<i>Mesodinium–Dinophysis</i> encounters: temporal and spatial constraints on <i>Dinophysis</i> blooms

Species of the <i>Dinophysis acuminata</i> complex are the main cause of diarrhetic shellfish poisoning worldwide. These mixotrophs perform photosynthesis with plastids stolen from specific ciliate prey. Current transport models forecast advection of established populations, but modelling bloom development and maintenance also needs to consider the prey (<i>Mesodinium</i> spp.) of <i>Dinophysis</i>. Predator and prey have distinct niches, and <i>Dinophysis</i> bloom success relies on matching prey populations in time and place. During autumn 2019, red tides of <i>Mesodinium rubrum</i> in Reloncaví Fjord, Chile, were not followed by <i>Dinophysis</i> growth<i>.</i> The dynamics of <i>Mesodinium-Dinophysis</i> encounters during this and additional multiscale cases elsewhere are examined. Analogies with some classic predator-prey models (match-mismatch hypothesis; Lasker's stable ocean hypothesis) are explored. Preceding dense populations of <i>Mesodinium</i> do not guarantee <i>Dinophysis</i> blooms if spatial co-occurrence is not accompanied by water column structure, which leads to thin layer formation, as in Lasker's stable ocean hypothesis or if the predator growth season is over. Tracking the frequency of vacuolate <i>Dinophysis</i> cells, irrefutable signal of prey acquisition, with advanced <i>in situ</i> fluid-imaging instruments, is envisaged as a next-generation tool to predict rising <i>Dinophysis</i> populations.