| Event name: | US-20-005 | |
| Country: | UNITED STATES | |
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Nature of the harmful event: |
Water Discoloration , Seafood toxins | |
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Event directly affected: |
Other Terrestrial , Shellfish | |
| Toxicity detected: | Yes (Approximate range: 1.5-5.7 ppb microcystin-RR in oysters) | |
| Associated syndrome: | OTHER | |
| 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: | Latitude: , Longitude: | |
| General location information: |
Greenwich Cove, Connecticut HAB Area code(s): US-07 |
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| Additional location information: | ||
| Bloom event dates (yyyy/mm/dd): | Start: 2020-07-17, End: 2020-12-08 | |
| Quarantine levels dates (yyyy/mm/dd): | ||
| Additional date-related information: | ||
| Causative organism known: | Yes | |
| Causative Species/Genus: |
Microcystis aeruginosa
( cells/L)
<5-10% phytoplankton composition of samples from Greenwich Cove. Microcystis was not present in Binney Pond on 7/17. Dr. Dianne Greenfield, a DABA colleague, confirmed the presence of Microcystis aeruginosa in subsequent samples she collected. |
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| Co-Ocurring Species/Genus: | ||
| Chlorophyll concentration, if known: | µg/l | |
| Additional bloom information: | No cyanobacteria blooms were observed by DABA staff in freshwater or estuarine environments. Phytoplankton samples revealed the presence of "stressed" Microcystis colonies in Greenwich Cove (<5-10% composition of samples). Greenwich Cove was precautionarily closed on 7/16. Oyster samples taken from Greenwich Cove (commercial lots: Mayhew North and Mayhew South) both had low concentrations of microcystin-RR (3.2 and 3.0 ppb, respectively). Microcystin-RR was present in the Mayhew South lot oysters for multiple months (maximum concentration 5.7 ppb on 9/29); however, it was never detected in the adjacent Mayhew North lot again. Testing of Mayhew South was sporadic due to the expense of UPLC-MS/MS testing (~$250/sample), slower turn-around-time than in-house testing performed by the DABA lab, and the knowledge that shellfish can take an extended period of time to depurate cyanotoxins (weeks-months). Given staff limitations, the area was not surveyed again for blooms (and no blooms were reported again), but oyster testing continued until MC-RR was no longer detected. The maximum MC-RR concentration from Mayhew South was detected on 9/29; therefore, subsequent blooms could have occurred and were not reported to DABA, or MC-RR concentrations in oysters increased naturally during the depuration process (which has been noted in multiple shellfish cyanotoxin depuration studies). | |
| Event-related bibliography: | ||
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| Nutrient information: | ||||||||||||||||||||||||||
| Temperature Range During Event: | Max: °C, Min: °C | |||||||||||||||||||||||||
| Salinity Range During Event: | ||||||||||||||||||||||||||
| Bloom location in the water column: | ||||||||||||||||||||||||||
| Growth: | Advected | |||||||||||||||||||||||||
| Growth Comments | Microcystis bloom advected from freshwater ponds to Greenwich Cove | |||||||||||||||||||||||||
| Additional Environmental information: | ||||||||||||||||||||||||||
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| Kit used: | Type of kit used: | |||||||||||
| Additional information: | UPLC-MS/MS performed by UCONN Center for Environmental Sciences and Engineering (CESE). Limit of detections reported as: cylindrospermopsin (3.0ppb), anatoxin A (1.7ppb), microcystin-RR (1.5ppb), microcystin-YR (15ppb), microcystin-LR (15ppb), microcystin-LA (7.5ppb). Note that the LOD for microcystin-RR is much lower than the other microcystins, and there are 250+ variants; therefore, it is possible that other MCs were present in oysters, but only MC-RR was detected due to low concentrations and testing limitations. The DABA also screened 2 oyster samples in July for saxitoxins using PSP scotia rapid test kits (FDA approved limited use method), which were negative. | |||||||||||
| Economic losses: | The total commercial economic loss due to closures was estimated at ~$125,000, which compounded additional losses due to COVID-19. There is a recreational (conditionally approved seasonal) area in Greenwich Cove. The reopening was delayed ~1 month. | |||||||||||
| Management decision: | Since cyanotoxins are not yet regulated by the FDA in shellfish, the DABA left the area precautionarily closed until MC-RR was no longer detectable. Mayhew North was reopened in August, while Mayhew South remained closed until December. | |||||||||||
| Additional harmful effect information: | While this was not reported, Binney Pond is surrounded by a park and DABA staff observed many children, families, and dogs at the park on 7/17 during bloom investigation. It is possible that there is a human health impact from exposure to bloom water. | |||||||||||
