crossed by a dam, the Cheboksary Reservoir, the last ... AbstractâPresent-day quantitative and qualitative characteristics of the Cheboksary Reservoir have ...
Water Resources, Vol. 31, No. 3, 2004, pp. 316–322. Translated from Vodnye Resursy, Vol. 31, No. 3, 2004, pp. 347–353. Original Russian Text Copyright © 2004 by Nazarova, Semenov, Sabirov, Efimov.
WATER QUALITY AND PROTECTION: ENVIRONMENTAL ASPECTS
The State of Benthic Communities and Water Quality Evaluation in the Cheboksary Reservoir L. B. Nazarova, V. F. Semenov, R. M. Sabirov, and I. Yu. Efimov Kazan State University, ul. Kremlevskaya 18, Kazan, 420008 Russia Received August 15, 2002
Abstract—Present-day quantitative and qualitative characteristics of the Cheboksary Reservoir have been investigated, and data on the biological diversity of benthic organisms have been compared to those of hydrobiological studies carried out in the region prior to the reservoir construction. The reservoir bottom communities include 75 species and forms of benthos. The reservoir water quality has been evaluated using different methods, including the determination of the degree of morphological structure abnormalities in chironomid larvae, regarded as sublethal indicators of bottom sediment pollution with toxic substances.
INTRODUCTION Integral evaluation of water quality is an important factor of water supply. This determines the high rate and large scale of developing and improving the methods for reliable evaluation of water quality. In addition to determining pollution of water bodies by chemical and physical characteristics, water quality evaluation according to hydrobiological indices is an important component of the system of water pollution control. As is known, zoobenthos is defined as a group of invertebrates, whose existence for the greater part of their life cycle is related to bottom substrates of water bodies. Macrozoobenthos characteristics bear information for revealing sites subjected to chronic pollution, because unlike animal communities inhabiting the pelagic zone, benthos is not prone to considerable active or passive migrations. Studies of qualitative characteristics of macrozoobenthos (fish food base) are of great importance. Bottom communities of most freshwater bodies are represented by three major groups: chironomid larvae, oligochaetas, and mollusks. Oligochaetas and mollusks permanently live on the bottom, whereas chironomids, being larval forms of insects, spend only a part of their life cycle on the bottom of water bodies. Many species of this group manifest a distinct response to the presence of different pollutants in the water mass and bottom sediments, thus serving as indicators of the degree of pollution of the water body. Since the early 1970s, numerous researchers have been thoroughly investigating the impact of chemical pollution of aquatic ecosystems on the phenotypic variability in hydrobiont populations (in particular, chironomids), on the appearance of individuals with pronounced morphological abnormalities and deformities of different parts of their bodies. Investigation of morphological deformities in chironomids is also very
important, because such deformities exhibit a sublethal response of biota to unfavorable impact of abiotic factors and give an idea of latent negative changes in hydrobiont communities, thus allowing for planning preventive measures aimed at improving the environmental state of water bodies. This work is aimed at studying qualitative and quantitative characteristics of macrozoobenthos in the Cheboksary Reservoir (a poorly studied water body in the middle part of the Volga River, playing an important role in the national economy of Russia). DESCRIPTION OF THE REGION In the late 1980s, after the Volga River channel was crossed by a dam, the Cheboksary Reservoir, the last one in the cascade of the Volga reservoirs, was constructed near the town of Novocheboksarsk. The reservoir lies at the boundary of two subzones of the forest zone. Its right bank is in the subzone of mixed coniferous and deciduous forests, whereas its left bank is in the subzone of southern taiga [1]. Northern spurs of the Privolzhskaya Highland stretch to the reservoir right bank. The total design volume of the reservoir is 13.85 km3; water surface area is 2274 km2; normal operating level is 68 m; the average operating level of the reservoir varies from 63 to 64 m; and the average reservoir water depth is 6.1 m. After the Cheboksary Reservoir was filled, two bays appeared, one of which flooded Sura River valley, while the other flooded the Vetluga River valley. In the reservoir section of the Volga River, 28 rivers empty into the Volga (in particular, the Oka and the Sura, which are right-hand tributaries of the Volga; Kerzhenets and Vetluga, which are its left-hand tributaries) [2].
