current ecological state of the volkhov bay of the … al_2000_ladoga...m.a. naumenko et al. /...

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Current ecological state of the Volkhov Bay of the Ladoga Lake.

M.A. Naumenko, V.A. Avinsky, M.A. Barbashova, V.V. Guzivaty, S.G. Karetnikov,L.L. Kapustina, G.I. Letanskaya, G.F. Raspletina, I.M. Raspopov, M.A. Rychkova,

T.D. Slepukhina, and O.A. Chernykh

Institute of Limnology, Russian Academy of Sciences, St. Petersburg, Russia

(Accepted for publication January 25, 2000)

AbstractThe Volkhov Bay, the largest estuary bay of Ladoga Lake, is characterized. It is shown that owing to special hydrophysical

conditions (higher water temperature during ise-free period, low water transparency, and intensive sediments transport) the ecologicalstate of the bay differs considerably from that of other coastal parts of the lake. With respect to economical importance, the catchmentarea of the Volkhov Bay, is the most developed territory of the Ladoga basin. As a result of increasing nutrient load, eutrophicationprocesses in the bay are obvious. The effect of the waste waters of industrial enterprises favours additional deterioration of waterquality in the southern part of the Ladoga Lake.

Key words: Ladoga Lake, hydrophysics, bottom sediments, oxygen regime, phosphorus, heavy metals, water pollution, plankton,higher aquatic vegetation, zoobenthos, eutrophication, water quality.

IntroductionThe water quality of the Ladoga Lake undergoes

considerable changes caused by anthropogenic ef-fect. This mainly concerns the coastal zones of res-ervoir. The southern part of the catchment area isthe most economically developed region. It includesthe basins of the Volkhov and Syas rivers flowinginto the Volkhov Bay. Several large enterprises arelocated in the Volkhov River basin, among them the“Kirishi nefteorgsintez” and the “Volkhov alu-minium” company.*) The latter is one of the mainsources of phosphorus discharge into the LadogaLake. The waste waters of the Syas pulp and papermill are also discharged into the Volkhov Bay. Ac-cording to the data of Neva-Ladoga Basin WaterAdministration, in 1997–1998 about 150 millionm3⋅yr–1 of polluted waste water was discharged intothe Volkhov and Syas rivers and directly into theVolkhov Bay. When emergency situations occur,waste waters discharge into the Volkhov Bay and therivers flowing into it can increase many times. The

most serious situation occurred in December 1998when the dam constructed as long ago as in 1928 forsewage collection at the purification works of theSyas pulp and paper mill broke, and unpurified wastewaters in the amount of 700 thousand m3 were dis-charged into the tributary of the Syas River and werespread over the adjoining territory.

The systematic discharge of pollutants into thebay and absence of any guarantee for preventinglarge-scaled emergency discharges made it indispen-sable to organize the monitoring of the Volkhov Bayand rivers flowing into it. To interpret the monitor-ing results and to establish the trends of changes inthe water ecosystem of the bay, a detailed charac-terization of its state during many years is neces-sary. This information has been accumulated as aresult of systematic studies carried out at the VolkhovBay by the Limnological Institute of Russian Acad-emy of Sciences and by several other organizationsduring four decades.

This paper briefly present the most important in-formation about the hydrological, hydrochemical,and hydrobiological features of the Volkhov Bayunder natural conditions and during constant pollut-ants discharge into it.

EcologicalChemistry.St. Petersburg,Russia

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*) During the existence of this enterprise its name changed sev-eral times. We use below the old name, the “Volkhov aluminiumworks”, since in this paper data for 30–40 years are reported. —Editors’s note.

M.A. Naumenko et al. / Ecological Chemistry 9 (2000) 75–87

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Morphometry and hydrophysicsof the Volkhov Bay

The Volkhov Bay is the largest estuary bay of theLadoga Lake (Fig. 1). The most important featureof the bay is the fact that it is open towards the lakeand there are no natural barriers separating it fromthe main reservoir of the lake. The north boundaryof the bay is conventionally taking to be the line be-tween the Cape Voronov on the west and the VolchiiNos promontory in the east [1]. The bay area is 807.8km2 and the water volume is 6.6 km3 which amountsto about one seventh of both the volume and thecoastal zone area of the entire lake limited by the18-meters isobath [2]. An important feature of thebay’s morphometry is the fact that about 53% of thisarea belongs to the littoral zone (the boundary of thelake littoral is the 8-meter isobath) which corre-sponds to 25% of the bay volume. The mean baydepth is 8.1 m. The cross-section area at the bound-ary between the Volkhov Bay and the open lake partis 0.486 km2.

