In recent years, a microalga called Ostreopsis Ovata has prolifered in the Mediterranean. This microalga can be toxic and have adverse effects on both the environment and human health.


An invasive alga known as Ostreopsis ovata has appeared in mass in the Mediterranean in recent years. This microalga can be toxic to marine life and has adverse effects on both the environment and human health. Intent on raising awareness on the presence of this alga, Surfrider Mediterranean is stepping in to monitor its evolution and initiate preventive and informative measures.

What is it?

Usually found in warm tropical waters, Ostreopsis ovata is a microscopic unicellular alga invisible to the naked eye. It is known to breed in calm, shallow, costal environments. Although the precise conditions of its unusual appearance in the Mediterranean Sea remain unknown, its origin is predictably due to the coupling of warming waters and biproducts of maritime transport.

Ostreopsis ovata settles along the floor of the shoreline, on rocks or other algae. In turbulent waters cells can break free from their resting place and enter into the water column. They also can be found in sea spray and blown towards the shore with the wind. When a particular cocktail of conditions are met, the alga can rapdidly reproduce and form brown and sticky clusters, called bloom. 

What are the impacts on environment and health?

Ostreopsis ovata produces a toxin known as palytoxin, which becomes airborn when the micro alga reaches the water's surface. This emanation can cause human health issues such as cough, fever, cold and breathing difficulties. Currently, diagnosed symptoms tend to decrease in 24h to 48h without much complication, but the recent increase of symptoms' appearance and intensity should be acknowledged and more effective controls should be discussed.

Another method of dispersal that is being examined is inhalation of droplets carried by the wind, which is concerning because this method carries the toxin even without direct contact with water.

In addition to the danger for human health, this microalga also harms marine ecosystems. When it appears in the environment, Ostreopsis ovata causes death of benthic organisms (fixed or seafloor creatures) by asphyxiation, and of filtering organisms by ingestion of toxins. Consequently, the accumulation of this microalga greatly disrupts the food chain. 

What can Surfrider Europe do?

Since 2010, Surfrider has been monitoring Ostreopsis ovata in the scope of its Water quality and users Health program. Regular samples are taken from the water column and from macro-algae from 8 sites in the Mediterranean to assess and record the health, environmental situation, and site weather conditions. Surfrider also aims to inform and educate citizens on the emergence of this dangerous sea substance, bringing this issue to light with educational tools and initiating dialogue with local communities and public authorities.

Thanks to a collaboration with scientific research stakeholders and institutions initiating awareness-raising activities among water sports practitioners and citizens, Surfrider has incorporated this new biological parameter into its water quality monitoring network in the zones of water activities. 

With this monitoring, Surfrider aims to control, and ultimately resolve, the socio-economic impacts of this invasive algae, such as infected coastlines, beach closures, bad reputation of seaside resorts, etc.  

Surfrider's current mission is to increase public awareness and risk prevention around this issue. The preservation of water quality remains at the heart of the Foundation's chief objectives. To learn more about what Surfrider is doing to protect and preserve our rivers, lakes, and oceans, please consult the latest report on Water Quality 

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