Hydrobiologia 239 : 43-52, 1992 .(D 1992 Kluwer Academic Publishers . Printed in Belgium .

Spread of Elodea canadensis in Lake Baikal

0 . M. Kozhova & L. A. IzhboldinaScientific Research Institute of Biology, Irkutsk State University, 664003 Irkutsk, Russia

Received 28 May 1991 ; in revised form 22 October 1991 ; accepted 23 October 1991

Abstract

In Lake Baikal Elodea canadensis Michx . was first observed at the end of the 1970's .Suggestions have been made as to the bringing of E. canadensis to Baikal by aquarists or by trans-

port vehicles and transport together with fishes taken from lakes of the Urals where mass developmentof the plant was observed at the beginning of the present century . The spread ofE. canadensis along LakeBaikal must be due to navigation, but natural factors also affect its spread .

The quantitative biomass development of E. canadensis in various areas of the lake is reviewed, anddiscussed in relation to historical aspects of spread and regulation by environmental factors .

The fast spread of E. canadensis, its high competitive quality and metabolic capacities for purifyingsewage waters deserve attention .Expansion of E. canadensis may be referred to as a catastrophic phenomenon. Its effect has now

covered practically the whole perimeter of Lake Baikal .

Introduction

Between the mid-1970's and early-1980's our at-tention was drawn to the appearance of Elodeacanadensis Michx. first in the River Angara andits reservoirs, then in Lake Baikal . This phe-nomenon needs investigation on the followinggrounds: first, there is a big ecological spread ofthis species on the Euro-Asian continent, it is amajor anthropogenic factor able to cause changesin the unique ecosystem of Lake Baikal ; third, itis a possible agent of water self-purification .

The traditional habitat of Elodea canadensiswas North America, from which it was broughtto England . During less than two centuries itspread in Europe . Also, it was found in the lakesof the Urals .

Historical aspects of spread in Baikal

Elodea canadensis seemed to appear in the IrkutskReservoir (filled in 1956) after 1959, as in 1956-

43

59) when Kozhova investigated plant periphytonit was not observed . In 1974 it expanded its hab-itat vigorously . Between the Irkutsk and Bratskreservoirs the abundant development of Elodeacanadensis was described in 1976, when it wasestablished that Elodea canadensis and otheraquatic plants (Cladophora spp., Myriophyllumspp., Potamogeton spp.) clogged up the gratings ofwater intake arrangements in the region of thetown of Angarsk .

The abundant growth of these plants was ob-served in small lakes on the shores of the Angarariver and particularly in a special channel alongthe shore of Angarsk, where the temperature ofthe water was some 3-4 °C higher than in theAngara River. Evidently, this factor has contrib-uted to the development ofElodea canadensis andother plants (Kozhova et al., 1985) .

In Bratsk Reservoir, where plant periphytonwas examined 1962-1967 (Kozhova, 1970),Elodea canadensis occurred neither in the flowingpart of the reservoir nor in its bays . But in 1974

44

floating fragments of its stem occurred in mass,not only along navigable waterways but also inthe upper part of the reservoir .

This is an indication of the probable spread ofElodea canadensis both in the Bratsk Reservoirand in lower-located reservoirs . In Lake BaikalElodea canadensis was first observed at the end ofthe '70s in the Selenga River shallows (Neronov& Maistrenko, 1981) .

There are several assumptions regarding theways of penetration of Elodea canadensis intoLake Baikal . One of them is an expansion bydifferent ways from the Irkutsk Reservoir, whereits mass growth was observed earlier than in thelake (1974) (Neronov & Maistrenko, 1981) . Thesecond source might be the Selenga River, asstated by Neronov & Maistrenko . But in 1972-3 Pautova (1973, 1974) investigated the Selengashoal of Lake Baikal and did not observe Elodeacanadensis in the Selenga River delta . Hence,Elodea canadensis appeared - at least in mass -after 1973, most probably in 1974-1977(Kozhova & Timofeeva, 1986), as at the end ofthe '70s it was discovered there in mass .

To explain the above, assumptions have beenmade as to the bringing of Elodea canadensis toBaikal by aquarists (through they use anotherspecies of Elodea) or by transport vehicles, andone more way may be added - transport ofElodeacanadensis together with fishes which were takenfrom the lakes of the Urals, where mass devel-opment of the plant was observed at the begin-ning of the present century .

