of experimental exposure. Field-collected juvenile mussels did show inhibition in growth after 6 months' exposure to 25 and 50 μg/liter Ag, with some growth occurring after 12 months. Adults also showed inhibition in growth after 6 months but not at 12 months.Histopathological examination of mussels exposed to either 5 or 10 μg/liter of copper for 18 months showed changes in the digestive diverticula, gastrointestinal tract, reproductive tract and muscle tissues. These changes were more noticeable in mussels exposed to 5 μg/liter Cu than in those exposed to 10 μg/liter. Mussels exposed to silver for 21 months showed yellowish to black particulate deposition in the basement membrane and connective tissue of the various organs and tissues. Silver deposition increased with increasing test concentration.     

Polycyclic aromatic hydrocarbon (PAH) burden of mussels (Mytilus sp.) in different marine environments in relation with sediment PAH contamination, and bioavailability

Sediments and mussels (Mytilus edulis, Mytilus galloprovincialis) were sampled in different European coastal environments (Germany, France, Spain) and analysed for their polycyclic aromatic hydrocarbon (PAH) content by Gas Chromatography/Mass Spectrometry (GC-MS). Bioaccumulation factors of individual compounds from the sediment were calculated and discussed according to the compound solubility. The mussels showed different accumulation patterns according to the pollution source they were exposed to (dissolved fraction of PAHs, particulate fraction, petroleum present in the water column). The exposure source also depends on the geographical location of the mussels. In the Mediterranean Sea, the bivalves were mainly exposed to the dissolved fraction of PAHs, while in the Baltic Sea and in the Atlantic Ocean, the PAHs associated to the particles were significant sources.     

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.     

Stability constants of NaSO4−, MgSO4, MgF+, MgCl+ ion pairs at the ionic strength of seawater by potentiometry

The stability of the ion pair NaSO₄ was determined by measuring the change in sodium activity with medium composition at constant ionic strength, using a sodium-sensitive glass electrode. The stability constants of MgSO₄ and MgCl⁺ were determined indirectly from measurements of the stability of MgF⁺ in different media. All measurements were performed at 1 atm pressure, 25 ± 0.1 °C and 0.7 M formal ionic strength. The stability constants for NaSO₄^?, MgSO₄, MgF⁺ and MgCl⁺ are 1.8 ± 0.1, 6.3 ± 0.1, 22.9 ± 0.1 and 0.34 ± 0.02 M^?1, respectively.     

Uptake of palytoxin‐like compounds by shellfish fed Ostreopsis siamensis (Dinophyceae)

Abstract

Greenshell? mussels (Perna canaliculus Gmelin), scallops (Pecten novaezealandiae Reeve), and Pacific oysters (Crassostrea gigas Thunberg) were fed with a New Zealand strain of mass cultured Ostreopsis siamensis Schmidt (for 27 and 84 h and with 1.5 × 10⁶ or 8.6 × 10⁶ cells, respectively) under laboratory conditions. The microalgal cells contained 0.3 pg palytoxin equivalents cell^–1 (as determined by the haemolysis neutralisation assay (HNA) of Bignami (1993)) and extracts of these cells were toxic to mice after intraperitoneal injection. No palytoxin‐like material was detected either in the hepatopancreas or the muscle and roe of mussels fed O. siamensis. Oysters contained detectable amounts of toxin in hepatopancreas muscle, and roe while higher concentrations were present in the hepatopancreas of scallops. Extracts of control shellfish (tested biotoxin free and not fed O. siamensis) were toxic to mice, and there was no definitive evidence that feeding shellfish with O. siamensis at the levels employed in the present experiment increased the toxicity of shellfish tissue extracts to mice.     

Physico-chemical Speciation of Lead in South San Francisco Bay

The speciation of lead at a site in the South San Francisco Bay was determined using a combination of physical size fractionation and electrochemical analyses. The ‘ total dissolvable ’ Pb was 8·1 nM from analysis of an acidified unfiltered sample. The ‘ dissolved ’ Pb was equal to 0·20 nM (41 ng l⁻¹), only 2·5% of the ‘ total dissolvable ’ Pb. The difference yielded the ‘ particulate ’ Pb equal to 7·9 nM (1·6 μg l⁻¹). Results from crossflow ultrafiltration indicated that almost all (0·19 nM) of the dissolved Pb was ‘ in solution ’ [<10K nominal molecular weight (MW)] and that colloidal Pb (10K MW to 0·2 μm)accounted for onlyc. 1% of the dissolved Pb at this station. This small concentration (0·01 nM) of colloidal Pb may be attributed to the low amount of organic carbon associated with colloid size fraction as determined by dissolved organic carbon analyses.The chemical speciation of lead was determined in the dissolved sample and ultrafiltered sub-sample. Differential pulse anodic stripping voltammetry (DPASV) on a thin mercury film (TMF) rotating glassy carbon disk electrode (RGCDE) was used to distinguish the kinetically labile inorganic species (Pb′) from the Pb-chelated by organic ligands (PbL_i). Lead titration results were similar for both samples revealing that Pb′, PbL_iand excess unbound ligands were present primarily in the ultrafiltrate, rather than in the colloidal phase. The titration data can be interpreted as dissolved Pb being influenced by two classes of Pb-binding ligands. In the dissolved sample, the concentration of the stronger class of ligands was [L₁]=0·89±0·35 nM, with a conditional stability constant ofK^cond_L1,Pb′=3±1×10¹⁰M⁻¹. The weaker class was [L₂]=12·8±1·9 nM, withK^cond_L1,Pb′=4±1×10⁸ M⁻¹. The presence of these ligands, in excess of the dissolved Pb, resulted in [Pb′]=7±2 pM and [Pb²⁺]=0·3 pM (62 pg l⁻¹). While less than 2·4% of the ambient Pb was ‘ in solution ’, it existed chiefly in the form of organic complexes with [PbL₁]=0·15 nM and [PbL₂]=0·03 nM. More significantly, there were large concentrations of unchelated Pb-binding ligands, (L_i′), available to buffer the free Pb²⁺concentration in the event of perturbations in dissolved Pb.     

Some effects of copper on the veliger larvae of the mussel Mytilus edulis and the Scallop Pecten maximus (Mollusca, Bivalvia)

During 1983 and 1985 several batches of laboratory reared veliger larvae of Mytilus edulis and Pecten maximum here subjected to a rank of concentrations of added copper (CuCl₂) over a 15-day period. M. edulis larvae were less sensitive, measured both as mortality (15-day LC₅₀) of 400 μglitre⁻¹) and reduced growth, than P. maximus larvae (15-day LC₅₀ of 85μg litre⁻¹). Both species appeared less sensitive to Cu than other bivallve larvae previously studied. Veliger larvae of M. edulis are from 7 to 10 times more tolerant of Cu than juveniles or adults and this unexpected finding is discussed in relation to the recent literatures on Cu toxicity and accumulation in mussels.