Brown Seaweed as an Indicator of Heavy Metals in Estuaries in South-West England

Abstract

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.

Metal Accumulation and Metallothionein Response in Fucus Spiralis

“…However, Cu concentrations in seawater in Poole Harbour do not exceed 3 µg/l [31]. For comparison, Zn, Fe, and Pb concentrations in F. vesiculosus from the Fal Estuary, Cornwall, were as much as an order of magnitude higher, with Cu two orders of magnitudes higher, compared to this study [56]. Owen, et al [9] did not report tissue concentrations as high in F. vesiculosus from the Fal Estuary; perhaps indicating a recovery of contamination levels, but the most polluted site studied was still approximately ten, five, and ten times higher respectively for Cu, Zn and Fe concentrations than in F. spiralis in this study.…”

“…Aside from low seawater concentrations, low accumulation of metals in seaweeds from Poole Harbour may be the product of low metal concentrations in the tips of fronds, with greater concentrations in the thallus [56]. It has been suggested to dissect the frond at a pre-determined distance from the distal end (10 cm for F. vesiculosus) to allow time for new growth to equilibrate with the environment [57,58].…”

Effects of Cadmium on Laminaria saccarina in Culture

“…Fuge and James (1974) further noted that older plant tissues contain higher concentrations, as has been shown in this study as well. Considering all these factors, and in agreement with Bryan and Hummerstone (1973), Laminaria plants should be useful as indicators of changes, if entire plants of the same age, or the same portions of such plants, are collected for analyses on the same site in the same season in subsequent years. A test of this method, taking into account the data in this study, remains to be carried out.…”

“…In these studies, growth measurements were conducted using zoospores, garnetophytes, and early sporophyte stages, whereas respiration, when tested, was measured in discs cut from adult, field-collected plants. These Laminaria studies, and analyses of the metal content of brown algae growing in polluted areas, especially species of Fucus (Bryan and Hummerstone, 1973;James, 1973,1974;Morris and Bale, 1975;Seeliger and Edwards, 1977) have established that uptake of heavy metals by brown algae is not regulated, reflects the concentration in the ambient seawater, and results in very high concentration factors, although the concentration factors are greater where the environmental concentration is lower.…”

Recent trends in research on heavy-metal contamination in the sea

“…Beau- Holliday & Liss, 1976;Rhine: Duinker & Nolting, 1978). Indeed, in some estuaries such as the Tamar, concentrations of Mn, Zn and Cu have been observed to peak at intermediate salinities, suggesting remobilization from the sediments or desorption from suspended particles (Bryan & Hummerstone, 1973;Morris et al, 1978). Redox conditions are particularly relevant to the remobilization of metals from sediments; reducing conditions tend to promote the solubilization of Mn and Fe, whereas oxidising conditions appear conducive not only to the release of Cd, Cu, Ni, Pb and Zn (Lu & Chen, 1977) but also to the microbiological methylation of Hg which is suspected to be the original source of methyl mercury in marine organisms {cf.…”