After comparison of all dates concerning thediscovery of Elodea canadensis in Lake Baikaland River Angara, it is evident it has happenedalmost simultaneously - in the middle of the '70s .It suggests that the appearance of the plant inthese waters has occurred by `natural' ways, as inEurope .

After Elodea canadensis was observed in theSelenga shallows, it was found in the southernpart of the Maloye More strait, in Posolsky Sor(a shallow lagoon), and in the Chivyrkuisky Bay(Azovsky et al., 1983 ; Kuzmich et al ., 1985). In1981 it formed closed communities with completecover of the bottom in the southern part of the

Maloye More strait, the Mukhor and Sarminshallow bays. In 1982-3 it existed in many baysof the Maloye More (Khuzhir - Nugo, Kurkut,Bazar, Tutay, Zagly) . It was found not only inundistributed bays that deeply indent the coastand in Mukhor, but in a shoreline zone near capes .The phytomass (fresh weight) of Elodeacanadensis reached 2-5 kg m-2 in July-August(Kozhova & Timofeeva, 1986) . Elodea canadensisco-occurs with typical plants for this region .

Environmental control of biomass development

As is well-known for the shoreline zone, shallowbays and streams of Baikal are relatively warmand protected from wave disturbances ; theirvegetation is rather diverse and includes widelyspread species of aquatic plants . The most fre-quent are communities dominated by Potamo-geton perfoliatus (Meyer, 1930 ; Kozhov, 1931,1947; Kozhov & Spelit, 1958 ; Pautova, 1974;Azovsky et al ., 1983). In such regions endemicalgae of Baikal - that constitute the main part ofthe flora - are absent, but during summer suchwidely spread genera as Cladophora, Spirogyra,Oedogonium, and Mougeotia are abundant . Insome places Elodea canadensis develops as sep-arate growths, with other plants absent . This is anindication that it inhibited the Potamogeton spp .communities, spread in the southern part ofthe Maloye More strait (Kozhova et al ., 1986) .Neronov & Maistrenko (1981) pointed out theinhibitory effect of Elodea canadensis on localspecies of higher waterplants in Posolsky Sor,though in the '80s it grew under the cover ofPotamogeton spp . Sometime later it appearedalong open coasts of the lake, where watervegetation is slow to develop and includes main-ly Potamogeton pectinatus, P . perfoliatus, Ranun-culus trichophyllum, and Myriophyllum spicatum(Kuzmich et al ., 1985). Bottom algae are the mainphytomass in the flora .

On the south-east coast Elodea canadensiswas found in the regions of Utulik settlement(Kozhova & Timofeeva, 1986), Kluevka station,and on the north-west coast of south Baikal be-

tween the Bolshiye Koty river mouth and Zhilishestream (Izhboldinaet al., 1984 ; Zueva, 1987) . Theroots that serve to fix plants in the surf zone makeit possible for Elodea canadensis to grow in openparts of the lake . Its present distribution alongLake Baikal is shown on Fig . 1 . As can be seen,it spreads in deep-cut shallow bays, includingharbours for ships, where its phytomass can reachseveral kg m - 2 , and the weighted-mean phyto-mass is 200-300 g m -2 .The process of spreading Elodea canadensis

from shallow closed parts into more open ones

Fig . 1 . Scheme of Elodea canadensis distribution in LakeBaikal . •, Points of discovery ; o, points free of Elodeacanadensis.

45

has been studied at the Bolshiye Koty settlement(south-west coast of Baikal) . At the beginning ofthe '80s it was found here at the biological stationpier. In 1983 thinned growths were observed be-yond the pier at a depth of 3-6 m on silted sand,where it grew together with charophyte algae . Itsphytomass at the pier reached 200 gm-2 and be-yond the pier on the open place 24 g M-2 . In 1986it was found in this region over a depth range of1 to 16 m . The height of its shoots reached 20-25 cm, the area of growth 0 .5 ha and the meanphytomass 260 g m -2 (Zueva, 1987) . In 1989-1990, according to Gombraih, a thin growth ofElodea canadensis made its appearance on thesites between Chernaya ravine (3 km south of theBolshiye Koty settlement) and the Kadilny cape(12 km north of Bolshiye Koty). E. canadensis isnow growing in the littoral zone, on silted sandusually devoid of higher water plants (Fig . 2) . Buton the sites of the coasts protected by capes, onsilt or silted sand alongside typical macrophytes(Azovsky et al., 1983 ; Izhboldina et al., 1984), itforms heavy growths (Fig . 3) . In those placeswhere on stones branched forms of Baikal sponge(Lubomirskia baicalensis Dyb.) occur, the shootsof Elodea canadensis entwine the sponge . Thus,Elodea canadensis assimilates these typical Baikalbiotopes. The negative response of Baikal spongeto Elodea canadensis has not been directlyrecorded, but, supposedly, it does exist, at leastdue to insufficient quantity of light for the photo-synthesizing zoochlorellae responsible for thegreen colour of the sponge. More frequentlyElodea canadensis occurs along the west coast ofthe lake (Fig. 1) .

