Introduction
At present, there are practically no territories and water areas on the earth's surface that are not affected by human activities. The existing classifications of modern landscapes distinguish anthropogenic landscapes, the structure and occurrence of which are associated with human activity (Milkov, 1973). Artificial water bodies (ponds, watered quarries, canals, reservoirs et al.) are characterized by special hydrologo- hydrochemical conditions and community structure (Waterworks, 1978, Konstantinov, 1986).
The largest artificial water-bodies (canals and reservoirs) were created for the purpose of shipping and energy production. At that, most of reservoirs were formed as a result of regulation of the existing riverbeds, which largely determines the dynamics of their communities (Pidgaiko, 1984). Canals are water supply structures and have artificial riverbed. Specificity of formation of biocenoses in canals is caused by their origin and features of communities of water objects which they connect. By their characteristics, canal communities occupy an intermediate position between typical lake and river cenoses.
In the territory of Vologda region the largest canals are Belozersky by-pass canal and the canals of Severo-Dvinskoy water system. Until the present, hydrobionts of these water objects are not practically studied. Earlier studies of zooplankton of water bodies of the North Dvina sluice system were fragmentary and limited only to lakes (Rivyer, 1978, 1982, 1988, 1992, 2012 etc., Rodionova, 1988).
The purpose of the work is to reveal the features of zooplankton of the canals of North Dvina sluice system as a typical anthropogenic habitat.
Materials
The investigations were carried out on 6 canals of North-Dvina sluice system in June 2010. North-Dvina water system is located in the central part of Vologda region in the territory of “Russky Sever” national park (Fig.1). It was constructed in 1825-1828, it connects the Sheksna and Sukhona rivers thus linking the basins of the Volga and Northern Dvina rivers. By its economical significance, North-Dvina system considerably inferior to the Volga-Baltic. Recently, its importance as a tourist route has been increasing.
Fig. 1. Schematic map of Severo-Dvinsk water system (hydrological sampling sites are denoted by red punch)
At present, the North-Dvina water system consists of the chain of small lakes connected by canals. The lakes of the water system are typical glacial water-bodies. Excluding Lake Siverskoye, all water-bodies are shallow, they are characterized by a pronounced thicket zone occupying up to 50% of the water area (Антипов и др., 1981; Краснова, 1999). Lake Siverskoye is the deepest of the lakes of the water system (maximum depth 25 m) and has a pronounced temperature stratification as well as small development of macrophytes, which occupy 5-10% of the lake area. Unlike lakes, canals are characterized by similar morphometric parameters, which is due to their earlier use as transport routes (Tabl.1). All the canals are characterized by a special wave regime, increased turbidity of water and the absence of pronounced macrophyte thickets.
Table 1. Main morphometric characteristics of the canals of the North Dvina gateway system
| № | The canal name | Objects that the connects canal | Length, км | Average width, м | Depth, м |
| 1 | Toporninskiy | Sheksninsky reservoir and Siverskoye lake | 6.6 | 45.0 | 3.00 |
| 2 | Kuz’minskiy | Siverskoye and Pokrovskoye lakes | 1.3 | 40.7 | 3.00 |
| 3 | Pozdyshskiy (riv. Pozdyshka) | PokrovskoyeandZaulomskoyelakes | 2.7 | 65.0 | 3.00 |
| 4 | 1-stVazerinskiy | Zaulomskoye and Pigasovo lakes | 2.3 | 39.5 | 2.94 |
| 5 | 2-ndVazerinskiy | PigasovoandKishemskoyelakes | 2.8 | 42.5 | 2.94 |
| 6 | Kishemskiy | Kishemskoye lake and Itkla riv. | 2.7 | 38.5 | 3.00 |
Methods
Zooplankton samples were collected in July 2010. The collection was carried out by a small Jedi network (74 microns mesh). A total of 45 samples were taken. Sampling stations were distributed throughout the canals (see Fig. 1). To clarify the species composition of zooplankton, samples were taken from areas occupied by macrophytes. Samples were fixed with 4% formalin. Cameral processing of samples was carried out in the Bogorov chamber in accordance with generally accepted methods in Hydrobiology using modern qualifier (Методика изучения…, 1975; Определитель зоопланктона…, 2010). In the zooplankton composition, the species of rotifers (Rotifera) and crustaceans (Cladocera, Copepoda) were taken into account and determined. The total body length was determined for each organism. The zooplankton biomass was calculated according to the equations for the relationship of individual body mass with body length (Балушкина, Винберг, 1979).
