General Information

Event name: GB-94-005
Nature of the harmful event:
Seafood toxins
Event directly affected:
Toxicity detected: Yes (Approximate range: 5,040 mu.)
Associated syndrome: PSP
Unexplained toxicity: No
Species implicated in toxin transmission (transvector):
Report the outcome of a monitoring programme: Yes (SOAFD Monitoring Programme.)
Event occurred before in this location: Yes (Regular occurrence since 1990.)
Individuals to contact: MACDONALD, Elspeth , HOWARD, Godfrey

Location & Date

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Location: Latitude: , Longitude:
General location information: , Orkney Islands.
HAB Area code(s): GB-20
Additional location information:
Bloom event dates (yyyy/mm/dd):
Quarantine levels dates (yyyy/mm/dd):
Additional date-related information: Early May - September. Six closure orders were enforced beginning on 21st May and finally lifted on 17th September.


Causative organism known: Yes
Causative Species/Genus: Alexandrium sp. (< 1,000 cells/L)
Alexandrium cf. Tamarense. Waulkmill Bay
Co-Ocurring Species/Genus:
Chlorophyll concentration, if known: µg/l
Additional bloom information:
Event-related bibliography:

Environmental Conditions

Weather: Summer weather was generally cool and wet. Turbidity (NTU): Wind direction:
Stratified water: No Oxygen content (nL/L): Wind velocity:
Temperature (°C): Oxygen saturation %: Current Direction:
Sechhi disk (m): Salinity: Current Velocity: 0
Nutrient information:
Temperature Range During Event: Max: °C, Min: °C
Salinity Range During Event:
Bloom location in the water column:
In situ
Growth Comments There is a small population of Alexandrium cysts in parts of Scapa Flow, so in some cases, toxicity could be caused by in-situ populations.
Additional Environmental information: No detailed information.

Toxin Assay Information

Species containing the toxin Toxin type Toxin details Max. concentration Assay type
Mytilus edulis Saxitoxins STX eq 658 ug/100g Bioassay-Mouse
Kit used: Type of kit used:
Additional information: PSP toxins detected in pectinids, mussels and razor fish from many sites in the area. Maximum toxicity (5,040 mu/658 ug/100g) was recorded in early June and although levels then declined, they did not drop below 400 mu until early September.
Economic losses:
Management decision: Six closure orders were enforced beginning on 21st May and finally lifted on 17th September.
Additional harmful effect information: PSP toxins were also detected in brown crab and lobsters but were found to be mainly < 400 mu. Velvel crabs had toxin levels up to 1924 mu. No action necessary, as fisherman imposed a voluntary closed season.
Updated at 09:59 on 9 Oct 2020