The Volkhov River, one of the largest tributariesof the Ladoga lake, flows into the Volkhov Bay. Itswater catchment area is 80200 km2 and the meanannual water flow rate is 560 m3⋅s–1. The second-large river flowing into the Volkhov Bay, the SyasRiver, has the water catchment area of 7330 km2 andthe mean annual water flow rate of 66 m3⋅s–1. Theswampy part of the catchment area of the VolkhovRiver is 8,9% and that of the Syas River is 16%. Theresidence time of the Vokhov Bay is about 4.5months.

As regards its morphological features, theVolkhov Bay is an open deltaless mouth regionswhere wave activity affect the degree of water mix-ing [3]. Its open character favours the penetration oflake water which mix with the river water in an ap-proximately equal ratio (annual average), thus form-ing the bay water mass [4].

Of particular importance are the spreading of riverwaters and the decreasing of its speed in the openpart, which determine the processes of riversediments accumulation. On the basis of the ap-proach described in ref. [3], it may be concludedthat the distance at which the flow rate of river wa-ter becomes equal to the background value is 3–6km. Hence, the Volkhov water can spread further thatthe eight-meter isobath only due to general lake cir-culation. The cyclonic circulation existing in theLadoga Lake in spring and summer penetrates freelyinto the bay and involves the water of the rivers intoits motion. Therefore, the river water after flowinginto the bay deviates to the east in its further mo-

tion. The calculation of the baroclinic Rossby de-formation radius R [5] shows that for the VolkhovBay Coriolis force predominates, especially in win-ter time (R = 3–4 km).

The area of river water spreading in the lake de-pends not only on discharge volume but also on hy-drodynamic and thermal conditions in the lake. Thegeneral structure of water dynamics in the VolkhovBay is distorted by wind activity over its area. Inwinter the northern wind direction dominates and insummer the southern direction prevails. The meanmonthly wind speed in these directions is 6–9 m⋅s–1.The lower wind speed are observed in July and Au-gust and the maximum speeds in November. Atstrong winds the wind effected phenomena areclearly distinguished.

The direction of currents in the Volkhov Bay pro-foundly effected by wind regime [6]. During southand south-eastern winds, the waters of the Volkhovand Syas rivers are directed towards the Petrokrepostbay, and their effect is recorded at the source of theNeva [7]. However, the degree of river water dilu-tion has not been studied in detail.

The prevailing types of bottom sediments in thebay are sands of various sizes and boulders, although

Fig. 1. Schematic map of the Volkhov Bay of the LadogaLake.


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silty sands and even silts are also encountered. Instormy weather, the bottom depths from which theerosion of bottom sediments begins (wave basis) canreach 11–18 m [8]. Wave current velocity at a depthof 5 m can exceed 0.8 m⋅s–1 [9]. Hence, bottomsediments are influenced by waves over virtually theentire area of the Volkhov Bay.

The study of sediments transport along the shoresmade it possible the establish the zones of erosion,transport, and accumulation of material [10]. Its flowalong the western shore of the Volkhov Bay is di-rected from the south to the north. The focus of itsaccumulation is located between the mouths of theVolkhov and Syas rivers. Along the western bayshore, 22 thousand m3 of sediments are transported

here and 12 thousand m3 along the eastern shore.However, this transport has no great effect on themorphology of the western shore. Simultaneouslythe eastern shore is continuously eroded and the bot-tom slope gradually decreases which is accompa-nied by the retreat of the shore line.

At the north eastern boundary of the bay in theregion of the Volchii Nos and Storozhensky capes,the divergence of wave energy fluxes occurs.Sediments in the amount of 800 thousand m3 aretransported from the erozion zone to the south intothe Volkhov Bay. The eastern shore and the bottomslope in its water boundary area is being continu-ously eroded, whereas at the lower slow parts (lowerthan five meter isobath) deposits are accumulated.

Fig. 2. Average annual (multiyear) distribution of water surface temperature (°C)referred to the middle of the month.


