First identification of Raphidiopsis raciborskii during a heatwave in Lake Comabbio (Northern Italy)

We report the first documented observation of Raphidiopsis raciborskii Wołoszyńska Aguilera et al ..(formerly Cylindrospermopsis raciborskii Wołoszyńska Seenayya et Subba Raju) in Lake Comabbio (Northern Italy) during July 2015 Raphidiopsis raciborskii is an invasive and potentially toxic filamentous cyanobacterium that can produce toxins like cylindrospermopsin and saxitoxins It was originally described as a species of only tropical interest In recent years it has spread worldwide particularly in temperate regions Padisák 1997 mainly because of its tolerance to a wide range of climatic conditions This bloom forming species common in eutrophic waters usually does not generate surface scums and shows a relatively uniform distribution throughout the euphotic zone (Saker et al 2001 Manti et al 2005 The most important drivers for the expansion of cyanobacteria are universally recognised in global warming, eutrophication, hydrological alterations Kokocinski et al 2017 Salmaso et al 2016 Sukenik et al 2012 with multiple factors occurring simultaneously (Heisler et al 2008 Their increase represents a potential significant health threat for animals, humans living and working around the area Its toxins that have been demonstrated to bioaccumulate in aquatic invertebrates ( mollusks) and may lead to fish and birds mass mortalities Heatwaves intensity and duration are expected to increase this century, which are considered favorable conditions for harmful, bloom forming freshwater cyanobacteria The evolving climatic conditions present new risks that should be thoroughly monitored through more frequent surveillance