Phytoplankton, or algae, are normal components of all aquatic environments, creating the base of both marine and freshwater food webs. When phytoplankton bloom in significant numbers and produce biotoxins, these events are termed harmful algal blooms or HABs.
HABs represent a present and growing threat to virtually all U.S. coastal waters, where their impacts range from devastating economic effects to public health risks to ecosystem alterations. Often referred to collectively as "red tides,” HABs are most often of concern because of the extremely potent toxins they produce. When HAB toxins accumulate in marine animals they lead to closures of commercial and recreational fisheries, mass mortalities of birds, fish, and marine mammals, and human illness or death in extreme cases.