Blooms of the planktonic alga Phaeocystis pouchetii in the continental coastal zones of the
North Sea have been observed to occur more and more frequently and intensively over the
past twenty years, probably as a result of nutrient enrichment from river discharge. The
peculiar physiology of this colony-forming flagellate strongly influences the structure and
function of the coastal ecosystem. It is a major nuisance alga mainly because it can lead to
the development of massive foam banks which accumulate near shore.