Abstract: Harmful algal blooms represent an emerging risk for marine mammals through the trophic transfer of phycotoxins. This study assessed exposure to domoic acid and paralytic shellfish toxins (PSTs) in short-beaked common dolphins (Delphinus delphis) involved in a mass stranding event in Golfo Nuevo, northern Patagonia, Argentina, in March 2018. Samples from 47 dead dolphins, together with phytoplankton, mesozooplankton and Argentine anchovies (Engraulis anchoita), were analyzed by LC–MS/MS. Domoic acid was not detected in any sample. PSTs were absent from phytoplankton and mesozooplankton, but C1/C2 analogs were detected in anchovies, suggesting a potential trophic pathway. PSTs were detected in blood and kidney samples from 32 dolphins, including adults, juveniles, calves and one fetus. Although a direct causal link with the stranding could not be established, the results provide the first evidence of PST exposure in common dolphins from the Argentine Sea and highlight the potential health risks associated with sublethal phycotoxin exposure in coastal marine predators.
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