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Observations carried out for establishing the correctlocation of waste water discharge of the Syas pulpand paper mill [11] have shown that solid residuesfrom wood treatment were accumulated mainly tothe east of discharge site.

The Volkhov Bay is one of the warmest bays ofthe Ladoga Lake. Ice destruction starts in April atthe mouth of the Volkhov River and from the side ofopen lake with simultaneous increase in water flowin the river. Fig.2 shows the mean temperature dis-tribution in the bay for many years. In the middle ofMay, the spring thermal frontal zone (thermobar) islocated at its north boundary and prevents the spread-ing the river water to the lake centre. Since at thistime the water of rivers is heated more rapidly than

coastal lake water [12], river water is spread abovelake water.

In June, the bay exhibits the greatest spatial ther-mal inhomogeneity. From July the degree of waterhomogeneity increases, and in August – Septemberwater temperature becomes the same virtuallythroughout the bay.

In summer time, the main role in the formationof the thermal structure of the Volkhov Bay is playedby heat arrival at water surface as well as by windregime. Since the bay is shallow and open, windmixing reaches the bottom at mean wind speed,which leads to destruction of temperature stratifica-tion and to rapid heating or cooling of the water mass(Fig. 3-A). The diurnal course of water temperature

Fig. 3. Average long-term distribution of water temperature of the Volkhov Bay and air temperature over the watersurface: A — vertical distribution of 10 days average water temperature (°C); B — vertical distribution of disper-sion of water temperature (°C2); C — distribution of air temperature for ice-free period.


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reaches the bottom. However, on calm days a con-siderable vertical temperature gradient appears whichprevents heat exchange between surface and bottomlayers. The change in water temperature dispersionwith time (Fig. 3-B) shows that a considerable tem-perature gradient can exist in bottom waters layersin July and August as was reported byJ.V. Molchanov a long time ago [13]. This is due tothe exchange between cold water of the central lakepart and more heated coastal water.

Maximum air temperature over the Volkhov Bayexists at the end of July (Fig. 3-C), and the maxi-mum water surface temperature is observed with acertain delay: in the first decade of August.

The Volkhov Bay is characterized by the lowestwater transparency as compared with other parts ofthe coastal zone of the lake. This is caused by theflowing in of river waters and the stirring up of bot-tom waters. Suspended particles concentration in theVolkhov River in spring can attain 18 g⋅m–1, whichis 2–3 times as much as in the lake centre. Moreo-ver, 30–50% of particles consist of organic matter[14]. Maximum turbidity (and minimum transpar-ency) of water in the bay is observed in May (Fig.4). In this period, water transparency in the bay is60% lower than throughout the other coastal part ofthe lake. After the end of spring, high water and upto October, statistically significant differences be-tween mean monthly water transparency values inthe bay disappear, although transparency remains

lower than in other regions of the coastal lake part.Images made from space show distinctly more

turbid Volkhov-waters (Fig. 5). They can be followedat the wind effected phenomena in the period of openwater (April, May, and June) along the eastern shoreof the bay upper to its boundary.

Hydrochemistry of the Volkhov BayHydrochemical studies in the Volkhov Bay were

carried out from the 1930s to the end of the 1990s[15–21]. The problem of water quality was consid-ered as far back as in 1931 in connection with infe-rior spawning conditions [11].

The hydrochemical regime of the bay is formedunder the influence of several factors. The principalrole is played by river waters. Seasonal water tem-perature distribution and wind activity also producea considerable effect.

The Volkhov and the Syas rivers are character-ized by higher major ions content in water (as com-pared with the main tributaries of the lake). The meanannual value of major ions content in water of theSyas River is 120 mg⋅l–1, and the maximum valueduring winter low water level can attain 300 mg⋅l–1.The same mean annual values for the Volkhov Riverare about 150–160 mg⋅l–1. In low water years therange of major ions content is 90–320 mg⋅l–1 and inhigh water years it is 70–220 mg⋅l–1.

The chemical composition of the water of theVolkhov River differs from that of all other rivers of

Fig. 4. Average monthly transparency (white disk depth), 1958–1998: 1 — average values, 2 —mean-square deviation, 3 — standard error.


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the Ladoga basin. Although this water with respectto the ratio of major ion belongs to hydrocarbon-calcium type, in their anion composition during lowwater level period, chloride ions predominate oversulphate ions, whereas in spring and during rainyhigh water, the contributions of chlorides and sul-phate are equal.