The analysis evaluated the average number and biomass of species and groups, the dominant complex of species (relative abundance more than 5 %) was determined, the Shannon-Weaver’s indices of species diversity (by numbers and biomass of zooplankton), Chekanovsky-Sjörensen of faunal similarity (Песенко, 1982), the average individual weight of zooplankton (Крючкова, 1987) were calculated. To assess the degree of variation of indicators in the calculations, the corresponding results of processing of several hydrobiological samples for each studied water object were used. The comparative analysis uses published data (Гордеева и др., 1978; Ривьер, 1978) and own unpublished materials on zooplankton of small lakes in the North Dvina water system.
Results
33 species were found in the zooplankton of the canals of the North Dvina system, including rotifers-11, cladocerans-15, and copepods – 7. The species richness of zooplankton in separate canals ranged from 17 (Kishemsky) to 28 (Toporninsky) species (table. 2). A feature of the canal zooplankton is the presence of the cold-loving Cyclops scutifer in its composition, which is also characteristic of small lake communities in the water system (Ривьер, 1982). Differences in species richness are mainly due to the different representation of cladocerans in the zooplankton, in particular species from family Sididae and Chydoridae.
Table 2. Taxonomic composition of zooplankton in water bodies of the North Dvina sluice system
| Taxon | Canals* | Lakes of the water system | ||||||
| 1 | 2 | 3 | 4 | 5 | 6 | |||
| Тип Rotifera Cuvier, 1817 | ||||||||
| Сем. Philodinidae Bryce, 1910 | ||||||||
| Dissotrocha sp. | – | – | – | – | + | – | – | |
| Rotaria sp. | + | – | – | – | – | – | + | |
| Сем. Euchlanidae Ehrenberg, 1838 | ||||||||
| Euchlanis sp. | + | – | – | + | – | – | + | |
| Сем. Brachionidae Ehrenberg, 1838 | ||||||||
| Brachionus diversicornis (Daday, 1883) | – | + | + | – | – | – | – | |
| Keratella quadrata (Müller, 1786) | + | + | + | – | – | – | +d | |
| K. cochlearis (Gosse, 1851) | – | – | – | – | – | – | +d | |
| Kellicottia longispina (Kellicott, 1879) | – | – | – | – | – | – | + | |
| Сем. Mytilinidae Harring, 1913 | ||||||||
| Mytillina sp. | + | – | – | – | – | – | – | |
| Сем. Asplanchidae Eckstein, 1883 | ||||||||
| Asplanchna priodonta Gosse, 1850 | +d | + | +d | + | +d | +d | + | |
| Сем. Trichocercidae Harring, 1913 | ||||||||
| Trichocerca sp. | – | + | + | + | + | + | + | |
| Сем. Synchaetidae Hudson and Gosse, 1886 | ||||||||
| Polyarthra euryptera Wierzejski, 1891 | – | – | – | – | – | – | + | |
| Polyarthra sp. | + | + | + | + | + | + | + | |
| Сем. Conochilidae Harring, 1913 | ||||||||
| Conochilus sp. | – | – | + | + | – | + | + | |
| Сем. Filiniidae Harring and Myers | ||||||||
| Filinia longiseta (Ehrenberg, 1834) | + | + | +d | + | +d | + | + | |
| Сем. Lecanidae Lemane, 1933 | ||||||||
| Lecane sp. | – | – | – | – | – | – | + | |
| Тип Arthropoda Latreille, 1829 | ||||||||
| Надотряд Cladocera Latreille, 1829 | ||||||||
| Сем. Sididae Baird, 1850 | ||||||||
| Sida crystallina crystallina (O. F. Müller, 1776) | + | – | – | + | – | + | + | |
| Diaphanosoma brachyurum Lievin, 1848 | + | + | – | + | – | + | + | |
| Сем. Daphniidae Straus, 1820 | ||||||||
