Date Published: 20/04/2021
ARCHIVED - Toxic algal blooms likely to become increasing problem in Mediterranean as climate change warms the planet
ARCHIVED ARTICLE
Ostreopsis microalgae blooms have been called “the mother of all plagues”
The Spanish tourist industry is one of the sectors of the national economy which has been most dramatically affected by the coronavirus pandemic, but while there are hopes that progress can soon be made towards reactivating the sector another threat is being reported which could prove even more difficult to counter.
A study carried out by the Institut de Ciències del Mar (ICM) in Barcelona leaves little room for doubt that a genus of highly toxic microalgae of tropical origin known as Ostreopsis is proliferating along the Spanish coastline, its increasing presence due principally to warmer sea temperatures as a result of climate change. These microalgae pose a significant threat for human health, and their ability to cause ophthalmological, digestive, respiratory and dermatological damage is such that they have been referred to as “the mother of all plagues”.
The algae were first observed in the Mediterranean in 2004, and the ICM study concludes that in the next few years they will appear close to the Costas sooner in the year and remain for longer, lasting from spring until autumn rather than being present only in the summer. This study was undertaken as part of the European CoCliME project (Co-development of climate services for adaptation to changing marine ecosystems), which for three years has outlined future growth trends and the impacts of the proliferations of the genus Ostreopsis.
Another conclusion is that although the ostreopsis season will last longer in future years it will be less intense in summer, because sea temperatures will be too warm (between 25.5 and 28 degrees Celsius), although it has not been ruled out that the microalgae may develop an ability to adapt to even warmer conditions.
The Mediterranean is currently warming at a rate of around 2 degrees Celsius per century and the rate of warming has accelerated since the 1990s.
Meanwhile, it is not only the Mediterranean which is experiencing an increase in ostreopsis, and the genus is beginning to appear along the Atlantic coastline in northern Spain.
Ostreopsis are reddish-brown and when they are present in large numbers they can give shallow water the same colour. Their cells produce a range of harmful substances which have been proven to cause death in some creatures such as sea urchins, and so great is their impact on marine ecosystems that in aquariums they been known to kill all other living beings in a matter of hours.
The toxins which are found in the water during algal blooms affect both marine flora and fauna, including shellfish, although no case of food poisoning attributed to these toxins has been found in the Mediterranean. For humans, the main risks are associated according to Elisa Berdalet of the ICM, “with direct exposure to seawater when the cell concentrations of these microalgae are high, and the inhalation of aerosols that contain irritating chemicals. In any case, toxic compounds are only produced under certain circumstances during proliferations.”
These proliferations or blooms occur when the algae multiply excessively in perfect water temperatures, covering the entire seabed and reducing the amount of oxygen in the water.
Sra Berdalet’s CoCliME colleagues Rafael Abós-Herràndiz and Luc de Haro add that “the acute symptoms of this exposure are ophthalmological, digestive, respiratory and dermatological”, but that not enough is yet known about prolonged acute exposure to determine what action should be taken.
What seems clear, though, is that the problem will have to be addressed soon. ICM experts conclude that “given the recurrence and future persistence of Ostreopsis proliferations in Mediterranean tourist areas, these episodes could become a major socio-economic problem in the future”. Various cases of respiratory poisoning by Ostreopsis have already been identified along the Mediterranean coast, and a beach health monitoring and surveillance system has been designed to keep track of the situation.
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