The major ions content of the Volkhov bay watervaries over a wide range: from 170 mg⋅l–1 to valuesclose to the lake values (65 mg⋅l–1). Among the maintributaries the lake, the Volkhov River is distin-guished by high (as compared to the Svir and theVuoksa rivers) phosphorus content and is the mainsource of this element in the lake. These features ofthe river result from the combined effect of phisico-geographical and anthropogenic factors [22,23].

From the beginning of 1970s the Volkhov alu-minium works became the main source of this ele-ment because they began to use nephelines as rawmaterial for production of aluminium. The greatestamount of phosphorus was discharged into the bayfrom the catchment area at the end of 70s and at thebeginning of the 80s (Table 1) [22,25]. In these yearsduring the ice-free period, the maximum total phos-phorus content in the bay water attained 260 µg⋅l–1

at a mean value of 70 µg⋅l–1. In the winter of 1977–1978 in the zone close to the mouth of the VolkhovRiver, concentrations of 360–380 µg⋅l–1 were ob-served [18].

Partial transition of the Volkhov aluminium worksto the system of circulating water supply and thedecrease of production at the works and at the Syas

Fig. 5. Scheme for spreading of the Volkhov River water according to satellite data(LANDSAT, visible range): 1 — April 30, 1975; 2 — May 28, 1978; 3 — June 23, 1973.


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pulp and paper mill favoured a decrease in phospho-rus discharge into the Volkhov Bay. In the 90s theaverage content and the range of total phosphorusconcentration in the bay water decreased almosttwice (Table 2), although local differences remainedconsiderable. Maximum phosphorus concentrationsare charactreristic of coastal parts and the zone ad-joining the mouth of the Volkhov River. The mini-mum values do not exceed concentrations typical ofthe open lake (15–20 µg⋅l–1). Inorganic phosphorusfraction is on the average 13–36% of its total con-tent. Its concentration at some parts during inten-sive photosynthesis of phytoplankton can reduce tovalues below detection limit, although near the mouthof the Volkhov River even in summer concentrationincrease to 80–100 µg⋅l–1 is observed.

Nitrogen discharge into the bay did not changegreatly by the end of the 90s as compared to 1967–1988. A certain tendency to decreasing total nitro-gen content in the bay water appeared. Concentra-tion range has always been smaller than for phos-phorus, and the mean value was close to those char-acteristic of lake water. Nitrates were always presentin the bay water, their average concentration in thesummers of 1994 and 1995 was close to 100 µg⋅l–1,and in the autumn of 1995 it was 190 µg⋅l–1.

Organic matter discharge from the catchment areainto the Volkhov Bay (just as that into the whole lake)depends mainly on water level of the year and remainsrelatively stable for the long-term series [25,26]. Wa-ter colour in the bay ranges from 140 to 25 Pt-units. Inother words, it can exceed three or four times watercolour in central lake part, which is due to the domina-tion of allochtonous organic matter.

Seasonal variations in organic carbon concentra-tions are slight but exceed those for the open lake.

Local variations are determined by spreading of riverand lake water through the bay. The labile compo-nents of organic matter are indirectly indicated byBOD

5 values which seldom exceed 6 mg O

2⋅l–1.

Content of oxygen dissolved in water is mainlydetermined by thermal conditions. However, produc-tion and destruction processes also play an impor-tant role. Relative oxygen content ranges from 65 to125% saturation (Table 2). Water supersaturated withoxygen is accompanied by high pH values, whichindicates that the oxygen maximum is of the photo-synthetic origin. Minimum oxygen content was ob-served in the vicinity of the mouth of the VolkhovRiver and in shallow water near the coast.

The water of the bay is characterized by higherconcentrations of heavy metals than that in the openlake (Table 3) [22]. The reason for relatively highcontent of iron, aluminium, and manganese is thatthe catchment areas of rivers flowing into the bayare rather swampy. The spatial distribution of metalcompounds over the reservoir is very inhomogene-ous. Near the mouth of the Volkhov River, iron, alu-minium, and manganese concentration exceed morethan 1.5–3 times those in the other parts of the bay.Manganese is characterized by the greatest concen-tration variation. In contrast, lead concentrationsthroughout the bay change only slightly. Changes incopper content are mainly caused by the intensity ofphytoplankton development because it accumulatescopper. High copper concentrations are observed inregions far from the mouth of the Volkhov River.Seasonal distribution of metal compounds is usu-ally characterized by high spring concentrations ascompared with summer and autumn values.

