Expert warns of impact of marine heatwaves on sea life

An expert on Tuesday warned that rising sea and air temperatures in the east Mediterranean are causing marine heatwaves that are, in turn, leading to a proliferation of invasive fish species and jellyfish that threaten to throw delicate habitats off-balance.

“Waters are much warmer in areas experiencing a marine heatwave and this favors the movement of species that are accustomed to higher temperatures, while also pushing out fish that cannot tolerate or feel uncomfortable in them,” Athens University professor of oceanography Serafim Poulos told state broadcaster ERT on Tuesday.

According to Poulos, a marine heatwave is defined as a period of five or more days when the surface temperature of the sea is above the 30-year average, which usually means anything between 2 to 5 degrees Celsius above normal.

“The impact of marine heatwaves comes on top of climate change, which has already heated the country’s seas by 2 degrees Celsius,” he warned.

Commenting on the issue of invasive species like the purple stinging jellyfish that have been making increasing appearances all over Greece since the start of the summer, Poulos said that experts estimate there are already around 800 non-native species invading Greek waters, the most common of which are the lionfish and the silver-cheeked toadfish, both of which are highly toxic and pose a danger to other fish, but also to humans.