0097-8078/04/3103-0316 © 2004 MAIK “Nauka /Interperiodica”
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Table 1. Layout of sampling sites in the Cheboksary Reservoir in 2000 Station number 402 403 404 405 406 409 410 411
Station number
Sampling site Channel, upstream of the Sura R. mouth Right-bank floodplain, upstream of the Sura R. mouth Right bank, 8 km upstream of Vasil’sursk Channel, 10.5 km upstream of Vasil’sursk Left bank, 13.5 km upstream of Vasil’sursk Channel, downstream of the Khmelevskie Shoals (downstream of Vasil’sursk) 1 km upstream of the Sumka R. mouth the Bol’shaya Yumga River bay
412 413
the Vetluga River, the reservoir section near Melkovka the Vetluga R. left bank, the reservoir section
414 418 420 421
the Vetluga R., the left bedrock bank Sugromskii Yar, the left-bank flood plain, 500 m from the bank Lilovyi Yar, the right-bank flood plain of the Vetluga R. the Malaya Yunga R. bay, near Mumarikha
424 426
the Rutkinskii Bay, 300 m from the Volga R. left bank the Sundyr’ R. bay
MATERIALS AND METHODS Benthos samples collected in summer at 16 sampling stations in the Cheboksary Reservoir (Table 1) were studied. Samples were taken in two replicas with a Petersen dredge (with a coverage of 0.025 m2). The bottom sediment samples were washed through a mill gauze sieve No. 20. The live material was classified into taxonomic groups under the laboratory conditions. Chironomid larvae were preserved in Carnoy fixative, whereas other animals were preserved in a 4% formaldehyde solution. Permanent morphological preparations of chironomid larvae were made according to the technique developed by V.F. Warwick [23]. Fore-Berleze fixative was used as a preservation medium for permanent sides. Glycerin was used to make temporary preparations. Identification manuals of V.Ya. Pankratova [8–10], M. Hirvenoja [17], P.S. Cranston [13], and P. Wiederholm [25] were used in this work. Water quality was evaluated according to the indices of Sladecec [5], Woodiwiss [3], and Shannon [11]. RESULTS AND DISCUSSION Species Composition of Macrozoobenthos All in all, 75 species and forms of benthic organisms belonging to seven classes were found among bottom organisms of the Cheboksary Reservoir. These classes are: insects (Insecta class), bivalve and gasteropode mollusks (Bivalvia and Gastropoda classes), oligochaetas (Oligochaeta), polychaetas (Polychaeta class), leeches (Hirudinea class), and crutaceans (Crustacea class). Insect larvae belonged to three orders: dragon-flies (Odonata), mayflies (Ephemeroptera), and dipterans (Diptera). In the reservoir examined, Diptera was the largest group of species; it contained representatives of two families–Chironomidae and Ceratopogonidae. Chironomid larvae dominated in terms of species diversity (30 species, or 40% of all the benthos species found in the reservoir). Mollusks were represented by WATER RESOURCES
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Sampling site
21 species; and oligochaetas, by 16 species (28 and 21.3%, respectively). In addition, larvae of other periaquatic insects were found (four species), leeches (two species), crustaceans (one species), and polychaetas (one species). As can be seen from Fig. 1, Station 404 was the richest in terms of species diversity. Here, 20 species and forms of benthic organisms, including five species of chironomid larvae, ten species of mollusks, four species of oligochaetas, and one species of leeches were found. At Station 426, 18 species and forms of benthic organisms were found, including five species of chironomid larvae, five species of mollusks, five species of oligochaetas, two species of heleids, and one species of polychaetas. Species diversity of benthic invertebrates at the stations in question is determined by the environmental conditions, in particular, by the variety and abundance of food and habitats. To determine species dominating in terms of the frequency of occurrence in the reservoir, a special classification [4] was adopted, according to which the species found in more than 50% of samples were regarded as Number of species 20
10
0
1 2 3 4 5 6 7 8 9
402 404 406 410 412 414 420 424 403 405 409 411 413 418 421 426 Sampling station number
Fig. 1. Distribution of macrozoobentos group types in the Cheboksary Reservoir. (1) Mollusca; (2) Hirudinea; (3) Polychaeta; (4) Oiligochaeta; (5) Crustacea; (6) Ephemeroptera; (7) Odonata; (8) Heleidae; (9) Chironomidae.
