In late summer and early autumn 2022, an intense bloom of Protoceratium reticulatum-the main yessotoxin (YTX) producer along Chilean coasts and a major threat to artisanal fisheries, the aquaculture industry, and environmental health-was recorded in the Patagonian fjord system. The high YTX levels (>3.75 mg kg-1) resulted in the first ban of shellfish collection in Chile. At Puyuhuapi Fjord, a global "hotspot" of harmful algal bloom events, the cell density of P. reticulatum determined in integrated tube samples (0-10 m) at the end of April 2022 reached 407,000 cells L-1. At the same time, YTX levels well exceeded the regulatory limit by roughly 2.5-fold, with concentrations as high as 9.42 mg kg-1 measured in native populations of the blue mussel Mytilus chilensis. Five different YTX analogues, 45-OH-YTX, COOH-45-keto-YTX, COOH-45-OH-YTX, COOH-YTX, and 45,55-diOH-YTX, were also detected in relevant amounts. While the ban lasted close to 3 months, accumulation and detoxification processes were monitored over a 1-year period. This study assessed the implications of high levels of YTXs and their analogues on the local economy and ecosystem health, given the increase in P. reticulatum blooms predicted for NW Patagonia in the context of a changing climate.
Harmful algal blooms (HABs) of toxin-producing microalgae are recurrent in Patagonian fjord systems. Like toxigenic HABs, high-biomass harmful algal blooms (HB-HABs) have important socio-economic repercussions, but most studies have focused on the former. Here we report the formation and development of an intense HB-HAB of Prorocentrum micans that occurred in Northwest Chilean Patagonia in the late summer (February-March) of 2022. Concentrated and extensive brown spots were visible on the water surface, accompanied at the end of February by a strong odour. Prorocentrum micans cells were detected at relatively low densities (up to 215 cells mL-1) in January but by February 11 cell densities exceeded 1000 cells mL-1, reaching a maximum of 8.3 × 103 cell mL-1 in the surface layer. The high cell densities at Reloncaví Sound and the Gulf of Ancud were closely associated with narrow-ranging increases in the sea surface temperature (17-18.5 °C) and salinity (29-31 g kg-1). Sentinel-2 satellite images from February 22 showed a colour change corresponding to the presence of the brown patches at both locations, consistent with the increases in the normalized index of chlorophyll differences (NDCI) and chlorophyll a concentrations (~50 μg L-1). Satellite images from GHRSST indicated warmer waters in Reloncaví Sound and the Gulf of Ancud than in the Gulf of Corcovado, located 170-km to the south. An oceanographic 3-D model (MOSA) showed surface currents with a cyclonic eddy centred in the Gulf of Ancud. This circulation pattern suggested greater water retention in the study area during January and February, with the drifting and rotation of the coastal currents around the eddy maintaining the P. micans bloom. Thus, the elevated cell density of P. micans in the Gulf of Ancud, near the periphery of the eddy, confirm the presence of a material accumulation hotspot for HABs and HB-HABs.
A recently published study analyzed the phylogenetic relationship between the genera Centrodinium and Alexandrium, confirming an earlier publication showing the genus Alexandrium as paraphyletic. This most recent manuscript retained the genus Alexandrium, introduced a new genus Episemicolon, resurrected two genera, Gessnerium and Protogonyaulax, and stated that: "The polyphyly [sic] of Alexandrium is solved with the split into four genera". However, these reintroduced taxa were not based on monophyletic groups. Therefore this work, if accepted, would result in replacing a single paraphyletic taxon with several non-monophyletic ones. The morphological data presented for genus characterization also do not convincingly support taxa delimitations. The combination of weak molecular phylogenetics and the lack of diagnostic traits (i.e., autapomorphies) render the applicability of the concept of limited use. The proposal to split the genus Alexandrium on the basis of our current knowledge is rejected herein. The aim here is not to present an alternative analysis and revision, but to maintain Alexandrium. A better constructed and more phylogenetically accurate revision can and should wait until more complete evidence becomes available and there is a strong reason to revise the genus Alexandrium. The reasons are explained in detail by a review of the available molecular and morphological data for species of the genera Alexandrium and Centrodinium. In addition, cyst morphology and chemotaxonomy are discussed, and the need for integrative taxonomy is highlighted.