Fig 1.
Environmental conditions associated with A. tamarense bloom in the SLE.
(A) Daily Tadoussac rainfall (mm) (bars) and Mont-Joli airport wind speeds (solid line) and (B) wind direction (degree). (C) A. tamarense cell abundances at Tadoussac (cells L–1) (bars) and Saguenay River runoff (m3 s–1) (solid line). (D) Mollusc toxicity near Bic Island. A. tamarense cell symbols indicate the period of the bloom. See Fig 2 for the geographical positions.
Fig 2.
Location of shellfish and toxic algae monitoring stations and fauna mortalities.
(A) Map of the Estuary and Gulf of St. Lawrence, Canada, showing the location of mollusc and/or toxic algae monitoring stations (numbered from Site 1 to 10), the general summer surface circulation pattern (arrows) and the algal bloom trajectory as simulated by modelling (polygons colour-coded with the date event). (B to D) Position of mammal (X: beluga; square: seals; triangle: porpoises), bird (circle), and fish (diamond) mortality events colour-coded with the event date. For bird and fish mortalities, each symbol may represent several carcasses of the same species. Site 1: Tadoussac, 2: Cacouna, 3: Bic Island, 4: Sainte-Flavie, 5: Mont-Louis, 6: Port-Daniel, 7: Escoumins, 8: Portneuf, 9: Baie Comeau, 10: Sept-Îles.
Fig 3.
Shellfish toxicity and toxic algae monitoring data.
Mollusc toxicity (red bars) and/or the abundance of A. tamarense (open circles) recorded at 10 selected monitoring sites in the Estuary and Gulf of St. Lawrence (see Fig 2). The horizontal red lines indicate the level of toxicity considered hazardous for human consumption.
Table 1.
Concentrations of paralytic shellfish toxins (PST) in tissues of dead specimens collected on beaches or drifting.
Diet: major diet. B: birds, F: fish, M: molluscs, Ma: other macro-invertebrates, N: necrophage, Pl: plankton. For more details of specific tissues sampled see Extended Data S1–S3 Tables. % +: Percentage of individuals (pool) which tested positive to STX, nd: not detected, (HPLC): Results from High Performance Liquid Chromatography, COD PST likelihood: number of animals/total examined at necropsy for which cause of death (COD) suspected to be PST based on case definition of laboratory documentation of exposure to the toxin, evidence of acute death (good body condition, food in stomach) and the absence of other significant pathologies.
Fig 4.
Observed gross lesions consistent with PST.
Adult, 22 year old, female beluga found dead in the SLE during the A. tamarense bloom. Note blood on the skin of the head. Positive for PST in stomach (63.2 μg 100 g-1) and kidney (7.3 μg 100 g-1) by ELISA and HPLC. Liver tested positive for PST by HPLC.
Fig 5.
Modifications of toxin profile through food web.
Typical toxin profile (in STX equivalents and in % of the total toxicity) determined by LC-MS and LC-pcox-FLD of phytoplankton samples and in the liver and/or stomach, gastrointestinal tract/contents from selected fish, bird and mammal carcasses.