General Information

Event name: ZAF-17-001
Nature of the harmful event:
Water Discoloration , High Phyto concentration , Mass mortalities
Event directly affected:
Toxicity detected: Yes
Associated syndrome:
Unexplained toxicity: No
Species implicated in toxin transmission (transvector):
Report the outcome of a monitoring programme: No
Event occurred before in this location: No
Individuals to contact: MANSFIELD, Lisa

Location & Date

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Location: Latitude: -34.428056, Longitude: 19.186667
General location information: Walker Bay, South Coast, South Africa
HAB Area code(s): ZAF-02
Additional location information:
Bloom event dates (yyyy/mm/dd): Event Date:2017-01-27
Start: 2017-01-14, End: 2017-02-15
Quarantine levels dates (yyyy/mm/dd):
Additional date-related information: This bloom started in late December 2016


Causative organism known: Yes
Causative Species/Genus: Gonyaulax spinifera (611000 cells/L)
Co-Ocurring Species/Genus: Lingulodinium polyedra (Stein) Dodge 1889 (160000 cells/L)
Chlorophyll concentration, if known: >100mg/m3 µg/l
Additional bloom information:
Event-related bibliography: PITCHER, G.C., C. J. FOORD, B. M. MACEY, L. MANSFIELD, A. MOUTON, M. E. SMITH, S. J. OSMOND and L. VAN DER MOLEN 2019 - Devastating farmed abalone mortalities attributed to yessotoxin-producing dinoflagellates. Harmful Algae 81: 30-41.

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
Gonyaulax spinifera Yessotoxins 41a-homoYTX 0.27 mg YTX kg− LC-MS
Kit used: Type of kit used:
Additional information:
Economic losses: ~5.2 million abalone died.Total mortalities from the three farms are estimated to have exceeded 250 tons.
Management decision:
Additional harmful effect information: In addition to the losses of farmed abalone, beaches in the vicinity of the bloom (Sandbaai to the west of Hermanus) were littered with vast numbers of sea urchins (Parechinus angulosus), top snails (Oxystele variegata and Oxystele sinensis), turban snail
Created at 10:19 on 24 Aug 2020
Updated at 10:20 on 24 Aug 2020