| Daphnia сristata Sars, 1862 | + | + | + | + | + | + | + | |
| D. сucullata Sars, 1862 | + | + | + | + | + | + | + | |
| D. longispina O. F. Müller, 1785 | – | – | – | – | – | – | + | |
| D. longiremis Sars, 1862 | – | – | – | – | – | – | + | |
| Ceriodaphnia quadrangula (O. F. Müller, 1785) | + | + | + | – | + | + | + | |
| Scapholeberis mucronata (O. F. Müller, 1776) | – | – | – | – | – | – | + | |
| Сем. Bosminidae Sars, 1865 | ||||||||
| Bosmina (Eubosmina) cf. coregoni Baird, 1857 | + | + | – | – | – | – | + | |
| Bosmina (E.) cf. longispina Leydig, 1860 | – | – | – | – | – | – | + | |
| B. (Bosmina) longirostris (O. F. Müller, 1785) | +d | + | + | + | + | + | +d | |
| Сем. Chydoridae Dybowski et Grochowski, 1894 | ||||||||
| Acroperus harpae (Baird, 1834) | + | – | – | + | + | – | + | |
| Alona affinis (Leydig, 1860) | – | – | – | – | – | – | + | |
| A. quadranqularis (O. F. Müller, 1785) | – | – | – | – | – | – | + | |
| A. rectangula Sars, 1862 | – | – | – | – | – | – | + | |
| Camptocercus lilljeborgi Schoedler, 1862 | – | – | – | + | + | – | + | |
| Chydorus sphaericus (O. F. Müller, 1785) | + | + | + | +d | + | + | +d | |
| Disparalona rostrata (Koch, 1841) | + | + | – | + | + | – | + | |
| Graptoleberis testudinaria (Fischer, 1851) | + | – | – | – | + | – | + | |
| Pleuroxus trigonellus (O. F. Müller, 1785) | + | – | – | – | – | – | – | |
| Pleuroxus sp. | + | – | – | – | – | – | – | |
| Сем. Eurycercidae Kurz, 1875 | ||||||||
| Eurycercus (Eurycercus) lamellatus (O. F. Müller, 1776) | – | – | – | – | – | – | + | |
| Сем. Polyphemidae Baird, 1845 | ||||||||
| Polyphemus pediculus (Linnaeus, 1761) | – | – | – | – | – | – | + | |
| Cем. Leptodoridae Lilljeborg, 1861 | ||||||||
| Leptodora kindtii (Focke, 1844) | + | + | + | + | + | + | + | |
| Подкласс Copepoda Milne-Edwards, 1840 | ||||||||
| Cем. Diaptomidae G.O. Sars, 1903 | ||||||||
| Eudiaptomus gracilis (Sars, 1863) | + | + | + | + | + | + | + | |
| E. graciloides (Lilljeborg, 1888) | – | – | – | – | – | – | + | |
| Сем. Temoridae Sars, 1902 | ||||||||
| Heterocope appendiculata (Sars, 1863) | – | + | – | + | – | – | + | |
| Ceм. Cyclopidae Dana, 1846 | ||||||||
| Diacyclops bicuspidatus (Claus, 1857) | + | – | – | – | + | |||
| Thermocyclops oithonoides (Sars, 1863) | – | – | – | – | – | – | + | |
| T. crassus (Fischer, 1853) | – | – | – | – | – | – | + | |
| Mesocyclops leuckarti (Claus, 1857) | +d | + | + | + | +d | |||
| Paracyclops affinis (Sars, 1863) | +d | +d | +d | – | – | +d | + | |
| Cyclops scutifer Sars, 1863 | +d | +d | +d | +d | +d | +d | +d | |
| Cyclops strenuus Fischer, 1851 | – | – | – | – | – | – | + | |
| Megacyclops viridis (Jurine, 1820) | – | – | – | – | – | – | + | |
| Eucyclops serrulatus (Fischer, 1851) | – | – | – | – | – | – | + | |
| Ectocyclops phaleratus (Koch, 1838) | – | – | – | – | – | – | + | |
| Cyclops sp. | + | + | – | + | – | – | – | |
| Harpactiformes | + | – | – | – | – | – | + | |
| Total number of species, including: | 28 | 21 | 17 | 22 | 19 | 17 | 48 | |
| Rotifera | 7 | 6 | 7 | 6 | 5 | 5 | 12 | |
| Cladocera | 14 | 9 | 6 | 10 | 10 | 8 | 22 | |
| Copepoda | 7 | 6 | 4 | 6 | 4 | 4 | 14 | |
Note. «–» – species is not detected, «+» – species is detected, «+d» – dominant view; * – canal designations are similar to table. 1.
