The various chemical forms of 74As accumulated from either water or food by the marine food chain [Fucus spiralis (L.) ~ Littorina littoralis (L.) ~ Nucella Iapillus] have been separated and characterized. Arsenic components were separated by differential extraction followed by high-voltage paper electrophoresis/paper chromatography of the water-soluble fraction and thin-layer chromatography of the lipid-soluble fraction. The algae assimilates arsenic mainly (60%) as one lipidsoluble compound with Rf = 0.18, and 12 water-soluble organo-arsenic compounds as minor components. On the other hand, the snails, whether labelled from water or food, produce predominantly one major watersoluble organo-arsenic compound with Rf = 0.66. This water-soluble arsenic compound was produced by the snails and not by intestinal microbes. Timecourse studies on the relative proportions of labelled arsenic compounds in algal tissue indicate a transition from arsenate through water-soluble organo-arsenic components to a lipid-soluble arsenic compound. The water-soluble organo-arsenic compounds in the food chain studied were different from those previously found or proposed in marine organisms. et al., 1978). Lunde (1972a) and Penrose (1975) have shown that arsenate is converted to an organic form by brown trout when supplied via the digestive tract, but is not metabolised when injected into the fish or added to its surrounding medium. They concluded that microbes of the fish's gut were responsible for converting the arsenate. Similarly, Wrench et al. (1979), in their study of arsenic metabolism in a marine food chain (phytoplankton -zooplankton -shrimp), found that the shrimp accumulated arsenate from water as arsenite, whereas, algae and food-labelled consumers incorporated organo-arsenic. These findings are in agreement with the suggestion by Lunde (1972b) that organo-arsenic in marine organisms is derived from primary producers.
The present study extends previous work on arsenic accumulation in a marine food chain (see Klumpp, 1980 a, b) by examining the chemical characteristics of arsenic at each trophic level. The source of organoarsenic for higher trophic levels and the mechanism by which it is formed have also been investigated. Identification of arsenic compounds was not a priority of this study although synthetic arsenic compounds were compared with organo-arsenic extracted from marine organisms.