engleski

Ulva flexuosa Wulfen in fresh and brackish waters of Croatia

Genus Ulva Linnaeus (Ulvophyceae, Ulvales, Chlorophyta) is a cosmopolitan macroalgal genus commonly known as „sea lettuce“. It comprises species living in different aquatic environments, however represents the most frequent coastal seaweed world-wide. Nevertheless, since the mid 1800’s Ulva is being observed in European inland waters as well. At the beginning of the 21st century, massive occurrences of Ulva flexuosa have been noted in European lakes, ponds and rivers, making the genus an obvious dominant element in these waterbodies. In Croatia, a number of specimens involving Ulva (including former Enteromorpha) have been recorded in inland freshwater and brackish sites of northern and middle Adriatic, casually and erroneously described as Enteromorpha intestinalis (Linnaeus) Nees (=Ulva intestinalis) and E. salina Kützing (=U. prolifera). Intrigued by the observed ingress of sea taxa towards freshwaters, we collected specimens from freshwater sites along Eastern Adriatic coast in Croatia while conducting the monitoring of macrophytes. Additionally, macrophyte vegetation surveys were performed and physico-chemical parameters were measured in situ or by Central Water Management Laboratory. In the period 2016-2018 Ulva flexuosa has been recorded in Raša, Mirna, Zrmanja, Cetina rivers, water bodies in the Neretva River Delta and in freshwater spring on the island of Krk. In these locations, salinity ranges were from 0 to 18 PSU, while species occasionally occurred in massive blooms and undoubtedly formed significant habitats in the form of rooted or floating aquatic vegetation. These findings mark the first data about occurrence of U. flexuosa in Croatian fresh and brackish waters.

Ulva ; Croatia ; sea lettuce ; Enteromorpha

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