Emmanuelle Rozuel

Metal concentrations in sediment and Nereis diversicolor in two Moroccan lagoons : Khnifiss and Oualidia

Metal concentrations were measured monthly during an annual cycle (December 2004 to January 2006) in the tissues of Nereis diversicolor ragworms and sediment from two Moroccan Atlantic coastal lagoons: Oualidia in the north, situated in a highly industrialised urban area and Khnifiss in the south, far from anthropogenic influences. Relatively high levels of Zn, Ag and Cd were found in the sediment of Oualidia lagoon, while Ni concentrations were shown to be high at Khnifiss. The significant metal levels at Oualidia are a result of industrial and urban discharges, coupled with discharges from adjacent phosphate ore processing plants. Trace metal concentrations in worms vary according to season; they are usually high in winter and spring, in relation to the animals reproductive cycle. Comparing the two lagoons, trace metal levels appear to be higher in worms from Khnifiss lagoon, suggesting a higher bioavailability of these elements in a relatively pristine area.

Retrospective study of metal contamination time trends in the French part of the Bay of Biscay

Two cores were sampled in the Bay of Biscay: one a few miles off the Gironde estuary (pointe de la Coubre), the other near the Spanish border (Capbreton canyon) to study past variations in sediment contamination. Radiochronology (210Pb, 137Cs) and total metal determinations by ICP-MS allowed the study of time trends for metal concentrations in sediment. Off the Gironde, during the time interval recorded by the core (1958–1999), all metal concentrations remained less than OSPAR background values. Some variations occurred along the Cd and Zn profiles, which may correspond to a very attenuated signal from the Gironde outputs. This suggests that this area was not submitted to any significant anthropogenic input of metals between 1958 and 1999. In the canyon of Capbreton, the undisturbed part of the core recorded the influence of surface deposition between 1977 and 1999. From as early as 1977 high lead and mercury concentrations were noticed. Mercury concentrations increased until 1992, then decreased until 1999. This marks a drop of inputs in 1992, but the final concentration remained elevated. Lead had important concentrations (more than twice the OSPAR reference) all along the core and began to decrease only in the upper level of the unmixed layer. This shows a late (near 1998) drop of lead inputs. Other metals (Cd, Cu, Zn, Ni, Cr) stayed at a much lower level: less than the OSPAR reference for Cu, Cr and Ni or not far from the OSPAR reference for Cd and Zn.

Trace metal concentrations in the muscle of seven marine species: Comparison between the Gulf of Lions (North-West Mediterranean Sea) and the Bay of Biscay (North-East Atlantic Ocean)

Concentrations of 6 trace metals (Ag, Cd, Cu, Ni, Pb, Zn) in the muscle of 2 sharks (Galeus melastomus and Scyliorhinus canicula), 4 teleosts (Helicolenus dactylopterus, Lepidorhombus boscii, Micromesistius poutassou and Phycis blennoides) and 1 crustacean (Nephrops norvegicus) were compared between the Bay of Biscay (Atlantic Ocean) and the Gulf of Lions (Mediterranean Sea). Although average concentrations and the trace element pollution index were generally higher in the Gulf of Lions, significant differences between the two ecosystems were only found for Zn for Helicolenus dactylopterus, and for Ag and Cu for the crustacean N. norvegicus. Moreover, some relationships between trophic level or size and metal concentrations were found for these two species. The absence of clear pattern may result from the blurring effect of contamination and excretion that may act differentially for all species and all elements.