General Information

Event name: US-92-004
Nature of the harmful event:
Seafood toxins
Event directly affected:
Toxicity detected: Yes (Approximate range: 500 g STXeq / 100 g. Muscular tissue.)
Associated syndrome: PSP
Unexplained toxicity: No
Species implicated in toxin transmission (transvector):
Report the outcome of a monitoring programme: Yes
Event occurred before in this location: Yes (High levels of paralytic shellfish toxins were first observed in Georges Bank shellfish in 1989. Toxin levels increased in 1990. Despite the absence of Alexandrium blooms for the past 2 years, toxin levels in surf clams still remain above the public health safety threshold.)
Individuals to contact: WHITE, Alan

Location & Date

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Location: Latitude: , Longitude:
General location information: Georges Bank (offshore)., Massachusetts.
HAB Area code(s): US-06
Additional location information:
Bloom event dates (yyyy/mm/dd):
Quarantine levels dates (yyyy/mm/dd):
Additional date-related information: Throughout the year.


Causative organism known: Yes
Causative Species/Genus: Alexandrium sp. ( cells/L)
Variety not yet detemined.
Co-Ocurring Species/Genus:
Chlorophyll concentration, if known: µg/l
Additional bloom information: Alexandrium fundyense and/or Alexandrium tamarense (Variety not yet detemined).
Event-related bibliography:

Environmental Conditions

Weather: Turbidity (NTU): Wind direction:
Stratified water: Yes 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: 12 °C, Min: 10 °C
Salinity Range During Event:
Bloom location in the water column:
Growth Comments The origin of the offshore toxicity and its relationship with inshore toxicity remain unknown.
Additional Environmental information: Georges Bank is an open ocean environment, 100-200 miles from the nearest land (Cape Cod). Much of the Georges Bank area is very shallow (10-15 m). The region is a rich fishing grounds for shellfish and finfish. Stratification of the waters overlying Geo

Toxin Assay Information

Species containing the toxin Toxin type Toxin details Max. concentration Assay type
Spisula solidissima Saxitoxins 100-200 Bioassay-Mouse
Spisula solidissima (muscular tissues) Saxitoxins 200-500 Bioassay-Mouse
Kit used: No Type of kit used:
Additional information: Surf clams (Spisula solidissima) on Georges Bank continued to retain paralytic shellfish toxins that were accumulated during May and June 1990.
Economic losses:
Management decision: The closure of Georges Bank to harvest of certain molluscan shellfish was continued throughout 1992.
Additional harmful effect information: No human deaths or illnesses occurred.