Volume26/Number 1 I/November 1993 Marine Pollution Bulletin, Volume 26, No. I1, pp. 593-601. 1993. Printed in Great Britain. Cosmopolitan Biomonitors of Trace Metals 0025 326X/93 $6.00+0.00 © 1993 Pergamon Press Ltd PHILIP S. RAINBOW* and DAVID J. H. PHILLIPSt *School of Biological Sciences, Queen Mary & Westfield College, Mile End Road, London E1 4NS, UK racer Environmental, Howard Court, Manor Park, Daresbury, Nr. Runcorn, Cheshire WA 71S J, UK Phil Rainbow is a Reader in Marine Biology at Queen Mary & Westfield College, University of London. Dave Phillips is a Director of Acer Environmental, based at Daresbury in England. Both have extensive experience of biomonitoring worldwide, and are co-authors of the recent book entitled Biomonitoring of Trace Aquatic Contaminants. As employed here, the term biomonitors denotes those aquatic species which accumulate trace metals in their tissues and may therefore be analysed to monitor the bioavailability of such contaminants in riverine, estuarine or coastal ecosystems. This term is preferred to the alternatives (which include bio-indicators, sentinel organisms, and bioaccumulative indicators: see Goldberg et aL, 1978; Martin & Coughtrey, 1982; Hellawell, 1986), as it has been less mis-used and offers the least possibility of misinterpretation. The use of biomonitors to establish geographical and/or temporal variations in the bioavailable concen- trations of trace elements in coastal and estuarine waters is now well-established (Phillips, 1980; Bryan et al., 1980, 1985; Phillips & Rainbow, 1993). Bio- monitors provide time-integrated measures of the levels of available metals in their ambient waters, responding essentially only to the fraction of the total metal load present in the ecosystem that is of direct ecotoxico- logical relevance. In addition, biomonitors generally accumulate trace metals to high concentrations which may be relatively easily measured, with limited risk of sample contamination. Ideal biomonitors should also meet further selection criteria, these requiring that they should be sedentary; reasonably abundant at the sites of interest; easy to identify and sample; large enough for analysis; resistant to handling stress caused by laboratory studies or field transplantation; and tolerant of exposure to environmental variations in physico- chemical parameters (Butler et al., 1971; Phillips, 1980). Importantly, biomonitors of trace elements should preferably be strong net accumulators of the metals of concern and should not regulate the total concentration of an element in the body tissues when exposed to different metal bioavailabilities (Phillips & Rainbow, 1988; Rainbow et al., 1990). Responses to Sources of Metals Marine organisms take up trace metals from both solution and particulates. Uptake of elements from the latter source may involve the ingestion of suspended detritus or plankton in the case of suspension feeders such as mussels, oysters and barnacles, or that of deposited organic material in the case of sediment dwellers such as tellinid bivalves or polychaetes. Burrowing soft-bodied invertebrates may also take up metal released from sediment particles to interstitial water, at least where physico-chemical conditions in the sediment promote this. Talitrid amphipod crustaceans feed mainly on cast-up macroalgae in beach strand lines, the metal content of which will reflect the dissolved metal concentrations at the site of seaweed growth and at the site of deposition of the dead seaweed. Thus, the accumulated metal concentration of any single biomonitoring species will reflect metal availabilities in sources appropriate to that particular organism (e.g. see Bryan & Hummerstone, 1977; Ireland & Wootton, 1977; Phillips, 1979a). In order to obtain a total picture of metal bio- availabilities in a particular coastal or estuarine habitat, or indeed to compare the relative magnitudes of different metal sources in various locations, it is necessary to use a suite of biomonitors. Such a collection might include the following: • a macrophytic alga, responding essentially to dissolved metal sources only (see Phillips, 1993); • a suspension feeder, taking particles of a particular 593