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Bioaccumulation of cadmium, copper, and zinc was examined in common ragworms Hediste diversicolor from control (Bay of Somme, Blackwater) and metal-rich (Seine estuary, Boulogne harbor, Restronguet Creek) sites in France and the United Kingdom. The degree of exposure in the field was assessed by considering both total concentrations in superficial sediment and the quantities of metals which may be released in vitro at different pH levels. Among the three contaminated sites, release of the three metals was not detectable in Boulogne harbor, in correlation with limited enhancement of the metal concentrations in the common ragworms from this site. Even at those sites where zinc could be released in vitro from the sediment, zinc concentrations were not enhanced in common ragworms, in agreement with previous findings indicating that the body content of this metal is regulated in H. diversicolor. At all the studied sites, bioaccumulated zinc was mainly in cytosolic form. The distribution of cadmium and copper varied according to the origin of the common rag-worms, the insoluble fraction increasing with the degree of contamination (cadmium in the Restronguet Creek, copper in the Seine estuary, and even more in Restronguet Creek). In the cytosolic fraction, metals were partly linked to cytosolic heat-stable thiolic compounds (CHSTC) with molecular masses (5-6 kDa and about 12 kDa) consistent with metallothionein-like proteins (MTLP). Metal-binding to MTLP varied with the degree of contamination and with the metal studied. In contrast to many invertebrates, the presence of metal-binding CHSTC (MM about 2 kDa) other than MTLP seems to be a peculiar feature of H. diversicolor.

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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.

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1988. Effets chimiques et cytologiqkees de la contamination experimentale de I'huitre Crasscsstsea gigas Thunberg par l'argent administre socas forme dissoute et par v~i e alimentaire. I. can. sci. haieket. aquat. 45: 1827-1 844.b'exposition de jeunes huitres (Crassostrea gigas Thunberg) A I'Ag dissous dans I'eau (20 pg.8-I) su incorpore A du phytoplancton (59'7 yg-g-I), provoque une bioaccumulation du metal qui atteint un pallier d&s ou avant le qasatorzieme jsur. ha contamination we cause aucune lesion cytologique, mais elle amplifie I'kmission des spermatomoi'des et dirninue le stockage du glycogene dans le tissu v6siculeux. Des Ag-proteines, naturellernent pr6-sentes chez les ternoins oO elles fixent 55 % du metal, complexent 30 % de I'Ag des huitres contamin6es. Le stockage du mktal dans les lysosomes des cellules des branchies et du syst6me digestif est tr6s faible ; la plus grande partie est irnmobilis6e sous forme de sulfasre dans les amoebocytes et dans les lames basales. Le pallier de concentration peut &re irnputk 3 Ifdimination continue des amoebocytes. Du point de vue 6cotoxicolsgique, I'immo~ilisation dtAg ssus forme de skelfure indique qu'uwe fraction importante du polleaant (envirbn 70 %) ne peut &re transfer6e aux niveaux trophiques superiecars.The exposure of young oysters (Crassostrea gigas Thunberg) to Ag introduced into seawater (20 yg. h-I) or linked to phytoplankton (59.7 pgg-') is responsible for a bioaccurnulation of this metal, the level of which reaches a plateau within 14 d. This contamination does not induce any cytological lesion, but it leads to an enhancement of the emission of spermatozoons and a decrease of the storage sf glycogen in the interstitial tissue. Ag-proteins (present by nature in oysters) account for 30% of the metal in contaminated oysters (55% in controls). The metal storage in the lysosomes of branchial and digestive cells is poor whereas the major part is sequestered as Agsulphide in amoebocytes and basement membranes. The steady state observed after 2 wk of exposure may be due to the continuous elimination of amoebocytes. From an ecotoxicslogical point of view, the transfer of Ag to higher trsphic levels will be limited, since an important fraction (70%) of the metal is sequestered in a very stable physicochernical form. 'agent donne lieu B des pollutions locales frkquentes. Au metal nature1 provenant du lessivage des sols s9ajoute une fraction like aux activitCs industrielles (combustion de dCchets urbains, conosions) et surtout B 19industrie phhstographisgue. E9extension gCographique de cette pollution est bien mise en evidence par Bryan et ak. (1983) qui montrent que, sw 59 estuaires de Grmde-B~hgme, 21 sont contaminks. Be plus, de l'Ag 1 10 rn est produit et rejet6 dans les milieux aquatiques au cours de plusieurs &apes du cycle du combustible nuclkaire. h s Ctudes expCrirnentales montrent que I'Ag est tres toxique pour Hes laves de divers HnvertCbr6s dona %es Molleasques (Amiad 1946 ; Calabrese et a&. 1979). En revanche, les individus ayant d6passt-5 B e sta...