Arch. Environ. Contam. Toxicol. 26, 466--472(1994) ARCHIVES OF I~nvironmental Contamination n d Toxicology © 1994 Sprmger-Verlag New York Inc. A Comparison Between Particulate (Elemental) Zinc and Soluble Zinc (ZnCI2) Uptake and Effects in the Mussel, Mytilus edulis F. J. Burbidge 1, D. J. Macey l, J. Webb 2, V. Talbot 3 School of Biological and Environmental Sciences, Murdoch University, Murdoch, Western Australia 6150, Australia 2 School of Mathematical and Physical Sciences, Murdoch University, Murdoch, Western Australia 6150, Australia 3 60 Vincent Street, Nedlands, Western Australia 6009, Australia Received: 3 June 1993/Revised:6 November 1993 Abstract. The uptake of particulate (elemental) and soluble (ZnC12) zinc was compared in whole animals and individual organs in the mussel Mytilus edulis. Analysis of seawater showed that the addition of particulate zinc resulted in a maxi- mum concentration of 0.7 p~g/g dissolved zinc being present in the aquaria. Mussels exposed to either form of zinc at 10 Ixg/g accumulated it readily, although considerable mortality was experienced after 14 days. After loading with particulate zinc, depuration for 48 h significantly lowered (p < 0.001) the con- centration of zinc in whole mussels. Mussels loaded at 2 Ixg/g showed a similar pattern of accumulation to those exposed at 10 p~g/g, although with a lower mortality. Greater whole body concentrations were obtained with particulate zinc than with soluble zinc. On an organ basis, the kidney, gill, hepatopan- creas, and mantle were the major sites of accumulation follow- ing both soluble and particulate zinc loading, although gener- ally the levels were lower with particulate loading, indicating the possible presence of two different uptake pathways. The flesh condition index of mussels subjected to 10 ~g/g particu- late zinc declined compared to the control animals. Degenera- tion of the digestive tubules and the stomach was visible in zinc-loaded mussels while no such tissue damage was seen in control animals. Tissue damage, as indicated by the presence of large quantities of lipofuschin, occurred in the hepatopancreas and gonads of particulate zinc-loaded mussels. The results indi- cate that soluble zinc is both absorbed and taken up by the tissues far more readily than is particulate zinc, and these re- suits may be of significance with regard to zinc loading in the mussel Mytilus edulis. Many metals have become more abundant in the marine envi- ronment over recent times. A good example is zinc, the main source of which is from industries using processes such as metal stripping, galvanizing, or synthetic fiber production Correspondence to: D. J. Macey (Bryan 1971). Mytilus edulis and other bivalve molluscs have been recognised as particularly useful bio-indicators for metals such as zinc and have been used in worldwide pollution moni- toring programmes (Goldberg 1975; Goldberg et al. 1978). A classical case of zinc pollution occurred in the Derwent River estuary in Tasmania, Australia where both mussels and oysters growing in the estuary were found to have excessive levels of zinc in their tissues (Thrower and Eustace 1973; Cooper et al. 1982). In this case, while the plume of pollution was not di- rectly lethal, it did result in zinc concentrations in oysters that were so high that consumption by humans was emetic (Thrower and Eustace 1973). In seawater, zinc exists in three main forms, ionic, particu- late and chelated (Pentreath 1973). The soluble fraction exists predominantly as Zn 2÷, with a small amount present as ZnOH + (Myint and Tyler 1982). Up to 40% of the zinc is present in a particulate form (Pentreath 1973) and this, combined with the ability of M. edulis to filter fine particles (Lucas et al. 1987), suggests that ingestion is the most likely pathway of zinc uptake in mussels. Indeed, in the natural environment, food may be a more important source of zinc than seawater (Bryan 1971; Myint and Tyler 1982) with zinc being accumulated via the ingestion of phytoplankton (Phillips 1977; Amiard et al. 1986). A considerable body of work has been undertaken on zinc in Mytilus edulis. These studies include the effects of both envi- ronmental and biotic factors; uptake and loss of zinc from the tissues; the necessity of depuration; and the effects of other metals on the uptake and levels of zinc in the mussel (Keckes et al. 1969; Pentreath 1973; Phillips 1976; Boyden 1977; Gold- berg et al. 1978; George and Pirie 1980; Lobel et al. 1991). However, the majority of this work has used soluble, rather than particulate zinc and has focused on the mussel's ability to act as a long-term bio-indicator of general pollutants rather than a short-term monitor of single toxic events. More knowledge is required on the short-term response of the mussel to a variety of pollutants. Since zinc occurs both in soluble and particulate forms in the environment and mussels are known to accumulate metals in a particulate form (Bootsma et al. 1990), knowledge of the accumulation strategy for each form and the maximum levels of uptake for the particulate and