The results of this research, in which the Marine Organism Ecophysiology Group (EOMAR) of the University Institute of the ULPGC collaborated, reveal the presence of Gambierdiscus australes in 75 percent of the samples collected.
The Marine Organism Ecophysiology (EOMAR) group, part of the ECOAQUA University Institute at the University of Las Palmas de Gran Canaria (ULPGC), through Emilio Soler Onís, also a member of the Canary Islands Harmful Algae Observatory (OCHAB), has participated in a study that has confirmed for the first time the presence of the genus Gambierdiscus on the Spanish peninsular coast.
As part of this research, carried out in collaboration with the Ramón Margalef Multidisciplinary Institute for Environmental Studies (IMEM) at the University of Alicante (UA), which led the study, the species Gambierdiscus australes, a microalga from the marine dinoflagellate group that produces ciguatoxins, a set of toxins that cause food poisoning related to the consumption of fish that have accumulated an excess of these harmful agents in their tissues, known as ciguatera, has been identified on the coast of Dénia and Xàbia, in the north of the province of Alicante.
EOMAR researcher Emilio Soler Onís participated in this research.
The finding, recently published in the journal Harmful Algae News, a newsletter edited by UNESCO's Intergovernmental Oceanographic Commission (IOC) that deals specifically with toxic algae and algal blooms, was made based on routine phytoplankton sampling by the UA-Dénia Marine Laboratory, belonging to the IMEM, with the support of researchers from EOMAR, specialists in harmful microalgae and ciguatoxins in Canary Island and Atlantic waters.
Gambierdiscus australes under a scanning electron microscope. Source: University of Alicante.
The study includes two sampling campaigns carried out in March and September 2023 at 12 stations distributed across six coastal areas, both near the coast, at around 250 meters, and further away, at 1 km or more.
The data obtained reveal that Gambierdiscus australes was present in 75% of the March samples and in 100% of the September samples, with abundances ranging from 20 to 140 cells per liter. This is a genus of microalgae that produces ciguatoxins, which can accumulate in large specimens of certain fish species and cause toxicity problems in humans.
Reassurance for consumers
Both UA and EOMAR–ECOAQUA researchers insist that, in light of these results, consumers can rest assured, as the concentrations detected are not alarming and the australis species is not among the most toxic of its genus. Fish that reaches the market undergoes controls and analyses that allow for the detection of possible elevated toxin levels before distribution, thus maintaining food safety.
The research team, which in addition to Soler Onís included César Bordehore, professor in the Department of Ecology at the UA and researcher at IMEM, as well as Eva Fonfría Subirós and John Yañez Dobson, both from IMEM, links the appearance of Gambierdiscus in the Mediterranean Sea to the increase in sea temperature and the expansion of species typical of warm tropical waters to more temperate latitudes.
Gambierdiscus australes under an inverted optical microscope. Source: University of Alicante.
The researchers emphasize that even moderate increases in temperature can favor the colonization of new areas by these microalgae.
Monitoring
Since 2010, systematic monitoring has been carried out on more than 40 kilometers of coastline in northern Alicante, which has made it possible to verify that 15 years ago the genus Gambierdiscus was not present in the area.
This study, in which EOMAR–ECOAQUA is participating, confirms the expansion of Gambierdiscus distribution in the western Mediterranean and emphasizes the need to maintain specific monitoring programs for potentially toxic benthic phytoplankton in order to anticipate risks and ensure food safety.