Abstract

Species of the potentially toxic diatom genus Pseudo-nitzschia are common components of the phytoplankton community in the fjords and channel systems of the Magallanes Subantarctic region. Despite Pseudo-nitzschia species forming recurrent harmful algal blooms (HABs) in this region, Chilean monitoring programs have historically simply grouped species of this genus into two groups (P. group seriata and P. group delicatissima) according to basic cell morphology under light microscopy, or as Pseudo-nitzschia spp. Based on ultrastructural features obtained from scanning electron microscopy (SEM), this study revealed more diversity within the genus than previously thought, identifying six Pseudo-nitzschia species in the Magallanes Subantarctic region (48°-56°S) from samples collected during a 11-year period (2006–2017). Most importantly, the study: 1) represent the first report on diversity and distribution of Pseudo-nitzschia species in this Patagonian region; 2) expanded the known distribution of P. australis and P. fraudulenta along the Chilean coast (down to 50° S); 3) confirmed previous records of P. pungens and P. cf. delicatissima; and 4) formally confirm the presence of P. heimii and P. calliantha in subantartic waters. © 2022 Elsevier Ltd