Donald F. Boesch, Donald A. Anderson, Rita A. Horner, Sandra
E. Shumway,Patricia A. Tester and Terry E. Whitledge. 1997. Harmful
Algal Blooms in Coastal Waters: Options for Prevention, Control
and Mitigation. NOAA Coastal Ocean Program, Decision Analysis
Series No. 10, Special Joint Report with the National Fish and
Wildlife Foundation, February 1997.
Site developer's note: genus and
species names of algae are indicated
in red, rather than standard underlining (not a webpage option
unless a link...) or italics, in order to make the names easier
to find and read.
Amnesic Shellfish Poisoning
Domoic acid has been detected in finfish and shellfish resources
on both the east and west coasts.. This neurotoxin, produced by
diatoms in the genus Pseudo-nitzschia,
may cause permanent short-term memory loss in victims, hence the
name amnesic shellfish poisoning (ASP). Another term often used
for this syndrome is domoic acid poisoning (DAP) because amnesia
is not always present and there have been no confirmed cases of
ASP in humans in the U.S.
Toxic Pseudo-nitzschia species are present in the northeast
and Gulf of Mexico and low levels of domoic acid have been detected
in shellfish on the east coast, but not at levels that necessitate
quarantine. On the west coast, however, domoic acid poisoning
has been a serious problem affecting razor clams and Dungeness
crabs in California, Oregon, and Washington.
The west coast has two different environments to consider in
terms of harmful algal bloom development. The Pacific Ocean coast
is associated with the upwelling events in late summer and fall.
On the other hand, inland waters of Puget Sound and fjords and
inlets of Alaska are enclosed areas with restricted water exchange.
Domoic acid production has been confirmed for three species
of Pseudo-nitzschia on the west coast:
P. australis, P. multiseries, and P. pungens.
Domoic acid poisoning first became a noticeable problem in 1991
when pelicans and cormorants in Monterey Bay (California) died
or suffered from unusual neurological symptoms similar to ASP.
Many tons of anchovy catches were recalled or diverted following
this episode. That same year, domoic acid was identified in razor
clams and Dungeness crabs on the Oregon and Washington coasts.
Since 1991, Pseudo-nitzschia spp. and domoic acid have recurred
in Monterey Bay, but relatively low cell numbers and concentrations.
Blooms are common in late summer and fall when the upwelling season
has ended, sea surface temperatures are warmer, thermal stratification
is evident, and concentrations of inorganic nutrients are low.
On the Washington coast razor clams on some beaches continue to
contain low levels of domoic acid, but the source in not known.
Meanwhile a bloom of mixed Pseudo-nitzschia species occurred in
Hood Canal (an arm of Puget Sound) in November-December 1994,
resulting in toxin levels of about 10 ug/g in mussels and 14 ug/g
in phytoplankton (Horner et al. 1996). Closure limits are 20 ug/g.
In western Washington, the economic impact for the 1991 domoic
acid event was estimated to be between $15 and 20 million based
on lost tourist visits (at $25 per digger trip); lost or delayed
retail sales and lower prices of oysters that were never toxic
but were avoided by confused consumers (halo effect), lost employment,
bankruptcies of local businesses, potential adverse health effects
(there were no confirmed illnesses due to domoic acid), and costs
to the state health department for increased testing.
To report problems or provide comments,
Andrew Kane (Aquatic Pathobiology Center) at:email@example.com
Dan Jacobs (Maryland Sea Grant)
UNIVERSITY OF MARYLAND
College of Ag & Natural Resources
Department of Veterinary Medicine
Aquatic Pathobiology Center