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Труды ИБВВ РАН, вып. 85(88), 2019
Transactions of IBIW, issue 85(88), 2019
FIRST DATA ON MACROZOOBENTHOS OF THE ORKHON AND IDER RESERVOIRS
(MONGOLIA)
A. A. Prokin, A. S. Sazhnev
Papanin Institute for Biology ofInland Waters Russian Academy of Sciences 152742 Borok, Yaroslavl Oblast, Russia, e-mail: prokina@mail.ru, sazh@list.ru
Composition and quantitative characteristics of macrozoobenthos of Orkhon (Kharkhorin) and Ider (Tosontsengel) small water reservoirs of Mongolia as well as parts of rivers in the zone of their influence have been studied for the first time. Benthic fauna of the Orkhon section contained 25 species in 2016-2017, 15 species in each year of studies; 32 species have been found in the Ider section in 2016. Drainage regulation leads to a number of rheophilic species disappearing from the fauna, and appearance of stagnophilous species, which, under favorable conditions, create high abundance and biomass of macrozoobenthos. Particularly high rates of quantitative development of macrozoobenthos, exceeding those in most of the country's studied waterbodies, were noted in the Orkhon reservoir in the low-water year of 2017, when the decrease in precipitation coincided with an increase in air temperature compared to 2016.
Keywords: Orkhon (Kharkhorin) HPS, Ider (Tosontsengel) HPS, reservoirs, macrozoobenthos, abundance, biomass, species richness, Mongolia
DOI: 10.24411/0320-3557-2019-10006
INTRODICTION
The construction of hydroelectric power plants (HPS) is associated with the flooding of large land areas, regulation of water objects drainage, which, in the conditions of the arid climate to which Mongolia belongs, is of particular importance due to the instability and vulnerability of aquatic ecosystems to the anthropogenic effect. However, renewable energy is one of the priorities
of the Mongolian energy sector. There are 13 hydroelectric power plants on the territory of Mongolia at the moment. Most of them were built in the first decade of 21st century on watercourses of various types [In-Depth Review..., 2011]. A significant part of them are small hydropower plants with a capacity of under 2 MW, which include Orkhon and Ider (Fig. 1, 2).
Fig. 1. Space images of Reservoirs studied: A - Ider Reservoir, B - Orkhon Reservoir. © Google Earth.
The Orkhon (Kharkhorin) HPS is the first hydroelectric power plant in the country (installed power 525 kW) was built in 1959 [In-Depth Review..., 2011], is not operating now. HPS was formed as a part of irrigation system and consists of spillway dam in the Orkhon River channel, water reservoir and power plant connected with the river by an underground channel (Fig. 2B). Water reservoir area is ~0.02 km2, depth at the dam 1.5 m, coordinates: 47°10.734N, 102°47.384'E, 1475 m. alt.
The Ider (Tosontsengel) HPS (installed power 210+165 kW) was built in 2000 on Ider
River and became operational in June of 2006 [In-Depth Review., 2011]. HPS consists of a spillway dam, water reservoir and power plant (Fig. 2A). Shallow and prone to overgrowth water reservoir is situated above several canals of Ider River and Khodzhulyn River flowing into it. Water reservoir area is ~0.58 km2, depth at the dam 3 m, coordinates: 48°44.488'N, 98°15.312'E, 1705 m. alt.
Macrozoobenthos of these water reservoirs has not been studied previously and it determined the aim of our study.
MATERIALS
Qualitative samples of macrozoobenthos have been collected using Peterson grab with sampled area of 0.025 m2 (2016) and Ekman grab with sampled area of 0.01 m2 (2017), two lifts per sample.
Material was fixed with 75% ethanol, identification was carried out in laboratory. Twelve qualitative samples were collected and processed.
Total number of species, abundance (N, ind./m2) and biomass (B, g/m2) were analyzed during the study of macrozoobenthos structure.
AND METHODS
Water's chemical and physical parameters were analyzed in 2016 using «YSI-85» portable analyzer.