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N, individuals/m2 6000
B, g/m2 300 1 2
200
4000 100
2000 0
402 404 406 410 412 414 420 424 403 405 409 411 413 418 421 426 Sampling station number
0
Fig. 2. Quantitative characteristics of macrozoobenthos in the Cheboksary Reservoir. (1) Number; (2) biomass.
dominating, species found in 25 to 50% of samples, as secondary, and species found in less than 25% of samples were considered as rare. Out of 75 zoobenthos species found in the Cheboksary Reservoir (Table 2), pelophylic chironomid larvae Procladius ferrugineus, Chironomus gr. plumosus, and oligochaetas Limnodrilus hoffmeistri were dominating species; rheophylic predatory chironomid larvae Aspectrotanypus trifascipennis, pelophylic chironomid larvae Cryptochironomous gr. defectus, oligochaetas Isochaetides michaelseni, Limnodrilus claparedeanus, Tubifex tubifex, molluscs Amesoda draparnaldi, Dreissena polymorpha, Euglesia sp., Sphaerium rivicola, and Valvata depressa were minor species. Dragon-flies, leeches, heleids, crustaceans, and mayflies were represented by few species and were not numerous. Species inhabiting silted bottom sediment biotopes (with low flow velocity), which are most typical of reservoir ecosystems, constituted the basis of the species composition. According to [7, 12], 57 species and forms of benthos invertebrates were found in the Volga River section within the modern boundaries of the Cheboksary Reservoir. Sand and silted sand were most typical types of bottom sediments. Psammophytes were represented by oligochaetas Limnodrilus newaensis, colonizers of the Pontocaspian Complex, crustaceans Pontogammarus obesus and Pontogammarus sarsi, as well as mollusks Sphaerium rivicola. In the pelophylic group, oligochaetas Limnodrilus hoffmeistri, chironomid larvae Chironomus semireductus and Chironomus thummi, hammarides Dikerogammarus haemobaphes were dominant. Comparing these and the present-day data, we can conclude that, on the whole, transformation of riverine biocenoses into reservoir did not entail considerable changes in the species composition of benthic fauna. The share of psammophytes slightly decreased (some species of crustaceans and mollusks were not found), which is natural for ecosystems of such types, undergoing the process of transformation,
and is related to the disappearance of psammophylic biotopes. At the same time, the share of pelophylic organisms grew. As compared to the 1970s, a certain increase in the species diversity can be explained by a more thorough investigation of the area of the reservoir itself and the mouths of rivers flowing therein. The amount of zoobenthos in the Cheboksary Reservoir was appreciable (Fig. 2). Its density varied from 240 to 5980 individuals/m2 (averaging 1836.25 individuals/m2), and the biomass varied from 0.176 to 257 g/m2 (the average value being 55.89 g/m2). The greater part of biomass was represented by mollusks, chironomid larvae and oligochaetas. Thus, the macrozoobenthos of the Cheboksary Reservoir can be characterized by appreciable species diversity and considerable abundance. According to the number of species, occurrence at the reservoir stations, number and biomass, mollusks, chironomid larvae, and oligochaetas were dominant groups. Water Quality The Cheboksary Reservoir water quality was evaluated according to Woodiwiss and Shannon indices. Saprobity zones were established according to indicator organisms. At present, there is no common approach for reservoir water quality evaluation by biological indices. If the Woodiwiss index, which has been developed for rivers, is applied to reservoirs, it will give underestimates. Saprobity assessment is hampered by the insufficient number of indicator organisms in the ecosystems that have a structure typical of reservoirs. Most likely, a more reliable classification can be obtained using the Shannon Information Index based on species