In 1984-1986 special quantitative estimates ofElodea were made in the places of its mass growth(Posolsky Sor, Olkhonsky Gates strait, southernpart of the Maloye More strait) . Besides deter-mining the borders of its distribution, an exami-nation of the whole coast of the lake was carriedout in July-August 1988 (Fig. 1). The sampleswere collected in summer using a dredge (area0 .025 m2), but also in the regions with abundantElodea canadensis by aqualung divers aided by aspecial diving bell with 0 .25 m2 inlet. The diversselected samples, and determined the distribution

46

Fig . 2 . Along the open shallows of Lake Baikal Elodea canadensis inhabits silted sands devoid of higher plants .

and degree of cover of the bottom, average heightand viability of the plants. The samples were fixedwith formalin. The weight of the algae was laterdetermined in the laboratory. The surface mois-ture was removed on filter paper; 400 quantitativesamples were analyzed . The annual production(P) of Elodea canadensis has been calculatedby the formula proposed by Raspopov (1973) :P = 1 .2 B, where B is the maximum overgroundphytomass .

To determine the production of Elodea cana-densis quantative estimates were made in Posol-sky Sor in June 1984, i .e. at the beginning ofvegetation, and in September, in the period ofmaximum phytomass . In July Elodea canadensiswas observed on silt and silted sand in the cen-tral part of the coast along spits separating thecoast from the open Baikal (Fig . 4) . It co-occurredwith macrophytes typical of this region . Theheight of the branches of Elodea canadensis andPotamogeton perfoliatus did not exceed 10-15 cm

in June, but in central deeper parts of the coast,on viscous grey silt with a large admixture oforganic material, the height of juvenile brancheswas greater and reached 20-25 cm . The phyto-mass (fresh weight) of Elodea canadensis in dif-ferent parts of the coast varied from 0 .2 to68 gm-2. The weighted mean value was15 .6 g m -2 , which implies 166 tons fresh (air-wet) weight or 27 .7 tons of dry substance or 10tons of carbon per unit area (1063 .8 ha). In Sep-tember the height of branches was greater andreached 60 cm. In different parts of the coast thephytomass varied from 0 .9 to 437 gm-2. Theweighted mean value was 40 g m -2 , i .e . 2 .5 timeshigher than in June . Thus, seasonal changes in theincrease of biomass are due to the growth ofbranches ; their length, like the mean phytomass,increased from June (to 20-25 cm) to September(60 cm) by 2.5 times . The total weight of Elodeacanadensis in Polsolky Sor was 425 .4 tons, withestimated annual production of 510 tons of air-

Fig. 3 . Elodea canadensis and Potamogeton perfoliatus growing in a shallow place well protected from waves .

wet weight, which corresponds to 71 tons of ab-solute dry weight or 25 .7 tons of carbon (Figs . 4,5, 6) .Analysing the spread of Elodea canadensis

in Lake Baikal, in the years of its discovery,Kozhova & Timofeeva (1986) have suggestedthat in future there is a possibility or cardinalchange of the vegetation of the coastal-sor zoneof Baikal where the conditions most favourthis plant. In this connection it is of interest tocompare data on distribution and intensity ofvegetation of Elodea canadensis in Posolky Sor,where its mass development, preventing fish fromspawning, was observed in 1981 . In September1989 the growths of Elodea canadensis couldhardly have prevented fish from spawning. More-over it is difficult to believe that the species hadan inhibitory effect on the common plants of thesor .

