HABs and Biotoxins: West Coast HABs - Alexandrium
spp. are most notable because some
members of this genus produce the PSP suite of toxins and are responsible
for most PSP outbreaks in cool temperate ocean waters along the west
and east coasts of North America. PSP is not unique to only cool temperate
waters, it also occurs in warm tropical areas. In these warmer waters
the responsible organism is most notably Pyrodinium bahamense
. Unlike the diatoms, dinoflagellates (as their
name implies) have at least one flagella or "tail" that permits
them to move
through the water. Because of this property, dinoflagellates
move up and down through the water column, usually coming near the surface
during the daylight hours and moving down during the night. In some
species of armored dinoflagellates, this flagella can be wound around
the organism and lay in the girdle crease that encircles the cell.
The identification of toxic Alexandrium from other members of
the genus and other dinoflagellates can be difficult and requires some
degree of skill and training. These organisms are called "armored"
dinoflagellates because the cell is covered by 'thecal' plates. These
plates are used to distinguish one Alexandrium species from another.
To further complicate identification and observation, particularly in
regard to possible bloom of this HAB, the cell can shed the armor and
also go into a 'cyst forming stage' that can be morphologically difficult
to see and identify. Along the west coast of North America, the most
common culprit involved in PSP outbreaks is Alexandrium catenella.
Along the eastern coasts of Canada and the U.S., A. tamarense
has been implicated in PSP events. However, A. tamarense has
also been observed in waters of the west coast of Canada (British Columbia)
and in northern Puget Sound in Washington State.