Amphipod and sea urchin tests to assess the toxicity of Mediterranean sediments:: the case of Portman Bay

The sediment formed by the tailings of an abandoned mine, which discharged into Portman Bay, Murcia. SE-Spain. was tested to establish a possible gradient of heavy metals. The results were compared with tolerance limits of what was calculated from control sites. Whole sediment toxicity tests were performed on two amphipod species, Gammarus aequicauda and Microdeutopus gryllotalpa, while sediment-water interface and porewater toxicity tests were performed on three sea urchins species, Arbacia lixula, Paracentrotus lividus and Sphaerechinus granularis. The sensitivity of these marine organisms was evaluated by exposure tests using the reference substances: ammonium chloride (NH4Cl), cadmium chloride (CdCl2), potassium dichromate (K2Cr2O7), sodium dodecyl Sulfate (C12H25NaO4S) and zinc sulfate (ZuSO(4)). The concentration of heavy metals decreased along the pollution gradient. Amphipod 16 day acute toxicity tests clearly demonstrated the gradient of toxicity. The sediment-water interface tests conducted with sea urchins also pointed to a pollution gradient and were more sensitive than the tests involving amphipods.