Potentially harmful microalgae and algal blooms in the Red Sea: Current knowledge and research needs

Harmful algal blooms (HABs) have increased throughout the world's coastal oceans during the last century mostly due to water eutrophication and climate change. These blooms are often accompanied by extreme extensive negative impacts to fisheries, coastal resources, public health and local economies. However, limited studies have reported HAB events in Red Sea coastal waters. This article reviews potentially harmful microalgae in the Red Sea, based on available published information during the last 3 decades. Five harmful algal blooms were recorded in the Red Sea; of which 3 blooms are formed by dinoflagellates (Noctiluca scintillans, Pyrodinuium bahamense, Protoperidinium quinquecorne), one by raphidophytes (Heterosigma akashiwo) and one by cyanobacteria (Trichodesmium erythraeum). Additionally, mangrove swamps in the Red Sea were occupied by cyanobacterial mats, which contain microcystin and saxitoxin-producing species. The existing data in this review could be a catalyst for the establishment of monitoring and management program for HABs and their toxins in Red Sea coastal waters. This review also identifies current research gaps and suggests future research directions. •Potentially harmful algae have become prevalent in the Red Sea coastal waters.•Blooms of toxin-producing species were recorded in coastal waters of some countries.•Cysts of harmful dinoflagellate species in the Red Sea sediments were also presented.•This review will assist Red Sea countries monitor and manage harmful algal blooms.