Elodea canadensis grew under the cover ofPotamogeton perfoliatus, the height of whichreached 3-4 m . Kuzmich et al. (1985) note that

47

the phytomass of Potamogeton sp . was twicegreater than that of Elodea canadensis, and itsphytomass (fresh weight) was 700 g m - 2 . Evi-dently in 1984 there was a decline in the devel-opment of Elodea canadensis in Posolky Sor, ascompared with data from the late '70s to early'80s. However the difference in the data obtainedin September 1984 and by Kuzmich may be dueto interannual changes of biomass typical ofBaikal, which are affected by fluctuations of thewater level and upwelling of the river . Also, theaverage time for mass development of Elodeacanadensis in European reservoirs is 40 years,and in the lakes of the Urals 22 years (Mishin &Gribovskaya, 1960). It is hard to believe thatduration of mass development in the region of theBaikal basin can be much shorter .

The spread of Elodea canadensis in the Olkhon-sky Gates strait and in the southern part of theMaloye More strait was studied in July 1984, inAugust 1985 and in 1986. In July 1984 heavygrowths of the plant were found in interior parts

48

A

A.f

Nuu~y~ u

t

+i .

III

~~~~Illlllqu~~~, T III I(l-I

of the Khuzhir-Nugo and Shide bays, where com-plete bottom cover was 100 %, and mean phyto-mass 1800 and 4260 g M-2 respectively (Fig . 5) .In such communities of Elodea canadensis otherhigher water plants are absent or grow under thecover of the Elodea canadensis, the height of whichreaches 1-1 .5 m . Algae typical of these regions inassociation with the dominant Elodea canadensisare constant species (occurrence 50%), but theirrole in the total phytomass is extremely low . Along

Ha- 3

12

Fig . 4 . Distribution of sediments and plants according to Kozhova & Spelit (1958) (A) and of Elodea canadensis phytomass (B

- June 1984, C - September 1984) in the Posolsky Sor . 1 - isobaths, 2 - sands, 3 - silted sands, 4 - silts, 5 - Potamogeton

perfoliatus, Myriophyllum sp ., Ceratophyllum sp ., 6 - Carex sp., 7 - Polygonum sp ., Sparganium sp ., Nuphar sp . ; B, C fresh (wet)

weight of Elodea canadensis (g m -2 ) : 8 - 0.1-10, 9 - 10-100, 10 - 100-1000, 11 - transects .

-1

-SM _/0

shores of the Olkhonsky Gates strait the growthsof Elodea canadensis have been examined fromthe Mukhor bay to Jubuhan capes, where its phy-tomass did not exceed 10 g m -2 . On the shoresof the Olkhonsky strait thin growths were ob-served only in the regions of an old pier, in theinner part of the Zagly bay . The total area ofElodea canadensis in this region of Baikal in Julywas 963 ha, with a phytomass of 2894 tons whichcorresponds to 474 tons dry weight and 172 tons

®-1, ®-2, -3,--4

Fig . 5 . Scheme of the distribution of Elodea canadensis in the Olkhonsky Gates strait and southern part of Maloye More straitin July (A) and in August (B) 1985 . Fresh weight ofElodea canadensis (g m -2 ) : 1 - 1-10, 2 - 10-100, 3 - 100-1000, 4 - > 1000 .

of carbon (Table 1) . More than half of thearea (56%) was occupied by Elodea canadensiswith phytomass from 10 to 100 g m - 2 . Theweighted mean phytomass on the whole areawas 294 g M-2, i .e . 7.5 times greater than in thePosolsky shore lake. In August 1985 furtherspread of Elodea canadensis at the OlkhonskyGates strait was observed. It was met east of the

Table 1 . Area occupied and phytomass of Elodea canadensis in different sites of Lake Baikal .

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Jubukhan cape in a small bay . On the Olkhonskyshore it was found in the Perevozhnaya bay . Thereis a passenger ferry between these capes due towhich, probably, it was brought to Olkhonskyshores .

In Maloye More strait Elodea canadensis con-tinued to take over new habitats . In the southernpart of the Maloye More its communities were

Month,year

Generalarea, ha

Generalphytomass t

Areas with phytomassdensity (g m -2 ) per cent

Average phytomassdensity (g m

_2 )

freshwt

dry

Cwt

0.1- 10- 100- freshwt

drywt

C

In Posolsky Sor

June 1984 1064 166 28 10 35,1 64,9 - 15,6 2,5 0,9September 1984 1064 426 66 25 45,4 42,9 11,7 40,6 6,7 2,4

