This book is a Thesis whose aim is to study the effect of organic matter enrichment produced by marine finfish farming and oil spills on the marine environment. This work is focused on elucidating the ecological consequences of the impact generated by this type of pollution, and on designing toxictity tests to evaluate pollution for southern European coasts. The present thesis is introduced with a chapter that discusses issues related with the assessment of benthic impact due to marine finfish farming in the Mediterranean, emphasising the usefulness of toxicity tests as a tool for assessing pollution produced by fish farming, as well as by other types of organic enrichment. The results and conclusions derived from this thesis should contribute to our knowledge in these fields of research.