Metals in the bivalve molluscs scrobicularia plana (da costa) and cerastoderma edule (L.) and associated surface sediment from oum er rbia estuary (Moroccan Atlantic coast)

Abstract

Concentrations of seven metals (Cd, Cu, Fe, Mn, Ni, Pb and Zn) were measured over a two‐year period in sediments and in tissues of bivalves Scrobicularia plana and Cerastoderma edule from a predominantly arid estuary (Oum er Rbia) on the Moroccan Atlantic coast. Metals mainly originated from run‐off from the surrounding agricultural lands and the urban waste‐waters of Azemmour city which are directly discharged into the lower estuary. Seasonal variations in metals were principally governed by certain hydrological parameters and the reproductive activity of the molluscs. Given the relatively high levels of metals in the sedimentary habitat of 5. plana and C. edule, estuarine sediments are likely to be the main source of metals to these organisms, either directly, or indirectly following desorption. Metal bioavailability in the Oum er Rbia is put into context with baseline values and highly contaminated estuarine sites in Europe, based on data for the same bivalve species.