General Information

Event name: US-00-013
Nature of the harmful event:
Water Discoloration , High Phyto concentration
Event directly affected:
Planktonic life , Shellfish
Toxicity detected: Yes
Associated syndrome:
Unexplained toxicity: No
Species implicated in toxin transmission (transvector): Local oyster beds.
Report the outcome of a monitoring programme: Yes (Virginia Chesapeake Bay Phytoplankton Monitoring program, which includes input from the Virginia Dep)
Event occurred before in this location: Yes (The extent of this bloom was not normal. Smaller, short lived blooms are more typical.)
Individuals to contact: MARSHALL, Harold G.

Location & Date

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Location: Latitude: , Longitude:
General location information: Potomac River and inlets and small bays along, Virginia.
HAB Area code(s): US-10
Additional location information: Southeastern US, northern border of Virginia. The bloom moved down the middle and lower regions of the Potomac River, with highest concentrations of cells within numerous creeks, small inlets and bays along the southern shoreline to the mouth of the river.
Bloom event dates (yyyy/mm/dd): Start: 2000-05-01, End: 2000-05-18
Quarantine levels dates (yyyy/mm/dd):
Additional date-related information: Over the period of the bloom: Temp. ranged from 16.6-27.6 C, Oxygen ranged from 6.3-13.8 ml/l, Salinity was 2.7-16.0 ppm, and secchi at 0.2-1.2 meters.


Causative organism known: Yes
Causative Species/Genus: Prorocentrum minimum (49,000,000 cells/L)
This species was dominant throughout the water column
Co-Ocurring Species/Genus: Cryptomonas spp. (20,000 cells/L)
Chlorophyll concentration, if known: µg/l
Additional bloom information: The bloom was the product of only the Prorocentrum species. Other flora in the water column contributed little in abundance or biomass.
Event-related bibliography:

Environmental Conditions

Weather: Turbidity (NTU): 0.2-1.2 Wind direction:
Stratified water: No Oxygen content (nL/L): 6.3-13.8 Wind velocity:
Temperature (°C): 16.6-27.6 Oxygen saturation %: Current Direction:
Sechhi disk (m): Salinity: 2.7-16. Current Velocity: 0
Nutrient information:
Temperature Range During Event: Max: 27 °C, Min: 16 °C
Salinity Range During Event: Max: 16, Min: 2
Bloom location in the water column:
In situ
Growth Comments
Additional Environmental information:

Toxin Assay Information

Species containing the toxin Toxin type Toxin details Max. concentration Assay type
Kit used: No Type of kit used:
Additional information:
Economic losses: Total losses considered high to oyster fisheries. Financial loss given in millions $, actual value unknown to this investigato.
Management decision:
Additional harmful effect information: Established oyster beds experienced extensive oyster deaths in association with extensive algal bloom. It is not known if these deaths were caused by toxins or other factors. Range of toxicity: 10 km