Algal blooms force swimming bans across Italian coasts

Record heatwaves in Italy have sharply raised sea and freshwater temperatures, triggering massive proliferations of algae along the Mediterranean and Adriatic coasts. The blooms have turned water shades of green, yellow and brown and include toxic species such as Ostreopsis ovata, as well as non‑toxic but discoloring organisms like Pyramimonas and Alexandrium cf. taylori. An international study also confirmed the presence of the invasive Australian alga Caulerpa cylindracea in the Adriatic.

Health officials warn that some algae can cause respiratory problems, fever, nausea and eye inflammation. Local authorities from Apulia through Lazio to Tuscany have deployed special response teams, issued warnings and imposed temporary swimming bans at beaches near Molfetta, Giovinazzo, Santa Marinella, Palermo, Marina di Pisa and Janova. In the Po River near Turin, extensive green mats have clogged canals, and more than 1,000 tons of algae were removed from Lake Iseo. Similar concerns have been noted for Croatia’s coastline, though water quality there remains relatively high.