Yearly and seasonal data on air temperature and precipitation in the studied area were obtained via http://www.meteomanz.com.
Space images of studied water reservoirs were taken from Google Earth. Area of the Orkhon reservoir in the period of studies was calculated using Landsat-8 images.
Fig. 2. Water bodies studied (author's photographs): A - Ider River, upstream of the Reservoir; B - Khodzhulyn River; C - Ider (Tosontsengel) HPS dam; D - Ider Reservoir; E - Ider River, downstream of the Reservoir; F - Orkhon River, upstream of the Reservoir in 2017 year; G - Orkhon (Kharkhorin) HPS dam in 2016 year; H - Orkhon River, downstream of the Reservoir in 2016 year; I - dam and Orkhon River, downstream of the Reservoir in 2017 year.
RESULTS
Water temperature decreased in the series from Orkhon River upstream of the reservoir - the Orkhon reservoir - Orkhon River downstream of the reservoir, parallel with decreasing oxygen content and pH and increasing electrical conductivity (Table 1). Water temperature in Khodzhulyn River was lower than in Ider River upstream of the reservoir. Water in the open littoral of the reservoir was colder than in macrophyte beds, in the section of Ider River downstream of the reservoir it was slightly lower than in the open littoral and significantly lower than in the river's section situated upstream of the reservoir. Water in
Khodzhulyn River had the lowest electrical conductivity and pH. The former index fluctuated synchronously with water temperature along Ider River when passing through the reservoir. Oxygen content in the water was stable and pH was insignificantly higher in the river downstream of the reservoir (Table 1). Considering the scatter of the values of the studied water parameters in different areas of the two reservoirs and the associated watercourses, it can be noted that the waters of the two studied areas were characterized by similar physicochemical properties.
Table 1. Characteristics of the studied biotopes, physical and chemical parameters of water in 2016
Station name Zone Depth, m Substrate T, °C EC, ^S/cm 02, mg/l O2, % pH
ORT, ripal 0.2-0.3 gravel, sand 12.6 165 9.0 100 8.09
OR littoral 0.3-0.4 silt, detritus 11.8 166 9.0 98 8.00
ORj ripal 0.3-0.4 gravel 11.4 177 8.9 96 8.00
KR ripal 0.3-0.4 sand, silt 11.2 130 8.9 99 7.94
IRT ripal 0.3-0.4 gravel, sand 13.4 183 8.4 99 8.20
IR open littoral 0.3-0.4 gravel, sand 12.7 142 9.6 112 8.27
littoral, 0.2-0.3 flooded soil, sand 13.2 187 9.6 111 8.25
IRj macrophytes ripal 0.3-0.4 silt, flooded soil 12.6 164 9.1 105 8.57
Note. OR| - Orkhon River, upstream of the Reservoir; OR - Orkhon Reservoir; OR! - Orkhon River, downstream of the Reservoir; KR - Khodzhulyn River; IR| - Ider River, upstream of the Reservoir; IR - Ider Reservoir; IR! - Ider River, downstream of the Reservoir. T - Temperature, EC - Electrical conductivity.
Macrozoobenthos of the Orkhon reservoir and Orkhon River in the zone of its influence was found to contain 25 species: 9 - Chironomidae, 3 of «other» Diptera h Ephemeroptera, 2 -Oligochaeta, 1 - Hirudinida, Bivalvia, Gastropoda, Hydracarina, Plecoptera, Heteroptera, Trichoptera and Coleoptera. Fourteen species were found in the reservoir itself, 15 - in Orkhon River upstream of the reservoir, 9 - downstream
(Table 2). Organisms from the following groups: Hirudinida, Gastropoda, Hydracarina, family Caenidae mayflies, families Limoniidae and Tabanidae dipterans were found in the reservoir, exclusively. Rheophilic Plecoptera, genus Baetis and family Heptageniidae mayflies, and family Hydropsychidae trichopterans were found only in the unregulated sections of Orkhon River.
