Brigitte Berthet

Contribution to the ecotoxicological study of cadmium, lead, copper and zinc in the mussel Mytilus edulis

The understanding of natural fluctuations of metal concentrations in mussels used as bio-indicators is indispensable for a good assessment of the disturbances due to pollution. We have studied thoroughly the factors which condition bioaccumulation by using controlled populations of mussels, Mytilus edulis L., sampled monthly over more than two years (March 1982–May 1984) in the Bay of Bourgneuf, France. Seasonal changes in metal levels have been recognized, maximum values being observed in winter and early spring and minimum in later spring and summer. Depending on metal and size group, the ratios between these maximum and minimum values varied between 1.56 and 3.43. The fluctuations in soft-tissue weight appear to be the main explanatory factor of seasonal variations in metal concentrations in mussels. Fluctuations in metal levels related to size of mussels were observed. Except for cadmium in mussels with a mean dry weight of soft tissues >0.2 g, a slight decrease in metal concentrations was observed for growing individuals: the regression coefficient b was -0.10, -0.11, -0.13 and -0.27 for Cd, Cu, Zn and Pb, respectively. The metals examined were rather uniformly distributed among the different groups of organs (visceral mass, gills and palps, “remainder”) and, consequently, several analyses of metals in different organs do not provide much more information than one analysis on the whole soft tissues. It is concluded that fluctuations related to size or season are reflected by only moderate differences in the maximum and minimum concentrations of metals in the mussels, but that they are nevertheless sufficient to conceal low chronic or short-term pollution, except at those sites where the “normal” environmental conditions are well-documented.

Bioaccumulation, toxicity and physico-chemical speciation of silver in bivalve molluscs: ecotoxicological and health consequences

Abstract The toxicity and bioaccumulation of silver have been studied comparatively in the freshwater bivalve Dreissena polymorpha and in four marine species: the oyster Crassostrea gigas, the mussel Mytilus galloprovincialis, the scallop Chlamys varia and the clam Scrobicularia plana. In the freshwater and marine mussels, the silver absorption was very limited but M. galloprovincialis was more susceptible than D. polymorpha. The oysters and scallops were silver accumulators but the effect of the metal was much more noxious in the second species. These data have demonstrated that no direct relationships exist between the global concentration in soft tissues and the susceptibility of the different bivalves. Thus the physico-chemical forms of storage of silver (silver sulphide, metal-binding proteinic compounds) were determined in each species and related to the high variability of biological responses. The modes of exposure (through food or water) influenced the binding of silver with cytosolic compounds (in oysters) and its biological effects (in scallops). Changes in salinity had only a moderate effect on silver bioaccumulation in oysters, a fact which is interesting since pollutions due to this metal often affect estuarine and coastal areas. In the light of these data, the potential injuries due to silver pollution may be attributable: (1) to noxious effects on susceptible species with a resulting imbalance of biocoenosis structure; and (2) to the existence of silver accumulation with a risk of transfer to the food web. However, the knowledge of the chemical speciation of silver in organisms permit to predict the importance of this risk.

A marine mesocosm study on the environmental fate of silver nanoparticles and toxicity effects on two endobenthic species: The ragworm Hediste diversicolor and the bivalve mollusc Scrobicularia plana

Silver nanoparticles are widely used in a range of products and processes for their antibacterial properties, electrical and thermal conductivity. The fate and effects of Ag nanoparticles were examined in two endobenthic species (Scrobicularia plana, Hediste diversicolor), under environmentally realistic conditions in outdoor mesocosms exposed to Ag at 10 μg L(-1) in nanoparticulate (Ag NPs) or soluble salt (AgNO3) forms for 21 days. Labile Ag was determined in water and sediment by using diffusive gradient in thin films. Ag levels were equivalent in contaminated Ag NPs mesocosms to those contaminated with the soluble form. Bioaccumulation of Ag was observed for both species exposed to either Ag in the nanoparticulate or ionic forms. Concerning biomarker responses, both soluble and nanoparticulate Ag forms, induced defenses against oxidative stress, detoxification, apoptosis, genotoxicity and immunomodulation. Nevertheless, DNA damages measured by the comet assay in the digestive gland of S. plana, and Phenoloxidase and lysozyme activities in S. plana and H. diversicolor, respectively, were higher in the presence of Ag NPs compared to soluble Ag suggesting a specific nano effect.

