Waste Disposal in the Marine Environment. 1. Biological Availability of Heavy Metals to Marine Invertebrates

Anthropogenic wastes such as fly ash, drilling muds, dredged materials and sewage sludge often contain significant amounts of trace metals. Disposal of these materials in coastal or marine waters may result in metal contamination of bottom sediments. There exists considerable uncertainty about the ultimate availability of these metals to the marine fauna, either through direct uptake of desorbed trace elements by deposit-feeding and suspension-feeding benthic invertebrates, or through food-web biomagnification processes. The relative importance of these different pathways of metal transfer is still poorly understood. Field investigations augmented by laboratory studies have shown that the rate and degree of metal contamination by marine organisms is controlled by a number of interacting factors. Predictions of metal concentrations in marine organisms exposed to metal contaminated sediments are therefore difficult to make. This paper is a summary of results from recent field investigations and laboratory studies and will focus on the relative bioavailability of particulate-bound metals from a variety of man-induced sources. The relative importance of sediment organic content, grain size, salinity, redox potential, pH and level of contamination of the sediment will be discussed with respect to the availability of toxic metals to various marine organisms and in relation to recent investigations conducted by the authors.