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(228) Exposition of three micro-algae species to different estuarine sediment elutriates: effects on growth, metal uptake and organic ligands concentration. Mucha, Ana1, Leal, M. Fernanda2, Vasconcelos, M. Teresa2, Bordalo, Adriano1, 1 2 ABSTRACT- Elutriate Sediment Toxicity Test (ESTT) provides a measure of the amount of a substance that is exchanged between the sediment and the aqueous phase during dredging and disposal process. This study had two complementary aims: (a) a comparison of the elutriates of two estuarine sediments (anaerobic muddy (A) and aerobic sandy (B)) in terms of toxicity and (b) a comparison of the response of three different micro-algae (Emiliania huxleyi (coccolithophore), Dunaliella minuta (green algae) and Phaeodactylum tricornutum (diatom)) to each elutriate. The chemical composition of the seawater (control), and elutriates before the algae inoculation, was characterised in terms of dissolved nutrients (NH4+, NO3-, NO2-, PO43-, Si), total dissolved metals (Zn, Cu, Pb, Cd, Cr, Ni, Co, Fe and Mn) and organic ligands (CL). After inoculation, the cell number was counted every 2 days. After 10 days of growth, cultures were filtered to determine the metal uptake by the algae and the CL in the solution. Elutriate A was toxic for P. tricornutum (growth inhibition) but stimulated the growth of E. huxleyi and D. minuta. Elutriate B displayed no toxicity in all cases, and fostered higher stimulation of the growth of all algae. Therefore, the P. tricornutum behaved differently from E. huxleyi and D. minuta in the presence of elutriate A, illustrating the influence of the sensitivity of the micro-algae on the results of the ESTT. It must be stressed the importance of the choice of the test species especially when management decisions are to be made. A detailed interpretation of these results will be based on the chemical composition of the culture media. Key words: algae, elutriates, metals, ligands |