Table 2. Taxonomic composition of macrozoobenthos in Orkhon Reservoir and Orkhon River in the zone of its impact
Taxa ORT OR ORj
Oligochaeta
Tubifex tubifex (Müller, 1774) + + -
Limnodrilus profundicola (Verrill, 1871) + + +
Hirudinida
Erpobdella octoculata (Linnaeus, 1758) - + -
Bivalvia
Musculium compressum Mousson, 1887 - + +
Gastropoda
Gyraulus stelmachoetius (Bourgignat, 1860) - + -
Hydracarina
Hydracarina sp. - + -
INSECTA
Ephemeroptera
Baetis sp. + - -
Rhithrogena sp. - - +
Caenis miliaria (Tshernova, 1952) - + -
Plecoptera
Agnetina brevipennis (Navas, 1912) - - +
Heteroptera
Micronecta sp. (nymphae) + - -
Trichoptera
Ceratopsyche nevae (Kolenati, 1858) - - +
Coleoptera
Haliplus sp. (larva) + - -
Chironomidae
Orthocladius gr. saxicola + - -
Psectrocladius obvius (Walker, 1856) + - -
Cladotanytarsus gr. mancus + + -
Synendotendipes impar (Walker, 1856) + - -
Stictochironomus crassiforceps (Kieffer, 1922) + + +
Polypedilum tetracrenatum Hirvenoja, 1962 + - -
Cryptochironomus gr. defectus + - -
Chironomus commutatus Keyl, 1960 + + +
Chironomus obtusidens Goetghebuer, 1921 + + +
other Diptera
Idiopterapulchella (Meigen, 1830) - + -
Bezzia aff. kuhetiensis Remm, 1967 + + +
Chrysops sp. - + -
Total: 15 14 9
Note. Designations as Table 1.
The overall abundance of macrozoobenthos littoral of the reservoir itself due to various groups
was low in 2016 (Table 3), reaching values from of macroinvertebrates to 100 ind./m2 in the river
180 ind./m2 in Orkhon River upstream of the res- downstream of the reservoir, where Ceratopsyche
ervoir mainly due to chironomids (77.8% N), and nevae trichopterans dominated (60% N).
Table 3. The total abundance (N, ind./m2) of macrozoobenthos of Orkhon Reservoir and Orkhon River in the zone of its impact
Таха OR|, ripal zone OR ORj, ripal zone
littoral zone profundal zone
2016 2017 2016 2017 2017 2016 2017
Oligochaeta 20 2000 40 - 25750 - 150
Hirudinida - - 40 - - - -
Bivalvia - - - - 500 - 50
Gastropoda - - 20 - 50 - -
Hydracarina - - - - 50 - -
Ephemeroptera 20 - - - 150 20 -
Plecoptera - - - - - 20 -
Heteroptera - 100 - - - - -
Trichoptera - - - - - 60 -
Coleoptera - 50 - - - - -
Chironomidae 140 27100 40 4400 16750 - 11900
other Diptera - 50 40 - 50 - 50
Total: 180 29300 180 4400 43300 100 12150
Note. Designations as Table 1.
Overall biomass of macrozoobenthos was also low in 2016 (Table 4). Minimal values of the index were noted in Orkhon River upstream of the reservoir (0.22 g/m2) where chironomids constituted the bulk of the community (63.6% B). Community of the littoral was characterized by
the maximum biomass (4.16 g/m2) due to mass development of Erpobdella octoculata leeches (88.5% B). The bulk of the biomass (69.2% B) in river's ripal zone downstream of the reservoir was made up by stoneflies Agnetina brevipennis.
Table 4. The total biomass (B, g/m ) of macrozoobenthos of Orkhon Reservoir and Orkhon River in the zone of its impact
Таха OR|, ripal zone OR ORj, ripal zone
littoral zone profundal zone
2016 2017 2016 2017 2017 2016 2017
Oligochaeta 0.02 1.95 0.06 - 25.10 - 0.25
Hirudinida - - 4.16 - - - -
Bivalvia - - - - 5.65 - 0.15
Gastropoda - - 0.20 - 0.25 - -
Hydracarina - - - - 0.05 - -
Ephemeroptera 0.06 - - - 0.15 0.08 -
Plecoptera - - - - - 0.54 -
Heteroptera - 0.10 - - - - -
Trichoptera - - - - - 0.16 -
Coleoptera - 0.15 - - - - -
Chironomidae 0.14 17.00 0.02 2.10 8.61 - 6.00
other Diptera - 0.03 0.26 - 0.03 - 0.03
Total: 0.22 19.23 4.70 2.10 39.84 0.78 6.43
Note. Designations as Table 1.
