Role of Altitude in Formation of Diatom Diversity of High Mountain Protected Glacier Lakes in the Kaçkar Mountains National Park, Rize, Turkey

Abstract

The benthic diatom assemblages of the glacier Avusor Great Lake and Koçdüzü Great Lake were investigated in August 2019. A total of 71 diatom species belonging to 34 genera were determined in the samples, 49 species from Avusor Great Lake and 37 from Koçdüzü Great Lake. Only 15 diatom species were common to both lakes. Total floristic similarity between the neighbouring lakes was only 21.12%. Genera with the highest number of species were Eunotia (8), Gomphonema (6), Pinnularia (6), Navicula (5) and Aulacoseira (4). The diatom flora of both lakes was formed by cosmopolitan species with a large influence from species in alpine and subalpine area. A comparison of the diatom assemblages of the investigated lakes showed differences in both relative abundance and species present in the individual lakes. Bioindicative analysis showed that the water of Koçdüzü Great Lake is more alkaline and less saturated with organic substances than Avusor Great Lake. In both lakes, the communities are composed of species adapted to living in the benthos of fresh waters of moderate temperature well enriched with oxygen. In both lakes, the water quality was Class 2 with a saprobity index of S = 1.08 in Avusor Great Lake and 0.97 in Koçdüzü Great Lake, but their communities were composed of species with both oligotrophic and mesotrophic status. Statistical comparison of the species composition of studied lakes with other high mountain lakes and the lakes in northern Turkey revealed the role of altitude as the main factor in the formation of diatom floras.

The effect of salinity and altitude on diatom assemblages and ecological status assessment based on diatom indices in the lentic systems of the Western Mediterranean Basin (Türkiye)

“…Moreover, species belonging to genera Gomphonema, Navicula , and Encyonema constituted the majority of high ALT optima species in HEF. This result was similar to the study of Şahin and Barinova (2022), which reported a high occurrence of Gomphonema and Navicula species in other high mountain lakes in Türkiye.…”

“…high ALT optima species in HEF. This result was similar to the study of Şahin and Barinova (2022), which reported a high occurrence of…”

“…Among the HEF, the highest species richness and diversity were recorded in Lake Girdev (L2). Şahin and Barinova (2022) have stated that species richness in high mountain lakes in the north‐east of Türkiye increased up to 2000 m a.s.l. and then started to decrease.…”

“…Barinova (2011) has reported the altitude is the primary effective factor for the taxonomical diversity and distribution of freshwater diatoms in Israel. In Avusor Great and Koçdüzü Great lakes, Şahin and Barinova (2022) have found the species belonging to four genera (Eunotia, Gomphonema, Navicula and Pinnularia) constitute the majority in the diatom composition, as in other high mountain lakes in Türkiye.…”

“…Since the human pressure on these lakes is minimal, they are considered suitable environments for examining the effects of natural parameters on littoral diatom communities (Feret et al, 2017; Tornés et al, 2007). Although there are studies on the effect of different parameters on the diatom communities in these lakes (Caballero‐Miranda, 1996; Kernan et al, 2009; Vyverman et al, 2007), the number of studies determining the effect of the altitudinal gradient is relatively low (Barinova, 2011; Clarke et al, 2005; Feret et al, 2017; Şahin & Barinova, 2022). In a study conducted in 209 high‐altitude lakes, it was stated that altitude affects the temperature and ice cover regime of the lakes and consequently, it is responsible for the diatom variation (Clarke et al, 2005).…”