A suitable model for the biomonitoring of trace metal bioavailabilities in estuarine sediments: the annelid polychaete Nereis diversicolor

The need to use biomonitors representative of the sedimentary compartment has been recognized, particularly in estuaries. Thus, trace metal contamination has been monitored in an infaunal polychaete worm Nereis diversicolor and sediments in the Seine estuary and comparatively in the relatively clean Authie estuary (French coast of the English Channel) over two years taking samples every three months at both sites. No correlations were shown between total metal (Ag, Cd, Cu, Pb, Zn) concentrations in raw sediments and ragworms. Because these worms are known to be good biomonitors of the bioavailabilities of sedimentary trace metals, it follows that total sediment metal concentrations have a poor predictive ecotoxicological value. Using a correction factor to minimize the influence of weight, it is possible to make a good estimation of the average metal concentrations in a population of worms at a given site, sampling only a limited number of specimens. Metallothioneins are often considered to be good biomarkers of the presence of significant availabilities of trace metals. Metallothionein-like proteins (MTLPs) are present in N. diversicolor, but there is no significant relationship between MTLPs and metal concentrations. This situation might result from the importance of metal-containing granules, both extra- and intracellular, in ragworms.

Biochemical, physiological and behavioural markers in the endobenthic bivalve Scrobicularia plana as tools for the assessment of estuarine sediment quality.

The aim of this study was to link the responses at different levels of biological organisation of the endobenthic bivalve Scrobicularia plana differentially exposed to anthropogenic pressure. Clams were collected in April 2008 from three estuaries along a pollution gradient (Goyen < Loire < Seine). Biomarkers of defence (metallothionein concentration and glutathione-S-transferase activity) were activated in the Loire and the Seine. Biomarkers of damage revealed neurotoxicity (decreased AChE activity) and impairment of digestive enzyme activities (cellulase or amylase) in these estuaries. The highest lactate dehydrogenase activity was registered in the Loire estuary, in parallel with enhanced levels of vanadium (a metal present in petroleum), likely as a consequence of a small oil spill that occurred one month before the sampling collection. Physiological biomarkers (energy reserves as glycogen, lipids and proteins, condition and gonado-somatic indices) showed a few intersite differences. However, the median size was significantly lower in clams exposed to direct (chemicals) or indirect (available food) effects in the most contaminated site. Burrowing behaviour was disturbed in clams from both of the Loire and Seine estuaries, a response probably due to physiological impairment rather than to avoidance of contaminated sediment. The activation of defence mechanisms towards metals (metallothionein) and other classes of contaminants (the biotransformation enzyme glutathione-S-transferase) do not ensure a total protection since a number of impairments were observed at the infra-organismal (AChE and digestive enzyme activities) and individual (burrowing behaviour) levels in relation to the degree of anthropogenic pressure. However, even in the most contaminated estuary (Seine), historical records do not show a consistent decrease of S. plana populations.

Intersite variations of a battery of biomarkers at different levels of biological organisation in the estuarine endobenthic worm Nereis diversicolor (Polychaeta, Nereididae)

The ragworm Nereis diversicolor has been proposed as a sentinel species for the assessment of estuarine sediment quality. The aim of this study was to test the responsiveness of the worms using a battery of biomarkers in specimens from a moderately contaminated site (Loire estuary, Fr.) and a comparatively cleaner site (Bay of Bourgneuf, Fr.) as a reference site. Ragworms were collected on 7 occasions from April 2008 to October 2009 for the determination of biochemical (GST, AChE, digestive enzymes), physiological (energy reserves (glycogen, lipids and proteins), relationship between length and weight), and behavioural (feeding and burrowing) biomarkers. The biomarker responses were tentatively interpreted in terms of the concept of cascading events potentially responsible for local depletion/extinction of populations submitted to chemical stress. Impairments of AChE and amylase activities, feeding rate, energy reserve concentrations (glycogen and lipids), and the relationship between length and weight showed up differences between the reference site and the Loire estuary despite the latter being far from the most contaminated estuary in France or internationally. However, no links could be established in the Loire estuary ragworms between effects at infra-individual and individual levels, nor with worm population density, even though a small oil spill had occurred in the Loire estuary only one month before the beginning of sampling.