The quantitative characteristics of the studied communities increased significantly in 2017 compared to 2016 (Table 3, 4). The total number of communities increased by 24.4-162.8 times, the total biomass in the Orkhon River increased
by 8.2-87.4 times, but decreased in the littoral of the reservoir by 2.2 times. In 2017 community of the latter biotope was represented exclusively by chironomids, which even with a total abundance of 4400 ind./m2 dominated by Stictochironomus
crassiforceps (88.6% N), formed a biomass less than half the leeches had in 2016. Record indices of abundance and biomass of macroinvertebrates (43300 ind./m2, 39.84 g/m2) have been registered in the profundal zone of the reservoir due to the massive development of oligochaetes and chiron-omids: Tubifex tubifex (46.3% N; 50.2% B), Stictochironomus crassiforceps (34.2% N). Chi-ronomids S. crassiforceps (76.8% N; 55.9% B) dominated in the ripal zone of Orkhon River both in terms of abundance and biomass, same as in the ripal zone of the river downstream of the reservoir
Chironomus obtusidens (41.1% N; 18.7% B) dominated.
A total of 32 species - 15 Chironomidae, 4 Ephemeroptera and Trichoptera, 3 Hirudinida, 2 Gastropoda, 1 Crustacea, Hydracarina, Coleoptera and Ephydridae (Diptera) constituted macrozoobenthos of the Ider reservoir and rivers in the zone of its influence. Sixteen species were found in the reservoir and section of Ider River downstream of the dam, while 4-6 species were found in the sections of the Ider and Khodzhulin rivers upstream of the reservoir (Table 5).
where S. crassiforceps (53.9% N; 70% B) and
Table 5. Taxonomic composition of macrozoobenthos in Ider Reservoir and rivers in the zone of its impact
Taxa
KR Щ IR Щ
Hirudinida
Erpobdella octoculata (Linnaeus, 1758) Erpobdella nigricollis (Brandes, 1900) Helobdella stagnalis (Linnaeus, 1758)
Gastropoda Gyraulus chinensis (Dunker, 1848) Radix intermedia (Lamarck, 1822)
Crustacea Gammarus lacustris G.O. Sars, 1864
Hydracarina
Hydracarina sp.
INSECTA Ephemeroptera
Baetis sp.
Ephemerella nuda Tshernova, 1949 Ephemerella sp. Cloeon (Similicloeon) sp.
Trichoptera
Ceratopsyche nevae (Kolenati, 1858) Arctopsyche ladogensis (Kolenati, 1859) Anabolia furcata Brauer, 1857 Trichoptera sp. (pupa)
Haliplus sp. (larva)
Coleoptera
Chironomidae
Monodiamesa sp. Potthastia gaedi (Meigen, 1838) Cricotopus gr. sylvestris Cricotopus gr. bicinctus Orthocladius gr. saxicola Eukiefferiella sp.
Psectrocladius obvius (Walker, 1856) Paratanytarsus confusus Palmen, 1960 Paratanytarsus sp. Tanytarsus sp.
Polypedilum tetracrenatum Hirvenoja, 1962 Stictochironomus crassiforceps (Kieffer, 1922) Cryptochironomus gr. defectus Glyptotendipes paripes (Edwards, 1929) Chironomus commutatus Keyl, 1960
other Diptera
- + +
- - +
- + +
- + -
- + -
+
- + - -
+ + - -
- - + +
- - - +
- + - -
- + - -
- - - +
+ - - -
- - +
- + - -
- - + +
- - - +
- - - +
- - + +
- - - +
- - + -
- - - +
- - + -
- - + -
+ + + -
+ - - -
- - + -
- - + -
- - + -
Hydrellia sp. (pupa) - - + +
Total: 4 6 16 16
Note. Designations as Table 1.
