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INTRODUCTIONIt has been known for a long time that the soft tissues of molluscs contain relatively high concentrations of certain trace elements—mainly transition metals (see, for example, Vinogradov, 1953; Bowen, 1966). However, with the exception of the work by Brooks & Rumsby (1965) on the occurrence of 12 elements in 3 New Zealand bivalves, most of the investigations have concerned the distribution of only one or two elements. This has prevented a study being made of possible interelement correlations. The present work was carried out in an endeavour to determine the usual levels of several minor elements in a variety of molluscs from the Irish Sea and to seek evidence for such correlations.

A study has been made of the seasonal variation of the free and combined amino acids at a station in the southern Irish Sea. The principal amino acids found were alanine, serine, glycine, threonine and valine. Acidic amino acids were generally present at lower levels and basic amino acids were usually below the detection limit. The variations observed for the free amino acids were small compared with those of the combined acids.

Many metallic elements are concentrated by marine animals to levels far in excess of their concentrations in sea water itself. This concentration extends not only to those elements which are known to have biochemical functions, but also to others which have no established biological role (e.g. cadmium and lead). Little is known about the mechanisms by which trace elements are concentrated, or about the manner in which they are held in the tissues. As a preliminary to the investigation of concentration mechanisms, reliable data are required concerning the distribution of the elements in a variety of marine animals.

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