The increasing frequency of blooms of nontoxic micro-algae and nuisance macro-algae is harmful because it dramatically reduces sunlight penetration in the water column. Large and long blooms can also draw a substantial amount of oxygen from the water column at night during respiration. Even though these events can occur seasonally, increasing water temperature and OA can change their frequency and intensity favouring the expansion of dead zones \cite{Sherman_2017}

Interaction between stressors

Recent assessments of multistressor effects at global scales show that more than half of the world’s ocean has experienced an increase in cumulative human impact over a 5-y time span, predominantly driven by increasing climate stressors such as sea surface temperature, ocean acidification, and UV radiation \cite{Halpern_2015}.