Oil hydrocarbons and phenols content in the wa-ter of the bay is most often within the LAC limits

Table 1

Mean annual concentrations of phosphorus and nitrogen in river water andwaste water and discharge of nutrients in the Volkhov Bay

Total phosphorus Total nitrogenSource ofdischarge Years

Concentration,µg⋅l–1

Discharge,t⋅yr–1 Years

Concentration,mg⋅l–1

Discharge,t⋅yr–1

Volkhov 1959–1962 46 760

1976–1982 210 3750 1976–1982 1.18 21200

1991–1998 120 2310 1992–1998 1.14 22600

Syas 1959–1962 24 38

1976–1982 95 200 1976–1982 1.00 2070

1991–1998 80 190 1992–1998 0.84 1830

Syas PPM 1981–1982 2400 180 1981–1982 13.2 990

1997–1998 – 5 1997–1998 60


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(50 and 1 µg⋅l–1, respectively). However, in the re-gion close to the Volkhov mouth, high values of theirconcentrations are sometimes observed, which maybe caused by waste water discharge into the river.Oil hydrocarbons and phenols concentrations in-crease in autumn over those in summer (data of V.A.Shcherbak and N.L. Krylenkova). This may be dueto more intensive destruction processes in summer.

In winter and periodically in summer in calmweather, water stratification can be distinctly ob-served in the bay. It is especially well distinguishedfrom water colour and phosphorus content (Table4). In winter, denser river water is revealed in near-bottom horizons at a distance of 30–35 km from theVolkhov mouth. In contrast, in summer the water ofthis river is spread along the surface, although com-

plete mixing of river and lakes waters in this periodtakes place more rapidly [18]. For many years inJune and especially in July, the region of highhydrocarbonates content indicating the spreading ofthe river Volkhov water in the lake can be followingup to the latitude of the Valaam Island [17,19,20].

Hydrobiological characterization of theVolkhov Bay

Hydrological and hydrochemical features of theVolkhov Bay determine specific properties of itsbiocenosis. Phytoplankton of the bay differs fromthat in other parts of the lake both in the species com-position and the structure of the biomass and func-tional parameters. These differences are retained inall seasons. In spring and autumn, the phytoplanktonis dominated by the Bacillariaphyta. Chlorophyll “a”and the total biomass in the bay isolated by thethermobar are ten times higher than in the centralpart of the lake [27,28]. In summer, these differencesare not so sharp. Nevertheless, the phytoplankton ofthe bay is always richer than that in the main pelagialarea.

The current state of this community is consid-ered on the basis of data of 1992–1997 (August).The phytoplankton is dominated by the Cyanophyta(50% of the total biomass), Cryptophyta (20%),Bacillariophyta (13%), and Chlorophyta (7%). Inthe coastal parts of the bay, species of the Microcystisgenus: M. aeruginosa Kutz. emend Elenk., M.reinboldii (Wood) Forti, M. viridis (A. Braun.)Lemm., and M. wezenbergii (Kamarek) Star. arenumerous. Most of them are toxic. The biomass of

Table 2

Hydrochemical characteristics of the the Volkhov Bay

Spring (V–VI) Summer (VII–VIII) Autumn (IX–X)

ComponentUnits

Years Meanvalue

Range Meanvalue

Range Meanvalue

Range

O2 mg⋅l–1 1988–1998 11.1 9.0–13.0 8.6 6.3–11.0 10.5 6.9–11.6

% 104 94–113 98 65–125 92 83–97

pH 1988–1998 7.75 7.25–8.25 7.65 6.8–8.8 7.45 7.1–7.8

Ptot µg⋅l–1 1988–1998 31 18–88 34 14–120 39 15–140

Pmin µg⋅l–1 1988–1998 4 < 1–12 12 < 1–100 12 2–54

Ntot µg⋅l–1 1988–1998 590 520–680 630 500–820 810 760–900

Corg mg⋅l–1 1988–1998 13.2 5.5–20.4 10.9 6.5–20.4 9.3 6.1–17.6

BOD5 mg O

2⋅l–1 1988–1998 1.9 1.1–2.7 1.5 0.6–2.6 1.0 6.1–17.6

Oilhydrocarbons

µg⋅l–1 1992–1998 – – 44 6–89 56 11–100

Phenols µg⋅l–1 1992–1998 – – 0.9 <0.5–3.6 – 0.1–65

Note: all values are averaged for the volume of the bay water mass.

