Turkish water supplies ‘under attack’ by zebra mussels: Report

Kardelen Koldaş – ISTANBUL

Zebra mussels, one of the most aggressive freshwater invaders, have been spreading uncontrollably in Turkey for the past 10 years, with experts now warning that the danger is threatening the safety of some cities’ water supplies.

Despite their small size, zebra mussels can cause considerable damage to water structures as they can shorten the life-span of storage dams by as much as 50 percent and cling onto water pipes, causing them to clog up.

The species, which takes its name from the striped pattern on their shells, is native to the drainage basins of the Black Sea, the Caspian Sea and the Aral Sea. The highly invasive mussel has spread throughout Europe to southern Scandinavia and Britain, east into Eurasia and south to Turkey via shipping canals.

The first records concerning the presence of zebra mussels in Turkish freshwaters date back to 1897, when zebra mussels were recorded in the western province Bursa and its surrounding freshwater.

Fouling problems by zebra mussels in hydro power plants across Turkey were first determined at the Kovada I Hydroelectric Power Plant in the western province of Isparta in 1964, but with the colonization of this species becoming much more invasive over the last 10 years, experts are now stressing the importance of control strategies.

According to a 2017 report penned by former State Hydraulic Works (DSİ) executives Seyit Aksu and Dursun Yıldız and current DSİ employee Aysen Pervin Güngör, “zebra mussel densities can be so high that the diameter of pipes at some water treatment facilities have been reduced by two-thirds.”

“Zebra mussels cause expensive problems, blocking pipes that deliver drinking and processed water to cities and factories and cooling water to power plants,” read the report titled “How Zebra Mussels Threaten Water Supply Security and the Effects of Preventive Measures in Turkey.”

The Kesikköprü Dam on the Kızılırmak River, one of the most important water supplies of the capital Ankara, is currently under a “zebra mussels attack,” Aksu told daily Hürriyet.

“There is also risk of complete blockage of drinking water pipes. It they are completely clogged, water would not arrive to Ankara,” he added.

Prof. Dr. Naime Arslan, head of the Hydrobiology Department at Eskişehir Osmangazi University, told daily Hürriyet that the life-span of storage dams should be around 150 years but the presence of zebra mussels cuts this life-span in half.

There are fish species that feed on zebra mussels, but as these fish might have damaging effects on other aqua species the “most ideal way” to clean water systems of invasive zebra mussels is to apply an effective amount of ozone to the infrastructure, said Ertan Ercan from Muğla University’s Faculty of Aquaculture.