In Olkhonsky Gates and Moloye More straits

June 1984 963 2840 474

172 31,6 47,0 14,7 294,0 49,0 17,7August 1985 1261 3795 634

230 29,1 56,4 9,8 300,0 50,1 18,1August 1986 1189 3344 558

202 29,9 34,9 25,6 281,0 46,9 16,9

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found except for Khuzhir-Nugo and Shide bays,is a small bay at Antukhai cape, where its phy-tomass was 1150 gm-2 . The total area of Elodeacanadensis in August 1985 as compared with thatin July had increased from 963 ha to 1260 ha, andthe air-wet phytomass was 3794 tons (229 .3 tonsof carbon) (Table 1) .

In August 1986 along the shoreline in theOlkhonsky Gates strait the development of Elo-dea canadensis, as in previous years in Kurkutskybay and at Shibete cape (1724 g m -2), had be-come more massive (1575 and 1724 g M-2 re-spectively), and in individual samples the weightreached 10600 gm-2. The area of Elodea cana-densis had increased with phytomass density from100 to 1000 g m - 2 . A movement of Elodeacanadensis towards open Baikal to Oboin cape isbeing observed .

In the Maloye More strait the spread of Elodeacanadensis has been examined along the shoreline

. Sh1betefeskaya

Fig . 6. Scheme of the distribution of Elodea canadensis in the Olkhonsky Gates strait and southern part of Maloye More straitin August 1986 . Symbols as in Fig . 5 .

north to Kurminsk gulf, where detached floatingbranches were found. Along the Olkhonsky shoreof the Maloye More strait it was observed at LakeUgungoi and in the region of the Shibeteisky bay .The total area in both straits was, in August 1986,1189 ha, and the phytomass 3344g (air-wetweight) M-2 . The weighted mean phytomass was280-300 g M-2 in 1984-1986, much higher thanin Posolky Sor (40 gm-2), and can be comparedwith that along the open coast of Lake Baikal atthe Bolshiye Koty settlement .

Discussion

The above is an indication of a wide spread ofElodea canadensis in Baikal. The communities ofElodea canadensis with complete bottom coverare dense, in general, in harbours and in shallowbays and sors, where it co-occurs with widely

spread higher water plants and algae . In the ev-olutionary process these plants could not becomeadapted to the conditions typical for open coastsof the lake, and at present occupy the zones freefrom endemic species of algae (Azovsky et al.,1982). Elodea canadensis is a recent inhabitantand its ecological niche has not yet been deter-mined. Taking these features into consideration,it may be supposed that for some time the abun-dant growth of the plant will take place in shal-low bays. The spread of thin stands is quite pos-sible along the open coasts of Baikal - this isconfirmed by the observations at the BolshiyeKoty settlement. According to the map of distri-bution its outer border is limited by the 5 m iso-bath, though in the open Baikal at the BolshiyeKoty settlement Elodea canadensis is observeddown to 16 m depth . The outer border of its dis-tribution appears to be determined by the trans-parency, as it is known to be sensitive to light, andaccording to Mishin & Gribovskaya (1960) itspreads to the depth close to double the trans-parency determined by Secchi disk . Likewise tosuch depth plant periphyton spreads, as reportedby Kozhova for the Bratsk and Irkutsk reser-voirs . Elodea canadensis is not observed at thevery edge of the water . In the Maloye More straitit appears at a depth of 2 m, in Posolsky Sor 1 m,and in the harbour at the Bolshiye Koty settle-ment . It inhabits both silt and sand bottoms, in-cluding those with a great quantity of organicsubstance (centre of Posolsky Sor), and stonyones that are the habitat of Baikal sponge . Itco-occurs with Potamogeton perfoliatus and otherhigher plants and algae .

Elodea canadensis has a high competitive qual-ity. It can survive frozen in ice, and prefers wa-ters with a low mineral content and high trans-parency. It can accumulate and metabolise toxicsubstances, and is highly toxic-resistant, e .g. tophenolic compounds . It contains $-cyanoalaninesynthetase, the substrates of which are mercaptocombinations particularly methyl-, ethyl-, andbutyl-mercaptans. When using mercaptoethanolas substrate, Elodea canadensis can eliminate itat the rate of 3 mol min - ' mg -1 of plant pro-tein. With high natural density (air-wet weight