diversity and differentiation of communities. The drawback of this method is very rough classification of waters according to their quality (dirty–polluted–clean). Therefore, the use of several indices at a time can help obtain more accurate estimates of nearbottom water quality (Table 3). In addition to water quality evaluation using standard techniques, the morphological structure of chironomid larvae was studied. Now the appearance of chironomids with pronounced morphological abnormalities and deformities of different parts of their bodies is unequivocally attributed to the presence of toxic substances in the sites of chironomid larvae sampling [6, 16, 19–21, 24, etc.]. Morphological deformities are generally defined as any changes in the normal configuration, excluding abrasion caused by mechanical impacts of bottom sediment particles. Deformities were found in chironomid larvae of Chironomus genus (gr. plumosus species), Procladius ferrugineous, and Aspectrotanypus trifascipennis at all the sampling sites where these species were found. The calculation of the per cent of deformities in one genus of chironomid larvae showed that the share of individuals with deformiWATER RESOURCES
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Table 2. Occurrence of different species of macrozoobenthos at sampling sites in the Cheboksary Reservoir Taxa
402 403 404 405 406 409 410 411 412 413 414 418 420 421 424 426
Chironomidae Aspectrotanypus trifascipennis Clynotanypus nervosus Dicrotendipes notatus Micropsectra gr. praecox Tanytarsus gr. gregarius Tanytarsus mendax Tanytarsus sp. Paratanytarsus sp. Tanypus punctipennis Tanypus vilipennis Procladius choreus Procladius ferrugineus Psectrocladius (Allopsectrocladius) obvius Psectrotanypus varius Chironomus cingulatus Chironomus muratensis Chironomus gr. plumosus Cryptochironomus gr. defectus Cryptotendipes holstatus Cryptotendipes nigronitens Glyptotendipes gripecoveni Harnischia cultilamellata Harnischia fuscimanus Lipinella arenicola Macropelopia nebulosa Microchironomus tener Paratendipes albimanus Polypedilum gr. nubeculosum Polypedilum gr. Scalaenum Prodiamesa olivacea Chrysalices Tanytarsus Chrysalices Chironomus Heleidae Culicoides nubeculosum Ceratopogogn s.str. Odonata Aeschna cyanea Ephemeroptera Caenis macrura Crustacea Gammarus pulex Oligochaeta Aulodrilus limnobius Chaetogaster setosus WATER RESOURCES
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Table 2. (Contd.) Taxa
402 403 404 405 406 409 410 411 412 413 414 418 420 421 424 426
Eiseniella tetraedra Enchetreus genus sp. Isochaetides michaelseni Isochaetides newaensis Limnodrilus claparedeanus Limnodrilus helveticus Limnodrilus hoffmeisteri Limnodrilus udecemianus Limnodrilus uvenis Lumbriculus variegatus Tubifex tubifex Peloscolex ferox Potamotrix hammoniensis Stylodrilus heringianus Cocoons of Oligochaeta Polychaeta Hypania invalida Hirudinea Helobdella stagnalis Caspiobdella fadejewi Mollusca Anadonta stagnalis Anisus contortus Amesoda draparnaldi Amesoda scaldiana Amesoda solida Bithynia tentaculata Dreissena polymorpha Euglesa grassa Euglesa sp. Lymnaea auricularia Neopisidium gr. Moitessierianum Neopisidium sp. Pisidium amnicum Pisidium inflanatum Sphaerium nitidum Sphaerium nucleus Sphaerium rivicola Unio pictorum Unionidae sp. Valvata depressa Viviparus viviparus Total
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Table 3. Water quality and the percentage of morphological abnormalities in chironomid larvae at the sampling sites in the Cheboksary Reservoir (the first number is the index; the second number is quality: vd–very dirty; d– dirty; p–polluted; mp– moderately polluted) Water quality index Woodiwiss Index Shannon Index Saprobity
402
403
404
405
406
409
410
411
412
413
414
418
420
421
424
426
1
2
2
2
2
4
2
2
2
6
2
2
2
2
2
2
vd
d
d
d
d
p
d
d
d
mp
d
d
d
d
d
d
3.03 2.93 3.29 3.52 1.86 2.67 3.05 2.92 2.13 d
p
d
d
p
p
d
p
p
