ISSN 2519-8513 (Print) Biosystems ISSN 2520-2529 (Online) Biosyst. Divers., 26(2), 160–169 doi: 10.15421/011825 Diversity Long-term dynamics of flora of karst lakes: Changes and current state E. A. Belyakov*, **, E. V. Garin* *Papanin Institute for Biology of Inland Waters RAS, Borok, Russia **Cherepovets State University, Cherepovets, Russia Article info Belyakov, E. A., & Garin, E. V. (2018). Long-term dynamics of flora of karst lakes: Changes and current state. Received 19.04.2018 Biosystems Diversity, 26(2), 160–169. doi:10.15421/011825 Received in revised form 07.05.2018 Long-term observations of the rates and pattern of changes in flora and vegetation contribute to understanding of one Accepted 10.05.2018 of the most important contemporary global problems, the eutrophication of water bodies. In this study, using classical floristic methods, we attempt to determine (for a period of almost 80 years) the nature and possible causes of changes in I. D. Papanin Institute for Biology of Inland Waters RAS, the floristic composition of the lakes of karst origin, Velikoe and Parovoe (Pustinskaya lake-river system, the right bank of Borok, 152742, Yaroslavl Nizhny Novgorod oblast). The paper shows that over a long period of observations a significant transformation of the Oblast, Russia. vegetation cover has occurred in the lakes. The process was accompanied by the disappearance of a number of native Tel.: +748-547-24-042 species and appearance of others, including adventitious ones (for example, Elodea canadensis Michx., Zizania latifolia E-mail: [email protected] (Griseb.) Stapf, Bidens frondosa L. and Epilobium adenocaulon Hausskn.). The weak saturation of the flora with Cherepovets State University, adventive species indicates that the reservoirs are subject to moderate anthropogenic transformation. This is also indicated Lunacharsky Ave., 5, by the presence of characteristic indicator species, for example, Najas minor All., Glyceria fluitans (L.) R. Br., Cherepovets, Vologda oblast, Hydrocharis morsus-ranae L. and Stratiotes aloides L. in the plant communities. In addition, the studied water bodies are 162600, Russia. subject to a further increase in the degree of eutrophication. This can be judged by scattered records of Potamogeton trichoides Cham. et Schlecht., the disappearance of a number of species (such as Elatine alsinastrum L. and Callitriche hermaphroditica L.), as well as the presence of a significant number of macrophyte indicators of the eutrophic state of water bodies. We suggest that a gradual increase in the trophicity of the studied water bodies is due to a combination of anthropogenic impact (water withdrawal for economic needs, recreational load), natural and climatic features of the region (alternation of high and low water periods) and the natural succession processes associated with the current fundamental changes in the conditions of the runoff formation in the Volga River basin. As a result of studies conducted by authors in 2014–2015, it has been shown that in general the taxonomic and ecological structures of the flora of both lakes are quite diverse and traditional for the territory and the European part of Russia. Meanwhile, the flora of these two reservoirs insignificantly differs in taxonomic composition, which is due to their individual morphometric characteristics, the physical and chemical properties of the aquatic environment, and the nature of the anthropogenic load. At the same time, the equilibrium balance of coastal and aquatic plants in the flora of Lake Parovoe (in contrast to Lake Velikoe) indicates a degree of successional stability of its floristic complex. Keywords: eutrophication; vascular plants; adventive species; rare plants; structure of flora; floristic richness Introduction In this context, we are especially interested in Lakes Velikoe and Parovoe of the Pustyn lake-river system in the basin of the Seryozha, Aquatic and shoreline-aquatic plants and their communities are an Teshchia, and Piana rivers on the territory of the forest-steppe right bank important component of the littoral zone of different types of aquatic- of Nizhny Novgorod oblast (Arzamassky District, near the Staraia Pus- swamp ecosystem (Carpenter & Lodge, 1986; Chambers et al., 2008; tyn village) (Bakka & Kiselyeva, 2008). As we have mentioned above Lacoul et al., 2011; Dhanam & Elayaraj, 2015; Sharma & Singh, 2017). (Belyakov et al., 2017), this area is characterized by especially well de- They are an indicator of eutrophication processes – one of the main cur- veloped karst forms of relief, connected with the washing-out of rent global problems (Yang et al., 2008; Sender, 2012; Seo et al., 2014; outcrops of gypsum and limestone-dolomite rocks by the ground and Teneva et al., 2014). By changing the natural environments, aquatic above-ground waters. According to the botanical-geographical zoning, plants can also indicate the extent of anthropogenic impact (Lehmann & the studied lake-river complex is at the junction of the European broad-lea- Lachavanne, 1999; Clayton & Edwards, 2006; Lacoul et al., 