Multispecies mass mortality in the Beagle Channel associated with paralytic shellfish toxins.

The Beagle Channel is a Subantarctic semi-estuarine environment at the southern tip of South America, where intoxication events associated with harmful algal blooms have been reported since 1886, including a world record in toxicity due to Alexandrium catenella in 1992. Toxic algae affect public health and ecosystem services, particularly mussel aquaculture and fisheries management. During the austral summer of 2022, an intense bloom of A. catenella (5 × 104 cells L-1) occurred in the Beagle Channel, leading to the second most toxic event in the area, with mussel toxicity reaching 197,266 µg STXeq kg-1. This event was synchronous with the mortality of marine organisms from different trophic levels and terrestrial fauna, i.e., two Fuegian red foxes and a southern caracara. Stomach content and liver samples from dead kelp gulls (Larus dominicanus), Magellanic penguins (Spheniscus magellanicus), papua penguins (Pygoscelis papua), and imperial cormorants (Leucocarbo atriceps), presented variable paralytic shellfish toxins (PST) levels (up to 3427 µg STXeq kg-1) as measured by high performance liquid chromatography (HPLC), suggesting that deaths were associated with high PST toxicity level. The different toxin profiles found in phytoplankton, zooplankton, squat lobsters (Grimothea gregaria), Fuegian sprat (Sprattus fuegensis), and seabirds evidenced possible toxin transformation along the food web and the possible transfer vectors. The unexpected detection of PST in terrestrial fauna (up to 2707 µg STXeq kg-1) suggested intoxication by scavenging on squat lobsters, which had high toxicity (26,663 µg STXeq kg-1). PST trace levels were also detected in a liver sample of a dead false killer whale (Pseudorca crassidens), an oceanic odontocete stranded on the coast during the bloom. Overall, our results denote the exceptional nature of the toxic, multispecies mortality event and that toxins may propagate to several levels of the food web in this Subantarctic environment.

Contrasting phylogeographic pattern among Eudyptes penguins around the Southern Ocean.

Since at least the middle-Miocene, the Antarctic Polar Front (APF) and the Subtropical Front (STF) appear to have been the main drivers of diversification of marine biota in the Southern Ocean. However, highly migratory marine birds and mammals challenge this paradigm and the importance of oceanographic barriers. Eudyptes penguins range from the Antarctic Peninsula to subantarctic islands and some of the southernmost subtropical islands. Because of recent diversification, the number of species remains uncertain. Here we analyze two mtDNA (HVRI, COI) and two nuclear (ODC, AK1) markers from 13 locations of five putative Eudyptes species: rockhopper (E. filholi, E. chrysocome, and E. moseleyi), macaroni (E. chrysolophus) and royal penguins (E. schlegeli). Our results show a strong phylogeographic structure among rockhopper penguins from South America, subantarctic and subtropical islands supporting the recognition of three separated species of rockhopper penguins. Although genetic divergence was neither observed among macaroni penguins from the Antarctic Peninsula and sub-Antarctic islands nor between macaroni and royal penguins, population genetic analyses revealed population genetic structure in both cases. We suggest that the APF and STF can act as barriers for these species. While the geographic distance between colonies might play a role, their impact/incidence on gene flow may vary between species and colonies.