5 1

5 kg m - Z) and protein content up to 6 % dryweight, it can become a powerful agent of puri-fying mercapto compounds . The same is true ofthe phenols (Kozhova et al., 1985 ; Kozhova &Timofeeva, 1986) .The spread of Elodea canadensis along Lake

Baikal must be due to navigation, which is con-firmed by the above description of the regularitiesof its distribution in the Olkhonsky Gates strait .However natural factors, streams in particular,affect its spread . In late summer at the west coastits branches were met in the thickness of watertogether with other objects, indicating the SelengaRiver current .

When making a prognosis as to changes of theecosystem of Lake Baikal, the fast spread ofElodea canadensis, its high competitive quality,and metabolic capacities for purifying sewage wa-ters should be taken into account . The intrusionof this plant into Baikal is an example of an un-foreseen effect of eutrophication of the lake, withdeviation from the `normal' functioning of conti-nental aquatic communities . Such expansion maybe referred to as a catastrophic phenomenon,which had not been anticipated, though its effecthas now covered practically the whole perimeterof Lake Baikal .

References

Azovsky, M . G ., V . N . Pautova & S . S . Timofeeva, 1982 . Tothe distribution of Elodea canadensis Michx . in Lake Baikal .In Problemy ekologii Pribaikalya Irkutsk Vol . 2: 63-64 (inRussian) .

Azovsky, M . G ., V . N . Pautova & L . A . Izhboldina, 1983 . Onthe hydrophyte flora of Lake Baikal . Bot . Zhurn . 10 : 1392-1397 (in Russian) .

Izhboldina, L . A ., V . M. Maximova, V . I . Semeykin & V. A .Gombraih, 1984 . The state of macrophytobenthos nearBolshiye Koty (South Baikal) according to data of 1982-1983. Irkutsk, 20 pp. (VINITI N 1804 - 85 Dep .) (in Rus-sian) .

Kozhov, M. M., 1931 . Concerning the fauna of Lake Baikal,its distribution and living conditions . Izv . Biol .-Geogr . Inst .Irkutsk Univ . 5 (1) : 170 pp . (in Russian) .

Kozhov, M. M., 1947 . Fauna of Lake Baikal .-Irkutsk . 297 pp .(in Russian) .

Kozhov, M . M. & K. K . Spelit (eds), 1958 . Fishes and fish-eries in the Lake Baikal basin . Irkutsk . 591 pp . (in Rus-sian) .

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Kozhova, O . M., 1970 . Phytoplankton and hydrobiologicalstate forming of reservoirs of Baikal-Angara. Karkov .57 pp. (in Russian) .

Kozhova, O . M ., V . V. Pautova & S . S . Timofeeva, 1985 .Canadian elodea in Lake Baikal Gidrobiol . Zhurn . 20 : 82-84 (in Russian) .

Kozhova, O . M. & S . S . Timofeeva, 1986 . Role and place ofCanadian elodea in the Baikal ecosystem . Vod. Res . (1) :177-178 (in Russian) .

Kuzmich, V . N ., L . . Moiseeva, A. N. Bystrova & I . G . Ship-ilova, 1985 . Productivity of Canadian elodea in the Posol-sky Sor of Lake Baikal . Krugovorot veschestva i energii vvodoemah . Irkutsk : 52-54 (in Russian) .

Meyer, K . I ., 1930 . Introduction to the algal of Lake Baikal .Bull. Mosk . Obsch . Isp . Prir. 39 : 396 pp . (in Russian).

Mishin, G . M. & I . F . Gribovskaya, 1960. Ecology elodea(Elodea canadensis) in the lakes of the Urals . Biol . nauki .(8) : 72-76. (in Russian) .

Neronov, Yu. V . & S. G . Maistrenko, 1981 . Concerning theproblem `Canadian elodea in Lake Baikal . In Krugovorotveschestva i energii v vodoemah . Irkutsk : 97-99 (in Rus-sian) .

Pautova, V . N ., 1973 . Higher aquatic plants in the shallowwaters of Lake Baikal . In Krugovorot veschestva i energiiv vodoemah . Irkutsk : 142-143 (in Russian) .

Pautova, V. N., 1974 . Higher aquatic plants of Lake Baikal.In produktivnost Baikala i antropogennye izmenenia egoprirody . Irkutsk : 17-26 (in Russian) .

Raspopov, I. M., 1973 . Phytomass and production of mac-rophytes of Lake Onega . In Mikrobiologia i pervichnayaprodukcia Onegskogo ozera . Leningrad : 123-142 (in Rus-sian).

Zueva, N . I ., 1987 . Distribution of Elodea canadensis nearBolshiye Koty (Southern Baikal) . Tez. dokl . konf. mol .uchenykh . Irkutsk : 34 (in Russian) .