2011; ved and Eurasian taiga (coniferous) regions. According to the botanical- Pirini et al., 2011; Pereira et al., 2012; Evangelista et al., 2014; Sharma geographical zoning by Averkiev (1954), the Pustyn lakes are located at & Singh, 2017). It should be mentioned that a rising level of eutrophica- the junction of the Vyksa-Seryozha sub-district of the fir-pine forest tion causes a significantly manifested decrease in the water quality and zone and the Arzamassky-Vadsky sub-district of the forest-steppe zone. is often followed by a decrease in the species diversity in water reservoirs The region is located in the zone of moderate continental climate (Egertson et al., 2004). Therefore, multi-year monitoring of the dyna- with cold and long winters and quite hot, relatively short summers mics of flora and vegetation of different types of aquatic-swamp objects (Bakka & Kiselyeva, 2008). An interesting fact is that on the territory is especially relevant in this context. The results of such studies allow where today the objects of our study are located, was a large pre-glacial one not only to determine the tempi and the pattern of changes that grand-Pustyn lake (over 10 km wide) the age of which was determined occur in different types of plant communities, and to determine their by contemporary scientists (Melnikova, 2014) as Dniprovsky. As Mel- cause-effect relationship, but also to objectively determine of the response of nikova (2014) suggests, the reason for the formation of such a water the biota to the conditions developing in a particular ecosystem. body could have been the ponding of the natural flow of the Seryozha Biosyst. Divers., 26(2) 160 and Oka rivers, and also melted glacial water. During the epoch of de- Results gradation of the glaciation, the periglacial lake was drained off (Melni- kova, 2014). The further development of the karst processes in the channel According to our data, the current flora of Lake Velikoe is repre- of the Seryozha contributed to the development of the large faults which sented by 100 species of 2 orders, 32 families and 63 genera; the flora of exist today and which are filled by the Pustyn lakes among others. The es- Lake Parovoe contains 87 species of 2 orders, 37 families and 64 ge- sential role in the formation of their current condition (along with the nera. It should be mentioned that in the past researchers (Smirnova et al., processes of karst-formation) was played by the alluvial process, “which 1975; Lukina, 1982) did not include in the lists of the lake flora trees added additional features to the morphology of lake basins: enlarged and shrubs which grow here on periodically drying-out shallow water and smoothened the relief of the karst basins to some extent" (Astashin areas and the shoreline. At the same time, several species, Salix and et al., 2016, p. 53). The history of research on the flora and vegetation of Alnus, are familiar to us from different areas of the Pustynskaia lake- the Pustyn Lakes began in the late 1920s. The first botanical surveys of river system since the 1960-s from herbarium collections. It seems that Lake Velikoe were conducted in 1935 by Vorobyev (1943). Data on the this is related to the fact that at that time, the researchers may have flora of this water body are provided in a number of other studies consciously excluded these taxa from the list of the lake flora, as also (Smirnova & Nikitina, 1972; Lukina, 1982; Nikitina, 1982). The floris- with some species of herbaceous plants of excessively moistened habi- tic study of Lake Parovoe was initiated in 1939 by A. D. Smirnova and tats. For more accurate comparison of our data with the existing mate- were continued in 1965–1975 by E. V. Lukina and I. G. Nikitina (accor- rials (in the article further), we excluded the assessment of tree-shrub ding to: Smirnova et al., 1975). vegetation from our list (Table 1). Nevertheless, it should be mentioned The objective of this study to evaluate the pattern and possible rea- that along the shores of Lake Velikoe, we found four species of willows sons for changes of the flora at the Velikoe and Parovoe Lakes during a (Salix alba L., S. cinerea L., S. triandra L., S. viminalis L.) and Alnus period of almost 80-years, as well as its current condition. glutinosa (L.) Gaertn., whereas on Lake Parovoe – only three species – Salix (S. alba, S. cinerea, S. triandra), Alnus glutinosa, Ribes nigrum L., Materials and methods Ulmus laevis Pall. and Tilia cordata Mill. The baseline for this study was given by the material collected by Table 1 the authors (Belyakov et al., 2015, 2017) in collaborative expeditions of Number of taxa of different rank in the macrophyte flora the staff of the laboratory of the aquatic plants of the Institute for Biolo- of Lakes Velikoe and Paravoe over an 80-year period of observation gy of Inland Waters Russian Academy of Sciences and Botany Depart- (without taking into account tree-shrub components) ment of State University of Nizhny Novgorod, conducted in July– Lake Velikoe Lake Parovoe August of 2014 and 2015 at Lakes Velikoe and Parovoe.