engleski

Populations of marine alga Polysiphonia subtilissima (Ceramiales, Rhodophyta) in freshwater habitats of Croatia

The ceramialian genus Polysiphonia includes over 207 currently recognized marine species distributed along nearly all the coastlines of the Earth. It is primarily a marine macroalgal genus, with physiological mechanisms underpinning its tolerance to varying salinity. Polysiphonia subtilissima is the only species from the genus recorded in truly freshwater habitats, with three known records: (1) Juniper Creek, Florida, USA, North America ; (2) Jamaica, Caribbean Sea, Central America and (3) Pego-Oliva Natural Park, Spain, Europe. Molecular studies have confirmed that the freshwater populations are conspecific with the marine collections of P. subtilissima. The fourth freshwater record of this species is from the Neretva River Valley, a complex of wetland habitats in the Mediterranean part of Croatia, SE Europe. The alga covered solid submerged surfaces, mainly reed and other aquatic plants, from the surface to approximately 50 cm of depth at salinity levels ranging from 0.4 to 4.59 PSU. Vegetation surveys revealed coverage of P. subtilissima between 5 and 75 %, forming blooms in two sites: a river segment of 7 km and a wetland area of 70 ha. All populations were dense and associated with allochtonous tropical red alga Compsopogon caeruleus and invasive aquatic plant Myriophyllum heterophyllum. The most recent record from Croatia provides new insight into the species’ general distribution, spread into freshwater habitats and its ecological preferences.

Macroalgae ; Mediterranean ; karst river ; karst river ; bloom ; salinity tolerance

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