Combined effects of hypoxia and starvation on the survival and growth rates of autotrophic, mixotrophic, and heterotrophic dinoflagellates

Global warming is exacerbating coastal hypoxia by intensifying stratification. Marine hypoxia often causes large-scale mortality of fish, shellfish, and mammals. However, there have only been a few studies on the effect of hypoxia on dinoflagellate survival. Here, we explored the hypoxic effects on the growth rates of dinoflagellates with different trophic modes: autotrophic Alexandrium fraterculus and Scrippsiella lachrymosa ; mixotrophic Alexandrium pohangense , Gymnodinium smaydae , and Shimiella gracilenta ; and heterotrophic Gyrodinium dominans and Protoperidinium pellucidum . Additionally, we tested feeding as a tactic to reduce hypoxia-induced mortality. Hypoxia reduced the growth rates of all the tested species. However, feeding suitable prey to A . pohangense , G . smaydae , S . gracilenta , G . dominans , and P . pellucidum reduced their mortality due to hypoxia. Furthermore, feeding enabled A . pohangense and G . dominans to survive under hypoxic conditions. Therefore, feeding could be used as a strategy for survival and reduction of mortality in mixotrophic and heterotrophic dinoflagellates against hypoxia.