The bathing ban has been implemented in Sferrocavalloin Palermo, after that ARPA Sicily detected a high concentration of one toxic microalgae, Ostreopsis ovata. The ordinance, established by the Municipality of Palermo, applies to the coast in front of Viale Florio and will last until ARPA Sicilia finds with new measurements – expected within a week – concentrations within the limit set by law (30,000 cells per litre). Direct contact with the algae causes conjunctivitis and dermatitis and inhalation of the toxin (still unknown) that the algae produces causes respiratory problems, cough, nausea and headache. Their decomposition also has a negative impact on other marine organisms, such as fish, sea urchins and starfish.
What is microalgae Ostreopsis ovata and where it proliferates
Ostreopsis ovata it’s a benthic unicellular microalgae (i.e. it lives by adhering to a rocky or pebbly substrate), typically tropical and sub-tropical, native to the Sea of Japan. Like other alien species coming from tropical seas, it was initially introduced through the so-called “ballast water” of ships and then found the right conditions to proliferate in our seas too. It is therefore one of the species involved in the process of tropicalization of the Mediterranean due to global warming, to which Mare Nostrum is particularly sensitive. The proliferation of Ostreopsis ovata it is mostly due to natural factors, such as high temperatures, warming of the waters and poor water exchange along the coasts.
The microalgae reproduces and proliferates with water temperatures higher than 25°C and poor water circulation, until reaching the stage of flowering, a foamy aggregate of a hazelnut color extending even for a few square meters and with the formation of a sort of mucilaginous film of microalgae adhered to the surface of rocks and pebbles.
This is a phenomenon that is already known Italy (and on other Mediterranean coasts) since the 2000s. After an initial report in Tuscany dating back to 1998, several episodes have been repeated in an increasingly frequent and widespread manner in various areas along the Italian coasts. For example, it was found in Puglia in 2003, in Lazio And Friuli Venezia Giulia in 2006, in the Marche in 2008 and in Sicily in 2012.
What toxic algae can cause: symptoms, effects on health and the environment
During flowering, the algae releases a toxin that is quite dangerous for human health. At the moment it is not certain what exactly the toxin is, but it could be similar to palytoxin, which is very toxic. The toxin mixes with the marine aerosol which moves, transported by the wind, to the coastal strip. Inhalation of this toxin can cause respiratory disorders, cough, nausea, headache in exposed swimmers. Furthermore, direct contact with the microalgae film in water can cause conjunctivitis And dermatitis.
The toxin is also dangerous for other species. In fact, once the flowering phase has passed, the high quantity of decomposing algae causes fish deaths, sea urchins, starfish and benthic organisms. The impact of this microalgae therefore also has economic repercussions due to the decrease in catches and seaside tourism.
When the bathing ban is triggered: the maximum concentration established by ARPA
The bathing ban established for a stretch of the Sferrocavallo coast is envisaged whenever the concentration of algae measured by ARPA exceeds a threshold value. In fact, a program is active in various Italian regions seasonal monitoring of the presence of this microalgae. The control is managed by the ARPA (Regional Environmental Protection Agencies) which also carry out daily sampling in the summer period according to precise protocols. The threshold of attention beyond which an alert is triggered for the proliferation of this species is 10,000 cells per liter in the water columnwhile national legislation provides that, for concentrations greater than 30,000 cells per liter Bathing is prohibited due to risks to human health. The Higher Institute for Environmental Protection and Research (ISPRA) has published specific guidelines for Risk management associated with Ostreopsis ovata blooms on the Italian coasts.
