IntroductionDepending on the elevation, high mountain lakes are located in all latitudes, from the equator to the poles, and have many common characteristics. They are usually characterized by small surface area, shallowness, and poor biodiversity. In addition, low nutrient levels, snow, ice layers, UV radiation, and limited light in high mountain lakes create extreme living conditions for organisms. In recent years, high mountain lakes are increasingly affected by climate change, air pollution, and human activities. High mountain lakes are not resistant to environmental changes and are quickly affected by them. Therefore, they are used as monitoring systems for early warning and are also suitable for biological studies on extreme environments (Psenner, 2003;Catalan et al., 2006).According to the literature, algal studies in high mountain lakes started in the mid-19th century (Lukavský, 1994). Today, the algal floras of many high mountain lakes, such as the Alps, the Pyrenees, the Scandinavian mountains, the Tatras, and the Caucasus, have been investigated (Lukavský, 1994;Banderas-Tarabay, 1997;Tolotti et al., 2003;Barinova and Niyatbekov, 2017). In the framework of the EU project EMERGE (European Mountain Lake Ecosystems: Regionalization, Diagnostics, and Socio-economic Evaluation), algae of high mountain lakes in Europe are investigated (Štefková, 2006).In Turkey, high mountain lakes are located mostly in the Eastern Black Sea region. Studies on determining the algal flora of these lakes were started for the first

The algal flora of 17 lakes and 1 pond in the Artabel Lakes Nature Park were investigated during two summer seasons (2013 and 2016). In total, 26 desmid taxa were found and identified as new records for the desmid flora of Turkey based on their morphotaxonomic characteristics and ecological preferences. The taxa identified belong to the genera Actinotaenium (1), Closterium (1), Cosmarium (15), Micrasterias (1), Spondylosium (1), Staurastrum (5), Teilingia (1), and Tetmemorus (1). Morphotaxonomy, ecology, and distribution of each species were discussed in detail.

Introduction Karagöl-Sahara was declared a national park by the Ministry of Forests in 1994. It is located in the Şavşat district of Artvin in the Eastern Black Sea region of Turkey. The park area is 3304 ha. It is formed by two separate areas, Karagöl and the Sahara plateau. The climate of the region is generally cool and rainy in summer and cold and snowy in winter. According to data from the meteorological station in Şavşat, the annual average temperature and the average annual precipitation are, respectively, 9.8 °C and 737.9 mm (DMIGM, 2001). Karagöl-Sahara National Park is located in the Colchic sector of the Euro-Siberian floristic area in the Holarctic region (Davis, 1965; Zohary, 1973). It is one of the important protected areas of Turkey and is among the world's 25 biologically richest and most endangered terrestrial ecoregions (WWF and IUCN, 1994). In addition, it was identified as one of the world's 200 priority ecoregions by WWF. Karagöl-Sahara National Park is an open laboratory for scientific work thanks to its different habitats and rich plant and animal life. There are many animals (Tetraogallus caspius Gmelin, Vipera kaznakovi Nikolsky, and Ursus arctos L.) and plant genera (Abies,

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The first results of bioindicative analysis of water quality in the high-mountainous lakes of the Artabel Lakes Natural Park are presented using diatom species. A total of 95 diatom taxa collected in August 2013 and 2016 were identified and used as bioindicators for ten environmental variables. Bioindication, statistical methods and comparative floristic results show that the waters in all the lakes studied were fresh, low-saline, with circum-neutral pH and organically uncontaminated. The results of bioindication can be used as etalons for future monitoring of lakes in order to protect species found in the natural park, and can also be included in the national system of water quality standards in Turkey.