General Information

Event name: US-19-021
Nature of the harmful event:
High Phyto concentration , Mass mortalities
Event directly affected:
Natural Fish
Toxicity detected: No
Associated syndrome: OTHER
Unexplained toxicity: No
Species implicated in toxin transmission (transvector):
Report the outcome of a monitoring programme: Yes (Environmental monitoring programs of Maryland Department of Natural Resources, Virginia Department of Health, and Maryland Department of Environment)
Event occurred before in this location: No
Individuals to contact: WOLNY, Jennifer , EGERTON, Todd

Location & Date

[View larger map]
Location: Latitude: , Longitude:
General location information: Potomac River,
HAB Area code(s): US-10
Additional location information: 38.3625N -76.9906W to 38.1439N -76.5397W The bloom stretched from Colonial Beach, VA to Ragged Point Beach, VA with the mortality epicenter occurring in the region of Westmoreland, VA.
Bloom event dates (yyyy/mm/dd): Start: 2019-07-24, End: 2019-08-14
Quarantine levels dates (yyyy/mm/dd):
Additional date-related information:


Causative organism known: Yes
Causative Species/Genus: Gymnodinium spp. (2156000 cells/L)
Levanderina fissa (formerly Gymnodinium instriatum)
Co-Ocurring Species/Genus:
Chlorophyll concentration, if known: 196 ug/L max µg/l
Additional bloom information: dark waters are domianted by L. fissa, bright green-grey waters are dominated by bacteria and ciliates and were hypoxic or anoxic.
Event-related bibliography:

Environmental Conditions

Weather: Turbidity (NTU): Wind direction:
Stratified water: Oxygen content (nL/L): Wind velocity:
Temperature (°C): Oxygen saturation %: Current Direction:
Sechhi disk (m): Salinity: Current Velocity:
Nutrient information:
Temperature Range During Event: Max: °C, Min: °C
Salinity Range During Event:
Bloom location in the water column:
Growth Comments
Additional Environmental information:

Toxin Assay Information

Species containing the toxin Toxin type Toxin details Max. concentration Assay type
Kit used: Type of kit used:
Additional information:
Economic losses:
Management decision: VDH issued a general safe swimming recommendation to the public advising the public to avoid contact and recreational activities in the vicinity of discolored water and dead fish.
Additional harmful effect information: Reports of 100s of dead fish and crab were received by MD DNR the 3rd week of July. Phytoplankton samples were collected the 4th week of July confirming the presence of a L. fissa bloom, stratified water, and hypoxia in lower portions of the water column.
Created at 05:11 on 8 Apr 2020
Updated at 10:10 on 8 Apr 2020