MAP Technical Reports Series No. 106 UNEP

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The main question was the source of domoic acid. It was originally discovered some
30 years ago in red alga Chondria armata in Japan (Daigo, 1959) and later identified in a
Mediterranean species Alsidium corallinum of the family of Rhodomelaceae (Impellizeri et al.,
1975).
7.3.5 Gymnodinium spp. blooms: Neurotoxic Shellfish Poisoning (NSP) and respiratory
irritation
All red tides reported in Florida are associated with mass mortality in marine animals.
Health problems caused by consumption of neurotoxin infested shellfish (NSP) and by inhalation
of the windsprayed cells were evidenced (Alam et al., 1975; Steidinger and Baden, 1984; Pierce,
1986).
7.3.5.1 NSP producing or potentially toxic dinoflagellates
The red tide-forming dinoflagellate, Ptychodiscus brevis (= Gymnodinium breve), is
one of the most notorius species for its mass fish kills and destruction of other marine life along
the coast of Florida. Resting cysts of P. breve are not present in sediment-water interface. The
motile form of P. brevis produces several neurotoxins, collectively called brevetoxins (or P.
brevis toxins). These accumulate in filter-feeding shellfish (oysters, clams) causing neurotoxic
shellfish poisoning (NSP) when consumed. An atoxic strain of G. breve was found in the Inland
sea, Japan (Okaichi, 1979). P. brevis appears to be not only restricted to the gulf of Mexico, the
east coast of Florida and North Carolina coast (Pierce, 1987), but in reports of some blooms
from northern Spain, Japan (Steidinger, 1983) and the eastern Mediterranean coast (Steidinger,
1983; Pagou and Ignatiades, 1990).
7.3.5.2 Chemistry of NSP components
P. brevis neurotoxin consisted of an eleven-number heterocyclic oxygen containing
fused ring system culminating in an unsaturated lactone at one end and an unsaturated aldehyde
at the other, designated brevetoxin-B (BTX-B) (Alam et al., 1975). Other brevetoxins were
characterized too (Chou and Shimizu, 1982; Nakanishi, 1985; Shimizu, 1987). Figure 26
illustrates the structures of brevetoxins according their nomenclature in the PbTX series
(Ptychodiscus brevis toxins) and two structural backbones a and b (Poli et al., 1986; Baden,
1988).
7.3.5.3 Brevetoxin compromised seafoods
The major seafoods containing brevetoxins are shellfish (Cummins et al., 1971). There
is little qualitative data on rates of accumulation and depuration of brevetoxins in bivalves.
Oysters accumulate the toxins in less than 4 hr in the presence of 5000 cells/ml, and depurate
(60%) of the accumulated toxin in 36 hr (Cummins and Stevens, 1970). Potency of depuration
is species-specific and highly variable, even under controlled laboratory conditions (Ray and
Aldrich, 1965). So commercial bivalves are generally safe to eat 1-2 month after the termination
of any single bloom episode. Canning cannot be a way for decreasing NSP concentration in
bivalves. The fishing industry also suffers due to adverse publicity concerning dead fish washed
ashore. The fish usually start dying when P. brevis counts reach the 250,000 cells/litre range.
7.3.5.4 Methods of analysis for NSP
Toxicity of contaminated shellfish is determined by the mouse bioassay, which
evaluates the cumulative effects rather than determining concentrations of individual toxins.