The invasive brown algae from Asia has been spreading rapidly across the Mediterranean in recent years, now poisoning the daily lives of the inhabitants of the Calanques. The ecological, economic, and health impacts of this proliferation are causing concern, with Thierry Thibaut, an ecology professor, alerting the state services.
Rugulopteryx okamurae is its scientific name. This destructive brown algae from Asia has silently colonized the bay of Marseille for the past ten years, now disrupting the lives of residents in the small port of Callelongue and the Marseilleveyre Calanque.
It is actually a species introduced to France in the early 2000s, which poses a threat to marine biodiversity and can be dangerous for health, similar to the green algae in Brittany, as pointed out by Thierry Thibaut, marine ecologist at the Mediterranean Institute of Oceanology (MIO). France 3 Provence-Alpes investigates this potential threat.
In Callelongue in the Calanques of Marseille, residents are affected, with some even falling ill.
How did this algae colonize the Mediterranean?
Rugulopteryx okamurae first appeared in 2000 in the Thau Lagoon, via oyster trade. “This is quite common unfortunately, aquaculture is the main vector for introducing species,” explains Thierry Thibaut, “because there is no legislation or quarantine.” In 2013, the Japanese algae was spotted in Agde, then arrived in the Calanques of Marseille in 2016, “most likely attached to a sea urchin consumed by a human and then discarded into the sea.” “This is called ‘reverse evolution of biodiversity,’” he explains. It happened due to physical barriers such as oceans and mountains that isolate species.
But with human transportation, we’ve made species travel that should never have moved.
Thierry Thibaut, ecologist at the Mediterranean Institute of Oceanology to France 3 Provence-Alpes
The algae was later found in Spain, Morocco, the Azores, Cape Verde, and the Canary Islands. More recently, it has appeared in Sicily and Algeria.
Its introduction was undoubtedly due to human activity, « because it doesn’t float for long. It fragments into small pieces, and its reproduction is sexual, so it deposits eggs everywhere, which is why we find it throughout the entire bay of Marseille and the Gulf of Lion.” However, its proliferation is not encouraged by climate change, as it thrives in cold to temperate waters.
How is it dangerous to health?
With the tides, the algae detaches, floats a short distance before washing up, forming a thick mat on the beaches. If not cleaned, it decomposes, releasing a rotten egg smell, characteristic of hydrogen sulfide. This gas can be harmful to health when inhaled in high concentrations, potentially causing fainting or even fatal intoxication. “This issue should not be taken lightly,” warns the scientist. “Among those living in Callelongue, some have fallen ill. It’s the same risk as with green algae in Brittany or sargassum in the Caribbean,” another harmful algae with devastating effects.
How does it threaten marine biodiversity?
The ecological impact is significant, as this Japanese algae disrupts the marine ecosystem. In the sea, it covers rocks and alters the habitat of other species. New fish, invertebrates, crustaceans, and mollusks will develop, leading to a disruption in biodiversity.
The disappearance of 60% of terrestrial and marine species on the planet is caused by introduced species. It’s huge, and we don’t talk about it enough.
Thierry Thibaut, professor of marine ecology at the University of Aix-Marseille to France 3 Provence-Alpes
“These are the worst impacts on the planet: habitat destruction, species destruction by invasive species,” says the scientist, lamenting the loss of biodiversity due to this “globalization of species.”
Can we fight this proliferation?
It’s too late to eradicate it in the Mediterranean waters. According to Thierry Thibaut, the only effective way to combat its toxic effects is regular beach cleaning. “It’s easy to remove when it’s fresh, but it must be done very regularly once it starts getting really hot,” explains the ecologist, using Spain as an example, where “considerable resources, amounting to several million euros, are spent every year to remove it before it decomposes and prevent health damage.”
It’s up to state services to act, they do not realize the extent of the ecological damage.
Thierry Thibaut, professor ecologist to France 3 Provence-Alpes
Additionally, the ecologist stresses the need to raise public awareness to promote prevention. “We don’t throw anything living into the sea, nor into our gardens,” says Thierry Thibaut. “We don’t pull up a plant from halfway across the world to plant it at home, and we don’t throw fishing worms from Korea into the Mediterranean.”
Finally, he says, there should be stricter European legislation, modeled after the U.S. or Australia, allowing for more controls to prevent the importation of species threatening environmental balance.
Article originally published on July 27, 2024.
