Concentrations of copper, zinc, lead, manganese and iron in the brown seaweed Fucus vesiculosus have been measured in samples collected over its range of distribution in four estuaries having different degrees of metal contamination. Factors controlling the concentrations in the weed have been studied and include the concentrations of metals in the water, seasonal changes, the position of the weed in the intertidal zone and the particular portion of the plant which is analysed. It is concluded that analysis of the weed gives a reasonable indication of average conditions in the water at points along an estuary and provides a method of making comparisons with the same estuary in subsequent years or with other estuaries.
I N T R O D U C T I O NIn the brown seaweed Fucus vesiculosus, the combined results of Black & Mitchell (1952), Young & Langille (1958) and Gutnecht (1965) have suggested that the concentration of zinc changes with that in the sea water. This was confirmed experimentally for zinc, copper and lead in Laminaria digitata, another brown weed, by Bryan (1969Bryan ( ,1971, although the relationship is not one of direct proportionality since at higher metal concentrations the concentration factor, relating the level in the weed to that in the water, is reduced. However, the weed would still be expected to reflect the average availability of metals in the water and, since concentration factors greater than 1000 to 1 are generally found, this property can be used for practical purposes.Fucoid seaweeds from the intertidal zone have been used as indicators of heavy metals in inshore waters around the British Isles by Preston et al. (1972) and in the Bristol Channel by Nickless, Stenner & Terrille (1972). It seems to be a reasonable technique, although one which it might be possible to refine by taking into account some of the factors which affect the relationship between metals in the seaweed and in the water. On open shores this relationship may be influenced by factors such as the time of year and the level of the weed in the intertidal zone, but, in estuaries, additional factors such as the variable salinity and the presence of high concentrations of particulate material may need to be considered. This paper compares the concentrations of heavy metals in Fucus vesiculosus from four estuaries in south-west England -the Tamar, the Restronguet Creek branch of the Fal, the Dart and the Camel. These drain parts of the mineralized zone which extends across Cornwall and into West Devon and differ markedly in the degree to which they are contaminated with metals such as zinc and copper.