Cd Distribution in the Tissues of Oysters (Crassostrea Gigas) Exposed Chronically In Situ

This study was designed to monitor the evolution of the nature of Cd-binding molecular compounds in oysters transplanted from a low-contaminated area to a highly Cd-polluted site. These compounds have been compared to those found in oysters from the low-contaminated site, used as control, and from the native molluscs of the polluted area. We have also studied the influence of the length of exposure, collecting oysters after transplantation having been going on for 1 or 3 months. We have compared the quantities of Cd bound to soluble or insoluble compounds. The Cd distribution among cytosolic compounds was analyzed by gel permeation. Four classes of Cd-binding molecular compounds were separated and their relative significance in metal fixation was found to differ among resident and transplanted oysters.

Integrated assessment of estuarine sediment quality based on a multi-biomarker approach in the bivalve Scrobicularia plana

The bivalve Scrobicularia plana has been proposed as a sentinel species for the assessment of estuarine sediment quality. The aim of this study was to test the responsiveness of a set of biomarkers in bivalves originating from a moderately contaminated site (Loire estuary, France) and a comparatively cleaner site (Bay of Bourgneuf, France) used as reference. Temporal fluctuations were examined in animals collected on eight occasions from March 2008 to October 2009 for the determination of biochemical (MTs, GST, AChE), physiological (energy reserves as glycogen and lipids, condition, hepato-somatic and gonado-somatic indices), and behavioural biomarkers (burrowing). Metals in clams were examined with the aim of understanding the variations in MT concentrations. The current findings indicate that among biochemical markers MTs must be used in a precautionary fashion, and comparison with a reference site remains indispensable together with an appreciation of any salinity effects. Clearer responses were obtained for GST activity which contributes to defence against organic compounds. However, any such defence was not sufficient to ensure total protection since a number of impairments were observed at the individual level (burrowing behaviour, condition index, gonado-somatic index). The integrated biomarker response (IBR) illustrated higher levels of stress in clams collected from the Loire estuary compared to those gathered from the reference site at most of the sampling periods. The interpretation of responses involved in the cascade of energetic events (from available food, digestive enzyme activities, energy reserves to condition and reproductive status) is complex but did reveal disturbances in the Loire estuary which is far from being the most contaminated estuary in France and over the world. However, no links can be established between effects at individual and supra-individual levels in organisms in the Loire estuary, even in the case of a small oil spill which occurred at the beginning of this study.

Etude expérimentale de la relation entre la forme physicochimique du zinc et sa disponibilité à l'égard de végétaux cultivés. Application à l'utilisation agricole de boues de stations d'épuration

SummaryIn order to appraise the relation between the physico-chemical forms of Zn and its availability to plants or water, we introduced various forms of this element in experimental systems according to whether it was associated with soil, mineral fertilizers or sewage sludges. These sludges were rich in organic matter and carbonates and one of them contained iron and aluminium oxides and hydroxides.The physico-chemical forms of Zn in soils and sludges were determined following a selective extraction procedure which showed that only a small amount of this metal was associated with the easily available phase. In accordance with these results, the exportsvia vegetables and leached waters were very low, regardless of the treatment.

Endobenthic Invertebrates as Reference Species

Endobenthic species living in close contact with sediment are particularly at risk in contaminated environments. Being relatively sedentary, they cannot avoid deteriorating sediment quality conditions. They are representative of different zoological groups that contribute greatly to ecosystem structure and functioning. Bioaccumulation studies give access to the lability of sediment-bound contaminants, whereas associated risks for biota can be revealed by using biomarkers. Endobenthic invertebrates feed at a low level of the trophic web, but as preys, they have a crucial role in the trophic transfer of contaminants and toxicity. Diverse species exhibit different tolerances to stress, thus providing useful indicators of the health status of communities. For standardized bioassays, numerous species are commercially available, but the use of local species may be more relevant for a precise identification of chemical risk in a local area.