The project ‘Tropicalization and ciguatera in the Canary Islands’ seeks to study the biodiversity of the genus Gambierdiscus, which causes ciguatera, and the relationship that this organism has with the changes derived from tropicalization in the microalgae communities of the Canary Islands.

The warming of the oceans is causing tropical species to appear in subtropical and temperate latitudes. This is a recent phenomenon on the coasts of southern Europe. Thus, benthic microalgae that cause ciguatera syndrome (a common form of food poisoning due to the ingestion of fish that feed on or live on coral reefs) have already appeared in the waters of the Canary Islands.

The project ‘Tropicalization and ciguatera in the Canary Islands’ is an initiative of the Spanish Institute of Oceanography (IEO), which has the support of the Biodiversity Foundation through its call for grants, has studied the biodiversity of the genus Gambierdiscus, which causes ciguatera, and the relationship that this organism has with the changes derived from tropicalization in the communities of microalgae in the waters that bathe the Canary coasts.

The project aimed to analyse the effect that the increase in temperature has on the expansion of these microalgae,working in three areas: on the one hand, to study the level of tropicalization of the Canary Islands based on the abundance of Gambierdiscus species on the coasts of the archipelago; on the other hand, to assess the risk of the expansion of ciguatera on the coasts of the Canary Islands based on the growth of the Gambierdiscus as a function of temperature, salinity and light intensity, and, in addition, to raise awareness of the emerging problem of ciguatera in areas of the EU coast, proposing management actions.

The dinoflagellate distribution Gambierdiscusen has been studied in the seven main islands of the Canary archipelago. By means of a morphological study of the five species detected on the islands, the distribution by species of this genus (G. australes, G. caribaeus and G. carolinianus, G. excentricus, G. silvae) in La Gomera and Fuerteventura was obtained. These data were compared with those from genetic analyses, and it was found that G. excentricus is the most abundant species on the two islands, and yet G. caribaeus was more abundant in La Gomera than in Fuerteventura. It has been seen that there are differences in the survival temperature thresholds of the five species detected in the Canary Islands. The species that adapts to colder temperatures (it grows up to 17°C and survives at 15°C) is Gambierdiscus australes and the one that adapts the least—therefore the most tropical species—was Gambierdiscus caribaeus. In addition to ciguatoxins, maitotoxins were detected in all species except Gambierdiscus silvae, pointing to this species as the one with the highest potential risk of involvement in ciguatera.