TEMPORAL AND SPATIAL VARIATION IN LEVELS OF ALKYLTINS IN MUSSEL TISSUES - A TOXICOLOGICAL INTERPRETATION OF FIELD DATA

This study presents results of mussel tissue tributyltin (TBT) analyses from four study areas; the Lynher River, Cornwall, UK; Sullom Voe oil terminal, Shetlands, UK; Langesundfjord, Norway; Hamilton Harbour, Bermuda. To illustrate temporal variations in TBT concentrations, mussels Mytilus edulis were sampled and analysed for alkyltins at 1-3 month intervals between 1987 and 1989 from the Lynher River. The results show an inter-annual variation in [TBT] of lower winter values and higher late-spring-early-summer values, consistent with probable inputs from seasonal recreational boating superimposed on a background of dockyard-shipping TBT inputs and seasonal water exchange variations. An overall decrease in TBT inputs from 1987 to 1989 was observed. For the remaining three study areas, the spatial variation in tissue TBT concentration was related to scope for growth (SFG), a measure of net energy available for growth and reproduction. For both Sullom Voe oil terminal and Langesundford, Norway, the measured TBT concentration in M. edulis from the field were below the TBT concentration shown to have threshold of effect on SFG in laboratory studies. In both cases, observed variations in SFG could be related to other toxicants such as aromatic hydrocarbons. In Hamilton Harbor both petroleum-derived toxicants and TBT were identified as the major toxic contaminants causing a reduction in SFG in Arca zebra. Toxicological interpretation of the contaminants and their effects on the components of SFG indicated that TBT accounted for 35% of the observed decline in SFG from the innermost harbour site and petroleum-derived toxicants, the remaining 65%. The overall results show that it is possible to use toxicological relationships between tissue TBT concentrations and a physiological stress indicator such as SFG to interpret the likely toxic effects of TBT in field populations of mussels.