Harmful dinoflagellate blooms caused by Cochlodinium sp.: Global expansion and ecological strategies facilitating bloom formation

The past two decades have witnessed an expansion in the reported occurrences of harmful algal blooms (HABs) caused by the dinoflagellate Cochlodinium. Prior to 1990, blooms had been primarily reported in Southeast Asia, with South Korea alone reporting more than $100M USD in annual fisheries losses during the 1990s. Since then, time blooms have expanded across Asia, Europe, and North America, with recognition of multiple species and ribotypes that exhibit similar ecophysiological and harmful characteristics. Here, we summarize the current state of knowledge regarding taxonomy, phylogeny, detection, distribution, ecophysiology, life history, food web interactions, and mitigation of blooms formed by Cochlodinium. We review this recent expansion of Cochlodinium blooms and characterize the ecological strategies utilized by Cochlodinium populations to form HABs. Although Cochlodinium is comprised of more than 40 species, we focus primarily on the two HAB-forming species, C. polykrikoides and C. fulvescens, specifically describing their flexible nutrient acquisition strategies, inhibition of grazing by inducing rapid mortality in a diverse set of predators, and allelopathic inhibition of a broad range of competing phytoplankton. Finally, we summarize the available information on prevention, control, and mitigation strategies specific to this genus, and discuss pressing questions regarding this increasingly important HAB organism.