2.5 p
2.47 2.94 p
p
2.1 p
3.13 3.58 3.29 3.43 3.32 1.63 3.17 3.21 3.88 3.52 2.61 2.91 2.85
1.37 1.87 3.19 p 3.9
p
d
2.97 2.53
p
d
p
p
p
mp
p
p
d
d
p
p
p
d
p
p
P*
7.7
5
15
0
7
10
4.3
9.5
13
9.5
0
0
19
20
11
1.6
P for C. plumosus
50
9
27
0
15
40
33
44
17
29
0
0
33
26
33
3.1
* Share of larvae with abonormalities, in per cent of the total number of larvae
ties reached 20% of the total larvae populations and up to 50% of Chironomus larvae (Table 3). The obtained results testify to the fact that the environmental state of near-bottom water layers in the sites, where the number of chironomid larvae with deformities exceeds 8% (Stations 404, 409, 411, 412, 413, 420, 421, and 424), is critical, in spite of satisfactory values of other water quality parameters (Table 3). In the opinion of different authors [14, 15, 22, 26], the upper limit of the background level of deformities in natural populations of chironomids is 8%. To describe the environmental state of the investigated profiles of the reservoir, the prevailing type of deformities was also studied. Among the revealed types of deformities (mentum gaps, absence of one or several mentum teeth, absence of one or several mandible teeth, abnormalities in epipharengial pecten, pigmentation, and abrasion abnormalities), mentum gaps (Kohn gaps, according to international terminology [18]), which are regarded as a marker of increased heavy metal concentrations in the bottom sediment [20, 21], are most frequently observed [20, 21]. CONCLUSIONS Results of bottom biocenoses investigation in the Cheboksary Reservoir give us an idea of the general environmental state of this water body. Increased level of morphological abnormalities in chironomid larvae regarded as a sublethal response of hydrobionts to the effect of negative abiotic factors (toxic substances input, unfavorable oxygen regime, eutrophication of near-bottom water layers, etc.) testify to negative changes in the biotic component of aquatic ecosystems. Biological screening is an important component of the system of environmental monitoring of the Cheboksary Reservoir, aimed at studying the present-day state of WATER RESOURCES
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this water body and forecasting its changes under the increasing anthropogenic load. REFERENCES 1. Alisov, B.P., Klimat SSSR (Climate of the USSR), Moscow: MGU, 1956. 2. Volga i Ee Zhizn’ (The Volga and Its Life), Leningrad: Nauka, 1978. 3. Vudiviss, F.S., Nauchnye osnovy kontrolya kachestva poverkhnostnykh vod po gidrobiologicheskim pokazatelyam (Scientific Principles of Surface Water Quality Control by Hydrobiological Characteristics), Leningrad: Gidrometeoizdat, 1977. 4. Zenkevich, L.A. and Brotskaya, V.A., Materials on the Ecology of the Governing Forms of Benthos in the Barents Sea, Uch. Zap. Mos. Gos. Univ., 1937, no. 13, pp. 203–225. 5. Metody biologicheskogo analiza vod (Methods of Biological Analysis of Water), Leningrad: ZIN Akad. Nauk SSSR, 1976. 6. Nazarova, L.B., Latypova, V.Z., and Tukhvatullina, L.G., Teratogenic Action of Copper on Chironomid Larvae, Toksikol. Vestnik, 1999, no. 3, pp. 30–36. 7. Nachal’nye etapy formirovaniya fauny Cheboksarskogo vodokhranilishcha i ego vliyanie na nizheraspolozhennye uchastki (Initial Stages of Fauna Formation in the Cheboksary Reservoir and Its Effect on the Downstream River Reaches), Kazan: Kazanskii Univ., 1986. 8. Pankratova, V.Ya., Lichinki i kukolki komarov podsemeistva Orthocladiinae fauny SSSR (Diptera, Chironomidae-Tendipedidae) (Larvae and Pupae of Gnats of Orthocladiinae Family of the USSR Fauna (Diptera, Chironomidae-Tendipedidae)), Leningrad: Nauka, 1970. 9. Pankratova, V.Ya., Lichinki i kukolki komarov podsemeistva Podonominae i Tanypodinae fauny SSSR (Diptera, Chironomidae-Tendipedidae) (Larvae and Pupae of Gnats of Podonominae i Tanypodinae Family of the USSR Fauna (Diptera, Chironomidae-Tendipedidae)), Leningrad: Nauka, 1977.