+
Gastropoda and a number of chironomid species are registered exclusively in the reservoir itself, in particular, the predominantly stagnophilous representatives of Cryptochironomus, Glyptotendipes, Chironomus genera. At the same time, rheophilous mayflies Ephemerella nuda and Baetis sp., family Hydropsychidae caddisflies and genus Monodiamesa chironomids are found only in the watercourses associated with the reservoir.
Overall abundance and biomass of communities varied within 140-1820 ind./m2 and 0.210.57 g/m2, correspondingly. Khodzhulyn River ripal zone community had the lowest abundance indices (Table 6, 7), where chironomids Polypedilum tetracrenatum dominated in terms of number abundance (57.1% N), and mayflies Ephemerella nuda in terms of biomass (40% B). Maximum quantitative characteristics were registered in the ripal zone of Ider River downstream of the reservoir where the biggest share of total
Table 6. The total abundance (N, ind./m2) of macrozoobenthos
abundance was made up by different species of chironomids (56% N); biomass - amphipods Gammarus lacustris (60.9% B) and leeches Erpobdella octoculata (24% B). Mayflies Ephemerella nuda (40% N; 33.8 B) dominated in the Ider River upstream of the reservoir. In addition, chironomids Polypedilum tetracrenatum were important in terms of abundance (35% N); caddisflies Arctopsyche ladogensis by biomass (48.5% B). Quantitative indices of reservoir's littoral zone community in Stuckenia sp. macrophyte beds were twice as high as those of the littoral community outside the beds (Table 6, 7), due to Gastropoda living here and greater development of chironomids with two times the number of species. In the community of macrophyte beds, 69.9% of the total biomass was constituted by Radix intermedia, while amphipods Gammarus lacustris (44.6% B) dominated outside the overgrowths.
of Ider Reservoir and rivers in the zone of its impact
Taxa KR, ripal zone IR|, ripal zone IR IR|, ripal zone
open littoral littoral zone, macrophytes
Hirudinida - - 160 - 140
Gastropoda - - - 220 -
Crustacea - - 60 - 520
Hydracarina - - - - 20
Ephemeroptera 20 180 20 - 40
Trichoptera 20 60 - - 20
Coleoptera - - - - 40
Chironomidae 100 160 80 380 1020
other Diptera - - - 20 20
Total: 140 400 320 620 1820
Note. Designations as Table 1.
Table 7. The total biomass (B, g/m2) of macrozoobenthos of Ider Reservoir and rivers in the zone of its impact
Taxa KR, ripal zone IR|, ripal zone IR IR|, ripal zone
open littoral littoral zone, macrophytes
Hirudinida - - 0.42 - 2.68
Gastropoda - - - 3.68 -
Crustacea - - 0.86 - 6.44
Hydracarina - - - - 0.02
Ephemeroptera 0.08 0.50 0.58 - 0.54
Trichoptera 0.06 0.76 - - 0.22
Coleoptera - - - - 0.06
Chironomidae 0.06 0.10 0.07 0.60 0.57
other Diptera - - - 0.04 0.04
Total: 0.20 1.36 1.93 4.32 10.57
Note. Designations as Table 1.
DISSCUSSION
As water passes through the reservoirs its temperature decreases and electrical conductivity increases which is explained by greater depths in the reservoirs compared with rivers and active sedimentation of suspended matter here. These changes of water parameters are also seen on river sections downstream of the reservoirs (Table 1).
Complexes of benthic macroinvertebrates possessing significant differences from the sections of the rivers upstream of the reservoirs and less significant from the sections downstream are formed on silted bottoms under conditions of slowed flow. This is manifested both at the level of species composition and richness, as well as in quan-
titative characteristics. In particular, drainage regulation leads to the disappearance of a number of rheophilic species from the fauna, while stagnophilous species appear, which, under favorable conditions, can provide a high abundance and biomass of macrozoobenthos. We have registered this phenomenon earlier in larger reservoirs of Mongolia [Prokin, 2018].
