In 1980 Paralytic Shellfish Poison (PSP) was detected for the first time in Patagonia (Argentina), and has been recurring since during spring and summer .Human intoxications were recorded during the 1987/88 summer due to ingestion of mussels . In January, concentrations of 750000 cells 1 -' were observed, decreasing to 3100 cells 1 -' twenty days later . At the same time, values of 66 150 .Mouse Unit (MU) 100 g -' of meat were measured in Aulacomya ater (a bivalve mollusk) . A decrease in the concentration of toxic plankton resulted in a concomitant decrease in MU values . The mean detoxification time was 7 .6 days . However, mussels retained toxicity up to 50 days after the disappearance of cells .The upwelling of cold waters at the beginning of summer, could have been one of the causes that favoured a bloom of Alexandrium excavatum and of Prorocentrum micans . In March, an abundance of the diatom Skeletonema costatum coincided with high concentrations of silicate .

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Península Valdés (PV) in Argentina is an important calving ground for southern right whales (SRWs, Eubalaena australis). Since 2005, right whale mortality has increased at PV, with most of the deaths (~90%) being calves <3 mo old. We investigated the potential involvement of harmful algal blooms (HABs) in these deaths by examining data that include: timing of the SRW deaths, biotoxins in samples from dead SRWs, abundances of the diatom, Pseudo‐nitzschia spp., and the dinoflagellate, Alexandrium tamarense, shellfish harvesting closure dates, seasonal availability of whale prey at PV and satellite chlorophyll data. Evidence of the whales' exposure to HAB toxins includes trace levels of paralytic shellfish toxins (PSTs) and domoic acid (DA) in tissues of some dead whales, and fragments of Pseudo‐nitzschia spp. frustules in whale feces. Additionally, whales are present at PV during both closures of the shellfish industry (due to high levels of PSTs) and periods with high levels of Pseudo‐nitzschia spp. and A. tamarense. There is a positive statistical relationship between monthly Pseudo‐nitzschia densities (but not A. tamarense) and calf deaths in both gulfs of PV.

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