Biologia 63/6: 813—823, 2008 Section Botany DOI: 10.2478/s11756-008-0103-2 Terrestrial algae of hypersaline environments of the Central Syvash islands (Kherson Region, Ukraine)* Oxana M. Vinogradova & Tatyana M. Darienko M. G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine, 2, Tereschenkivska St., Kyiv, MSP 01601, Ukraine; e-mail: o.vinogradova@gmail.com, darienko@ukr.net Abstract: In hypersaline environments of the Churiuk and Kuyuk-Tuk islands located in Central Syvash lagoon (Ukraine) 93 species of oxygenic phototrophs (49 Cyanoprokaryota, 29 Chlorophyta, 12 Bacillariophyta, 2 Xanthophyta, 1 Strepto- phyta, 1 Eustigmatophyta) are recorded. The sites studied represent four basic types of habitats: semi-terrestrial ecotone (littoral heavy-loam solonchak free of vascular plants), wet gleyic solonchak covered by sparce halophytic vegetation, gleyic solonetz under saline meadow vegetation, and chestnut solonetzic soil with Steppa salsuginosa formation. They differ in the taxonomic composition and species diversity of algae. The highest species diversity is observed at sites of wet gleyic solon- chaks (71 species of five divisions), the lowest diversity (23 species belonging to three divisions) in the harsh littoral ecotone. The distribution and abundance of species in the four habitats are discussed with reference to their ecology. Descriptions and original drawings of noteworthy taxa of Chlorophyta and Xanthophyta are presented. Key words: oxygenic phototrophs; diversity; hypersaline environments; Syvash; Radiosphaera negevensis var. minor; Chlorosarcinopsis arenicola; Leptosira erumpens; Dilabifilum arthropyreniae; Pseudendoclonium printzii; Gloeobotrys sp.; Capitulariella radians Introduction Hypersaline ecosystems are the striking examples of extreme environments, where organisms exist on the edge of biological limits (Oren & Seckbach 2001). Pho- totrophic biota found in aquatic and terrestrial habi- tats with high salt concentrations include representa- tives of both the bacterial and the eukaryotic domains. Cyanobacteria make a principal contribution to the pri- mary production in these environments and they often determine their biological properties, but eukaryotic al- gae (mostly chlorophytes and diatoms) inhabit them as well (Borowitzka 1981; Gilmour 1990; Oren 2002). However, data on the species diversity of algae found in hypersaline environments are still incomplete and are mainly focussed on benthic mat communities in hyper- saline lagoons, coastal salterns and inland hypersaline lakes (An 1992; Bauld 1981; Campbell & Golubic 1985; Cohen 1984; Oren 2000; Post 1981; Rothschild et al. 1994; Zavarzin et al. 1993). Edaphic phototrophs inhab- iting solonchaks and other types of strongly saline soils are even less investigated (Novichkova-Ivanova 1980; Komaromy 1984; Prikhodkova 1992; Kirkwood & Hen- ley 2006). The Azovo-Syvashsky National Nature Park (ASNNP) in the south of Ukraine (Kherson Region) protects the largest in Central Europe area of hyper- saline (50–300 ‰) lagoons and salt flats of thalassic origin. The Central Syvash ecosystem (45 ◦ 42 ′ N, 33 ◦ 38 ′ E) occupies about 49,000 hectares including water area and numerous small islands. It is the hottest and most arid region of Ukraine. The climate is moderately con- tinental with hot summers and relatively short winters with infrequent snow cover; the annual precipitation is about 260 mm and summer droughts are common. Syvash is a sea gulf of the lagoon type, which was formed as a result of epeirogenic depression and inun- dation of lowlands by sea water. The depth of Syvash does not exceed 1.0–1.5 m, and is in average around 30– 40 cm. In summer-autumn, as well as during periods when water is removed due to strong winds, large areas of Central Syvash turn to subaerial flats covered by salt deposits. The Syvash islands have a natural origin and became separated from the mainland as a result of the of sea current and wind erosion. Churiuk and Kuyuk- Tuk are the elongated, flat loess islands, which are divided into separate strips by numerous bays. Their soil cover is formed by chestnut middle and strongly solonetzic soils together with solonetz and grass solon- chaks. Littoral ecotone is free of vascular plants; higher places are covered by salt marsh, salt meadow and salt steppe vegetation (Andriyenko et al. 1999). Information about the algal diversity in the Syvash lagoon has been summarized in a number of publica- * Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia. c 2008 Institute of Botany, Slovak Academy of Sciences