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The aim of the present study was to evaluate marine contamination and toxicity in sediment and pore water from the areas of Izmir Bay (Turkey) and Mytilene Harbor (Greece). The evaluation was performed in terms of selected toxic metals, polycyclic aromatic compounds (PAH) and toxicity to sea urchin (Paracentrotus lividus) early development and fertilization. Significantly higher levels of metals and total PAH were detected in Izmir vs. Mytilene sediment, and the highest contamination was detected in Izmir Bay innermost sites. Bioassays were carried out in P. lividus embryos and sperm, by evaluating developmental defects and changes in fertilization success by exposing sea urchin embryos or sperm to sediment/seawater suspensions. Whole sediment (WS) showed a higher toxicity of Izmir vs. Mytilene samples both in terms of developmental defects and of spermiotoxicity. Pore water (PW) and solid phase (SP) were separated by WS centrifugation and tested on embryos or sperm. The induction of developmental defects showed a significantly higher toxicity of WS compared to SP and, even more so, to PW. A significant decrease in fertilization success was observed following sperm suspension in SP from both Izmir and Mytilene sediment samples, whereas PW-exposed sperm failed to display any decrease of fertilization success vs. controls. The use of WS bioassays is suggested as a default procedure in sediment toxicity testing, especially in a topographic characterization of polluted sediments. © Published by Central Fisheries Research Institute (CFRI) Trabzon, Turkey. more...