Atmospheric deposition is an important pathway by which bioactive trace metals are delivered to the surface ocean. Although trace metals in the sea are normally present at low concentrations, they may have a considerable biological effect on the biota. Some trace metals, such as Fe, Co or Mo, may influence the productivity and species composition of phytoplankton, while others may have a toxic effect (e.g. Pb and Cu). These processes are in particular important in the Mediterranean, an oligotrophic basin where complex interactions among ocean stratification, nutrients availability, and radiation play a central role in regulating the ecosystem response to long-term occurring changes.