The studied plankton communities of canals are characterized by significant equalization (table. 3). The values of the Shannon-Weaver’s indices of species diversity calculated from the number of zooplankton in the canals ranged from 1.8 ± 0.19 (2nd Vazerinskiy) to 3.2 ± 0.18 (Toporninskiy), and from 2.3 ± 0.18 (Kuzminskiy) to 3.1 ± 0.29 (1st Vazerinskiy), which corresponds to indicators in oligo- and mesotrophic reservoirs (Андроникова, 1996).
The average number of zooplankton in the canals of the North Dvina system was 110.2 ± 11.82 thousand specimens / m3, and the biomass was 0.6 ± 0.09 g / m3. The highest values of these characteristics were determined in a small Pozdyshkiy canal (Fig. 2). The dominant numbers and biomass in all the studied canals were Copepoda (see Fig. 2). They ranged from 68 (Kishemsliy) to 85% (2-nd Vazerinskiy) the total number and 67 (1st Aserinsky and Ceselski) to 89 % (Kuzminsky) of the total zooplankton biomass.
Fig. 2. The average abundance (A) and biomass (Б) of zooplankton of canals of Severo-Dvinsky water system (canals are indicated as in Table 1)
The dominant zooplankton complex in all canals is similar and includes 2-3 species. The only exception is Toporninskiy canal, where the composition of the dominant species is more diverse. The dominant species are mainly copepods – Cyclops scutifer, Paracyclops affinis. In separate canals (Toporninskiy, Pozdyshskiy, 2-nd Vazerinskiy, Kishemsliy) rotifers – Asplanchna priodonta and Filinia longiseta are dominant too. The predatory Asplanchna priodonta makes up from 5 (Toporninskiy) to 21% (Kishemskiy) of the total zooplankton biomass, the relative number of Filinia longiseta reaches 6 and 8% in the 2-nd Vazerinskiy and Pozdyshskiy canals, respectively. Among cladoceras, only Bosmina longirostris reaches in the Toporninsky canal the relatively high number and biomass. The share of this crustacean in the total average zooplankton population is 7 %, and in the biomass-2 %. The peculiarity of zooplankton in the canals is their small size, which causes small amounts of total biomass (table. 3). Thus, the average length of sexually matured dominant individuals (Cyclops scutifer and Paracyclops affinis) does not exceed 0.6–0.7 mm. In addition, copepodites make up a significant proportion of the number of these species (up to 10-15% in the sample).
Table 3. Zooplankton indicators of water bodies of the North Dvina sluice system
| Indicators | Canals* | Lakes of the water system | |||||
| 1 | 2 | 3 | 4 | 5 | 6 | ||
| Shannon-Weaver index (бит/экз.) | 3.2 | 2.8 | 3.1 | 2.1 | 1.8 | 3.2 | 2.8 |
| Shannon-Weaver index (бит/г) | 2.9 | 2.3 | 2.5 | 3.1 | 2.4 | 2.7 | 2.5 |
| The ratio of number of Cladocera and Copepoda | 0.36 | 0.10 | 0.03 | 0.14 | 0.06 | 0.19 | 0.22 |
| Average individual weight, mg | 0.006 | 0.005 | 0.007 | 0.002 | 0.002 | 0.004 | 0.012 |
Note. * - canal designations similar to table. 1.
Discussion
Zooplankton of the canals of the North Dvina sluice system is represented by eurybiont organisms that are widely distributed in the region. The basis of the communities are pelagic and bottom species. The continuity of macrophyte thickets causes a small proportion of phytophilic organisms. The registered phytophilic organisms were represented by single individuals, most likely introduced into canals from nearby lakes. The similarity of morphological characteristics and the history of formation cause a significant similarity in the taxonomic composition of zooplankton in all canals, which is confirmed by the values of the Chekanovsky-Sjörensen Index indices (more than 0.7). The most specific, compared to other canals, is the zooplankton composition of the Toporninskiy canal. Macrophyte thickets, including submerged ones, formed on some parts of this water body, which are favorable for the habitat of some cladocerans. In addition, the fauna of this canal is being enriched from the nearby sections of the Sheksninsky reservoir.
