Among the causes suggested for the enhancement of Harmful Algal Blooms (HABs) are the important pool of discharged nutrients in the coastal waters and/or the significant changes in nutrient ratios induced by antrophogenic activities. The increase of HABs events that is occurring worldwide has also involved the NW Mediterranean, where there have been recorded numerous dinoflagellate blooms in the last 10 years. The Mediterranean physical-chemical characteristics make bloom occurrences apparently improbable. This traditional statement comes from extrapolating open sea characteristics to near-shore waters where bloom events actually occur and in addition have more repercussions. The NW Mediterranean supports a very high human population (100 habitants/m of coastline in some regions); therefore, near-shore waters are very much subjected to antrophogenic consequences. We present an extensive study of the stoichiometry of dissolved inorganic nutrients along 400 Km of a very much humanised coast (the NE Spanish coast). A general shift in nutrient ratios towards silicate limitation is evident and its implications in dinoflagellate bloom events with the interaction of other factors are discussed.