Cadmium and lead in a trophic marine chain

Abstract

Heavy metals participate in complex biogeochemical cycles whose final destination (except on a geological scale)is the bottom of oceans and lakes. This implies that to reach the bottom the metals of the sediment have to travel through the water column. The main source of heavy metals in sea-water is particulate matter both air and water. Different organism can bioaccumulate heavy metals and eventually reach toxic levels. This happens when their normal levels are exceeded because of anthropic activities thus exposing to the human population who consume seafood to a potential danger. Metal concentration in seafood is determined by age, feeding habits, and by the trophic level to which the respective species belong to. Heavy metal transfer from one trophic level to a higher one in marine environments have been described already (McDonald and Sprague, 1988; Blomqvist et al., 1987). However, There is a lack of knowledge about heavy metals dynamics in relation to their accumulation in living organisms and their access to the marine environment of the Arauco Gulf. The present attempts to study the behaviour of metals in a benthonic-demersal trophic chain which originates in the organic matter of the sea bottom sediments where these metals, due to hypoxic conditions ("oxigen minimum")during almost all part of the year, may accumulate. This organic matter serves as nourishment to Pleuroncodes monodon ("squat lobster") which, in turn, is an important food source for Genypterus maculatus ("black ling"). Both these species are abundant in this area and are economically important as food supply for the population, both in their fresh and frozen forms.