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10. Pankratova, V.Ya., Lichinki i kukolki komarov podsemeistva Chironominae fauny SSSR (Diptera, Chironomidae-Tendipedidae) (Larvae and Pupae of Gnats of Chironominae Family of the USSR Fauna (Diptera, Chironomidae-Tendipedidae)), Leningrad: Nauka, 1983. 11. Ryabov, F.P., Dyga, A.K., Kirilenko, A.S., et al., Samoochishchenie i bioindikatsiya zagryaznennykh vod (Self-Purification and Bioindication of Polluted Water), Moscow: Nauka, 1980. 12. Fauna reki Volgi v zone zatopleniya Cheboksarskoi GES (Volga Fauna in the Zone Flooded by the Cheboksary HPP), Kazan: Kazanskii Univ., 1980. 13. Cranston, P.S. and Reiss, F., The Larvae of Chironomidae (Diptera) of the Holarctic Region—Key to Subfamilies, Entomol. Scand., 1983, Suppl. 19, pp. 11–15. 14. Dermott, R.M., Deformities in Larval Procladius Spp. and Dominant Chironomini From St.-Claire River, Hydrobiologia, 1991, vol. 219, pp. 171–185. 15. Dickman, M., Brindle, I., and Benson, M., Evidence of Teratogens in Sediments of the Niagara River Watershed as Reflected by Chironomid (Diptera, Chironomidae) Deformities, J. Great Lakes Res., 1992, vol. 18, no. 3, pp. 467–480. 16. Hamilton, A.L. and Saether, O.A., The Occurance of Characteristic Deformities in the Chironomid Larvae of Several Canadian Lakes, Can. Entomologist, 1971, vol. 103, pp. 363–368. 17. Hirvenoja, M., Revision Der Gattung Cricotopus Van Der Wulp Und Ihrer Werwandten (Diptera, Chironomidae), Annales Zoologici Fennici. Sosietas Biologica Fennica Vanamo, Helsinki, 1973, vol. 10, no. 1.
18. Kohn T, Frank C. Chironomodae. Ecology, Systematics, Cytology and Physiology, Murray, D.A., Ed., Oxford: Pergamon, 1980. 19. Nazarova, L., Effect of Main Pollutants of Oil-Extracting Region on Incidence of Mentum Deformities in Chironomidae (Diptera) Larvae, Proc. 13-th Int. Symp. Chironomidae. Freiburg, 1997, pp. 87–92. 20. Nazarova, L., A point of view on chironomid deformities investigation, Chironomus, Newsletter Chironomid Res., 2000. no. 13, pp. 7–8. 21. Vermeulen, A.C., Elaboration Chironomid Deformities as Bioindicators of Toxic Sediment Stress: the Potential Application of Mixture Toxicity Concepts, Ann. Zool. Fennici, 1995, vol. 32, pp. 265–285. 22. Warwick, W.F., Morphological Abnormalities in Chironomidae (Diptera) Larvae as Measures of Toxic Stress in Freshwater Ecosystems: Indexing Antennal Defornities in Chironomus Meigen, Can. J. Fish. Aquatic Sci., 1985, no. 42, pp. 1881–1914. 23. Warwick, W.F., Morphological Deformities in Chironomidae (Diptera) Larvae as Biological Indicators of Toxic Stress, Toxic Contaminants and Ecosystem Health; A Great Lakes Focus, New York: Wiley, 1988, pp. 281– 320. 24. Warwick, W.F., Chironomidae (Diptera) Responses to Contaminants in the St. Lawrence River, Environ. Contamination, 4-Th Int. Conf., Ed. Barcelo J. Edinburgh, UK, 1990, pp. 525–528. 25. Wiederholm, T., Chironomidae of the Holarctic Region. Keys to Diagnosis. Mortala, 1983. 26. Wiederholm, T., Incidence of Deformed Chironomid Larvae (Diptera, Chironomidae) In Swedish Lakes, Hydrobiologia, 1984, vol. 109, no. 3, pp. 243–249.
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