General Information

Event name: US-20-004
Nature of the harmful event:
High Phyto concentration
Event directly affected:
Toxicity detected: No
Associated syndrome: ASP
Unexplained toxicity: No
Species implicated in toxin transmission (transvector):
Report the outcome of a monitoring programme: Yes (Connecticut Department of Agriculture Bureau of Aquaculture (DABA))
Event occurred before in this location: No
Individuals to contact: VAN GULICK, Emily

Location & Date

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Location: Latitude: , Longitude:
General location information: Outer Stonington Harbor, Connecticut
HAB Area code(s): US-07
Additional location information: Elevated concentrations also detected from Guilford-Stonington (eastern Long Island Sound), with a maximum concentration in Waterford.
Bloom event dates (yyyy/mm/dd): Start: 2020-06-04, End: 2020-06-15
Quarantine levels dates (yyyy/mm/dd):
Additional date-related information:


Causative organism known: Yes
Causative Species/Genus: Pseudo-nitzschia delicatissima (70,603 cells/L)
Routine monitoring station at line between Stonington approved and conditionally approved areas (see provided map), but highest concentration during the bloom occurred in Waterford (134,203 cells/L)
Co-Ocurring Species/Genus: Pseudo-nitzschia plurisecta Orive & PĂ©rez-Aicua, 2013 ( cells/L)
Chlorophyll concentration, if known: µg/l
Additional bloom information: This was not a monospecific bloom (up to 21 other diatom genera present, in addition to dinoflagellates).
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: 13.6 °C, Min: 12.1 °C
Salinity Range During Event: Max: 30.8, Min: 27.3
Bloom location in the water column:
In situ
Growth Comments Max/min data based on samples collected from Guilford-Stonington on 6/2/20. Based upon semi-quantitative data collected over the past 2 years by DABA, it appears that Pseudo-nitzschia preferentially occurrs in eastern Long Island Sound (CT) in "offshore" waters (not directly on the coastline or in harbors/rivers/coves).
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: No domoic acid was detected during this bloom or any subsequent blooms in 2020. DA has never been detected in CT, but routine analysis of Pseudo-nitzschia species (genetic) and domoic acid has never been conducted. ASP testing in CT is conducted in response to high Pseudo-nitzschia concentrations.
Economic losses: It is believed there was no economic impact from this closure because this conditionally approved area is not heavily used and the closure was short.
Management decision: Outer Stonington Harbor was closed after the elevated concentrations were detected, and the area was reopened after cell concentrations rapidly declined the following week and domoic acid was never detected in multiple shellfish species in eastern LIS.
Additional harmful effect information:
Created at 10:11 on 19 Apr 2021