The prevalence of benthic dinoflagellates associated with ciguatera fish poisoning in the central Red Sea

•Macroalgae samples were collected from the central Red Sea and examined for the presence of Gambierdiscus and Ostreopsis.•Both genera were observed, and significant differences in abundance were detected between the two genera, and among sampling sites.•Multiple isolates established from field samples were morphologically and molecularly identified as Gambierdiscus belizeanus.•Toxicity analysis confirmed G. belizeanus as a ciguatoxin producer. This study confirms the presence of the toxigenic benthic dinoflagellates Gambierdiscus belizeanus and Ostreopsis spp. in the central Red Sea. To our knowledge, this is also the first report of these taxa in coastal waters of Saudi Arabia, indicating the potential occurrence of ciguatera fish poisoning (CFP) in that region. During field investigations carried out in 2012 and 2013, a total of 100 Turbinaria and Halimeda macroalgae samples were collected from coral reefs off the Saudi Arabian coast and examined for the presence of Gambierdiscus and Ostreopsis, two toxigenic dinoflagellate genera commonly observed in coral reef communities around the world. Both Gambierdiscus and Ostreopsis spp. were observed at low densities (