Here in Southeast Alaska clams can have high Paralytic Shellfish
Poisoning at all times of the years. Dungeness Crabs, and snails that
drill into clams can also be inedible. Alexandrium SP. is our primary
culprit of the deadly saxitoxins. Research has shown the algae that cause
the "red tide" here in Southeat Alaska are not the dangerous ones. You
can never tell unless a test is done whither the clam you just dug is hot
or not. We have had mussels measured at 20,000 micrograms per 100 grams
of tissue. 80 mg/100gms is the accepted level. Geoduck research has shown
hot and cool clams right next to each other. Some species tend to hold
the toxins longer than others. Scott.
 
 -----Original Message-----
From: Conchologists of America List
Sent: Friday, May 22, 1998 10:28 AM
To: ScottW; [log in to unmask]
Subject: More on Sargasso Sea -Reply
 
There is no direct connection between sargassum drifts and red tide.
 About the only thing
the two phenomena have in common is that they both involve
 algae.  Sargassum is a macroscopic (visible to the unaided eye) brown
alga, or "seaweed".
The organisms responsible for red tide are microscopic, s
ingle-celled algae, most often of the genus Gymnodinium, though other
related genera are
sometimes involved.  The individual organisms measure less t
han 0.04 mm, and are normally present in sea water in small numbers,
doing no harm.  But
occasionally, for reasons not fully understood, they multipl
y rapidly, to the point where thousands of them may be present per
milliliter of sea water.
Since the organisms themselves contain a reddish pigment
, the water, when so many organisms are present, actually looks red.
 This is what is called
a "red tide".  In addition to the red pigment, these org
anisms contain a small amount of a protein that is violently toxic to
humans.  Bivalve
mollusks, because of the way they feed (filtering particulate
matter from the water), concentrate this toxin in their tissues, and
become dangerously
(sometimes lethally) poisonous to anyone who eats them.  The
harvesting of bivalves is prohibited during a red tide, and for a period
thereafter, which of
course is detrimental to the shellfish industry.  Fortu
nately, red tides are usually quite localized.  When people hear that
*shellfish* are
dangerous to eat, they stop buying not just bivalves, but also
snails, squid, lobster, crabs, shrimp, and even ordinary fish, though
these are actually safe
to eat; so these industries suffer as well.
 
Paul Monfils