We associate the significant increase in quantitative indicators of macrozoobenthos of the Orkhon reservoir and areas of Orkhon River in 2017, compared to 2016, while maintaining the same species richness (15 species), with a significant decrease in water consumption and waterbodies' area in 2017 due to a decrease in precipitation (Fig. 3) along with increasing air temperature (Fig. 4). The surface area of the reservoir was 0.028 km2 as of September 30, 2016 and 0.012 km2 as of September 1, 2017.
It should be noted that the level of abundance and biomass of macrozoobenthos in the Orkhon reservoir and Orkhon River in the water-rich 2016 is comparable to the observed in natural lakes and
larger reservoirs of the region [Ayuushsuren, Shcherbina, 2015; Prokin, 2014, 2018; Shcherbina, Ayuushsuren, 2007; etc.], whereas in the water-poor 2017 it exceeded that in most of the studied waterbodies of Mongolia. At the same time, we have observed similar very high rates of macrozoobenthos abundance [Prokin, 2018] in a section of Dzabkhan River downstream of the Taishir reservoir in 2010-2015, when the planned level of its filling was not yet reached. Under these conditions, the flow of water into the river was reduced, while the amount of incoming suspended matter and nutrients, was maximum. We have previously described a similar situation for sections of watercourses downstream of beaver ponds [Prokin, 2012] and natural channels between Mongolian lakes [Prokin, 2014].
Significant interannual changes in the quantitative characteristics of invertebrate communities and level regime of the Mongolian reservoirs dictate the need to continue hydrobiological monitoring of these ecosystems of the region.
Prec., mm
160 г
140 -
120 -
100 -
80 -
60 -
40 -
20 -
0
2016 -■-2017
IV
V
VII
VIII
VI Months
Fig. 3. Seasonal changes in the amount of precipitation (Prec., mm) in the Orkhon reservoir area in 2016-17.
Tav., °C
25
20 ■
15 ■
10 ■
5 ■
0
2016 2017
IV
V
VI Months
VII
VIII
Fig. 4. Seasonal changes in average monthly temperature (Tav., °C) in the Orkhon reservoir area in 2016-17.
ACKNOWLWDGEMENTS We are grateful to A.V. Krylov, D.B. Kosolapov, B. Mendsaihan, A. Dulmaa and Ch. Ayuushsuren for their help in field work, as well as A.V. Kutuzov for help with estimation of Orkhon Reservoir area. Material was collected during an expedition of the hydrobiological team of the "Joint Russian-Mongolian complex biological expedition of the Russian and Mongolian Academies of Sciences", which was performed in the framework of the Russia state assignment (theme number AAAA-A18-118012690105-0).
REFERENCES
Ayuushsuren Ch., Shcherbina G.Kh. Species composition and structure of macrozoobenthos in lake Ulaagchny Khar
(Mongolia) // Inland Water Biology. 2015. Vol. 8, № 4. P. 366-372. In-Depth Review of Energy Efficiency Policies and Programmers: Mongolia. 2011. Brussels: Energy Charter Secretariat. 132 p.
Prokin A.A. Zoobenthos. In: Beaver (Castor fiber L.) as a key species of a small river ecosystem (Prioksko-Terrasnyi
Nature Biosphere Reserve). Moscow: KMK Scientific Press, 2012. P. 77-100. [In Russian] Prokin A.A. Macrozoobenthos at the beginning of the 21st century. In: Yu.Yu. Dgebuadze (ed.) Limnology and Paleolimnology of Mongolia: Proceedings of the Joint Russian-Mongolian Biological Expedition RAS and MAS, Vol. 60. Moscow: Rosselkhozakademia Publishing, 2014. P. 170-185. [In Russian] Prokin A.A. Initial stage of macrozoobenthos formation in reservoirs of Western Mongolia // Inland Water Biology.
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