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was recorded in Spain (63 cases), France (33 cases), Italy (38 cases), Switzerland (23 cases)
and Germany (19 cases) (Viviani et al., 1977, 1978; Lüthy, 1979). This incident in western
Europe was caused by mussels (Mytilus edulis) originating from Vigo and Pontevedra (Atlantic
coast of Spain) (Lüthy, 1979). During the last two decades PSP has been observed in temperate
and tropical areas throughout the world, with increasing frequency. It is not clear whether this
is a true increase, or it results from improvement in surveillance, detection and reporting
systems.
The introduction of toxic dinoflagellates into all seas of the world can be made through
their cysts in the ballast water of vessels collected during a red tide. Episodes of PSP caused
by red tides attributed to hypertrophication of terrestrial origin and to marine aquaculture in the
last ten years are reported. So, for example, the population of Shatin and Tai Po in Hong Kong's
coast has increased from 70,000 in 1973 to 600,000 in 1988, and an ultimate population by 1990
of more than 1 million is anticipated (Morton, 1989). The surface waters of the Tolo Harbour
system, polluted by these cities and from agricultural waters have experienced a progressive
increase in phytoplankton standing crop and in the incidences of red tides. The occurrence of
red tides as well as fish kills due to red tides, algal blooms and oxygen depletions in Tolo
Harbour have shown a progressive increase since 1979, and have become regular phenomena
in recent years (Morton, 1989).
Paralytic shellfish poisoning (PSP) from Protogonyaulax toxicity levels in shellfish
collected from Tolo Harbour have, on average, tripled from 1984 to 1987 (Morton, 1989). The
intensification of aquaculture has also influenced the quality of the water leading to an increase
of toxic phytoplanktonic blooms and of the appearance of cases of PSP (Mortensen, 1985; Eng
et al., 1989; Phillips and Tanabe, 1989). This has occurred both in the coastal waters of the
Atlantic and in countries of the Far East. In the Faroe Islands in 1984, the first proof was found
that a relationship exists between aquaculture pollution and red tides caused by Gonyaulax
excavata, which results in massive fish kills and cases of PSP in man after having eaten
mussels from the same area (Mortensen, 1985). Similar cases have occurred in the Far East
(Eng et al., 1989; Phillips and Tanabe, 1989). Management measures to mitigate deteriorating
coastal water quality and the adverse environmental impacts of aquaculture development are
now required as a matter of urgency.
7.2.1.4 PSP in the Mediterranean sea
In 1989-1990 there are the first reports of PSP in shellfish in north-western
Mediterranean. Routine toxicity testing of Venus verrucosa of Andalucian origin revealed rising
levels of PSP toxins during January 1989. Toxin levels in the clam Cytherea chione reached 200
µg equiv. saxitoxin/100 g meat in February and collecting of shellfish was forbidden. Plankton
samples taken along the coast between Malaga and Bahia de Algeciras just north of Gibraltar
(the northern shore of the Alboran sea) an area subject to continuous inflow of Atlantic waters,
revealed Gymnodinium catenatum in concentrations up to 3000 cells L -1 in mid February. No
other species were found (Bravo et al., 1990). A bloom of Alexandrium minutum, reaching
concentrations up to 28 x 10 6 cells L -1 , was observed in the harbour of S. Carles de la Rapita
(northwestern Mediterranean) on 4 th May 1989. During the following days, PSP toxicity was
detected in mussels exposed to harbour waters and in mussels from the neighbouring bay of
Els Alfacs, where extensive cultures of bivalves are located. In El Fangar, the other by of the
delta, A. minutum was recorded in lower concentrations and no toxicity was detected in
mussels. Shellfish extraction was stopped in the delta region and no human illnesses occurred
(Delgado et al., 1990).