Environmental cadmium and lead concentrations in the Bahia Blanca Estuary (Argentina). Potential toxic effects of Cd and Pb on crab larvae

The Bahia Blanca Estuary includes a large tidal plain with an area close to 1150 km2.Mud is predominant in its sediments, where a significant population of the crab Chasmagnathus granulata lives during the whole year.Mo reover, there are important urban and industrial discharges into this environment. Cd and Pb concentrations were determined in samples of water (for both dissolved and suspended particulate matter) and surface sediments (total and <63 μm fractions).Or ganic matter was analysed in the sediments, while temperature, salinity, pH and dissolved oxygen were measured in the estuarine water The metal concentrations determined in this study were: 1.47 ± 1.08 μg Cd g−1 and 14.68 ± 4.31 μg Pb g−1 in surface sediments; 2.21 ± 1.33 μg Cd g−1 and 25.70 ± 7.09 μg Pb g−1 in the <63 μm sediment fraction; 0.18 ± 0.11 μg Cd g−1 and below the analytical detection limit of Pb in suspended particulate matter. Furthermore, dissolved Cd and Pb were lower than the norms for marine and estuarine waters (2 μg dm−3 for Cd and 5 μg dm−3 for Pb, E.P.A.). Simultaneously, the effects of Cd and Pb were studied on recently hatched larvae of Ch. granulata, through 96-hour semi-static acute assays.Via bility was the criterion assessed in the assays.LC 50 (96 h) for Cd was 46.43 μg dm−3 (36.92 − 56.34 μg dm−3), whilst that for Pb was 1. 0 mg dm−3 (0.79 − 1.23 mg dm−3), which demonstrates that Cd is more toxic towards larvae.F inally, both LC50 values determined for Cd and Pb were higher than the corresponding metal concentrations measured in the Bah´ıa Blanca environment.