After the creation of artificial water bodies, they are populated by organisms that can adapt to new living conditions (Caley, Schluter, 1997; Louette et al., 2008; Hadasova, Kopp, 2014). The few data on the structure of canal communities in the Vologda region indicate that the species composition and structure of the dominant zooplankton complex of these water bodies are determined by water source reservoirs. Thus, for the Belozerskiy bypass canal, the dominance of Kellicottia longispina, Bosmina longirostris, and Eudiaptomus gracilis, which are present as part of the dominant complex in Beloye lake (Думнич, Лобуничева, 2016), is noted. The zooplankton structure of the canals of the Northern slope of the Volga-Baltic water system is also very similar to that of the reservoirs they connect (Лобуничева, 2013). Similar patterns are observed for other canals (Гордеева и др., 1978, Akopian et al., 1999).
Settlement of the canals of the North Dvina water system occurred primarily by organisms from small lakes, which are reservoirs-water sources. These lakes are characterized by a rich zooplankton inherent of meso-eutrophic reservoirs (see table. 2). Differences in the structure of zooplankton in lakes are related to their morphological features. Thus, the zooplankton of the relatively deep-water lake Siverskoye, where hypolimnion is expressed and the highest water transparency is noted (1.5-2 m), is characterized by oligotrophy, in particular low biomass values (0.3-0.4 g / m3). Other lakes are shallow, have a pronounced thicket zone, the water transparency in them does not exceed 1.5 m. In these reservoirs, higher values of zooplankton biomass (Kishemskoe – 0.4 g/m3, Zaulomskoe – 1.4 g/m3 (Ривьер, 1978; own unpublished data)). The structure of the dominant zooplankton complex in all natural reservoirs of the water system is similar.
The dominant group of organisms in all canals were copepoda crustaceans. The predominance of Cyclopidae among zooplankters is directly related to the formation of their communities. In the small lakes of the North Dvina system, the zooplankton is mainly based on Cyclopidae, which is associated with increased turbidity of the water (Ривьер, 1978, 1982). In addition, the absence of a shallow coastal zone occupied by macrophytes in the canals does not allow many species of cladoceras, which are typical for most water bodies in the region, to develop in masse (even in the warmest summer period).
The number and biomass of planktonic animals in the studied canals is slightly higher than in water bodies similar in origin, as well as in small rivers in the region. According to our own research, the average zooplankton biomass in the Belozersky bypass canal and the canals of the Northern slope of the Volga-Baltic water system in the summer is 0.2 and 0.4 g / m3, respectively. Apparently, some increase in the level of zooplankton development in the canals of the North Dvina sluice system is associated with a more pronounced lake regime. The number and biomass of zooplankton in canals with river water sources is significantly lower (Гордеева и др., 1978, Akopian et al., 1999). For reservoirs of the Northern slope of the White sea-Baltic canal, it is indicated that the average zooplankton biomass of the lake part of the canal route is 0.4 g/m3, while in the river part it is only 0.1 g/m3 (Гордеева и др., 1978).
Conclusions
A total of 33 species (Rotifera – 11, Cladocera – 15, Copepoda – 7) were found in the zooplankton of the canals of the North Dvina sluice system. Most species are eurybiont. The taxonomic composition of zooplankton in canals is similar (the Chekanovsky-Sjörensen coefficient is more than 0.7). Initially, the settlement of these water bodies was due to organisms from small lakes and the Sheksninsky reservoir, with which the canals are directly connected. Currently, the penetration of planktonic animals in the canals also happened. However, the morphological features of the canals (simplified bottom relief, absence of a pronounced shallow zone) and wave action determine the structure of the communities formed in them. The almost complete absence of thickets of higher aquatic plants is unfavorable for the development of many zooplankton species. As a result, zooplankton canals are characterized by low species richness with a predominance of pelagic and bottom-dwelling species.
Compared with small lakes, zooplankton canals are characterized by low numbers and biomass, the dominance of a small number of species, and the predominance of small individuals. The structure of the dominant complex is similar. With relatively low numbers and biomass, the basis of zooplankton is made up of copepoda crustaceans. The identified features of zooplankton in canals are directly related to their anthropogenic origin and operation as transport routes. Specific morphological and hydrological characteristics of these water bodies cause a simplified structure and a low level of zooplankton development.
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