Table 3

Concentration of heavy metal compoundsin the Volkhov Bay water, µg⋅l–1 (1988–1998)

Bay parts

Near the mouthof the Volkhov River

Far from the mouthof the Volkhov River

Elements

Meanvalue

Limits ofconcentration

changes

Meanvalue

Limits ofconcentration

changes

Fe 278 80–469 172 54–362

Al 109 36–252 52 17–246

Mn 42 3.5–94.5 13.3 2.5–26.7

Cu 6.8 0.4–20.4 10.7 0.9–50.4

Pb 1.5 0.3–5.4 1.3 0.2–5.7


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blue-green algae attained 2–3 g⋅m–3 in some years.These values indicate water “bloom” and deteriora-tion of water quality. In the main part of the bay,species of the Anabaena genus dominated: : A.circinalis Raben., A. flos-aquae Breb., A. spiroidesKleb. and Aphanizomenon flos-aquae (L.) Ralfs. Themain species of Cryptophyta were Cryptomonaserosa Ehr. and Rhodomonas lacustris Pasch. et Rutt.Among diatoms, the most frequent species wereStephanodiscus binderanus (Kutz.) Krieg., St.hantzschii Grun. and Aulacoseira italica (Ehr.) Sim.This situation is due to unstable summer stratifica-tion in the bay, which is often perturbed by windmixing favouring the maintenance of heavy cellsdiatoms in water. The presence of numerous speciesof green algae (Scenedesmus Meyen and PediastrumMeyen) indicate sufficiently high concentrations ofnutrients. The community structure of phytoplanktonshows relatively high trophic state of the bay.

Phytoplankton distribution throughout the bay isvery inhomogeneous. Biomass ranges from 0.5 to6.6 g⋅m–3, chlorophyll “a” content from 4.3 to 15.8mg⋅m–3, and photosynthesis intensity from 120 to471 mg C⋅m–3⋅day–1. Horizontal heterogeneity ofphytoplankton is due to specific features of hydro-dynamic regime of the bay. However, seasonal vari-ations of mean values are not great: the biomassranged from 1.5 to 2.4 g⋅m–3, chlorophyll “a” con-tent from 7.5 to 92 mg⋅m–3, and photosynthesis in-tensity from 240 to 356 mg C⋅m–3⋅day–1, which iswithin the normal value for this community that is

mainly caused by meteorological conditions in ob-servation years. These results indicate that the stateof phytoplankton is stable under present conditions.

According to summer data, the mean values( X± SE) for the biomass were 2.1 ± 0.24 g⋅m–3, forchlorophyll “a” 8.3 ± 0.7 mg⋅m–3, and for photosyn-thesis intensity 312 ± 26 mg C⋅m–3⋅day–1. Accordingto existing classifications of the trophic state forphytoplankton, the bay belongs to true mesotrophictype.

Zooplankton is one of the most important com-munities of the ecosystem ensuring the mineraliza-tion of the autochthonous and allochtonous organicmatter. Its role in phosphorus regeneration and itsinvolvement in biotic circulation is considerable.Moreover, it is the main component of the food ba-sis for planktophagous fish and for all young fish.

The Volkhov Bay is traditionally considered asone of the most productive (for plankton) regions ofthe Ladoga Lake [29]. The most usual mass formsof zooplankton are Asplanchna priodonta (Gosse),Keratella cochlearis (Gosse), Conochilus unicornis(Rousselet), species of genera Polyarthra andSynchaeta — from Rotatoria; Thermocyclopsoithonoides (Sars), Mesocyclops leuckarti (Claus),Eudiaptomus gracilis (Sars), Eurytemora lacustris(Poppe), Daphnia cristata (Sars), Bosminacrassicornis (P.E. Muller), Limnosida frontosa (Sars)— from Crustacea.

All data refer to the period of mass zooplanktondevelopment (July – August) in 1990–1998. The

Table 4

Vertical distribution of water colour andphosphorus content in the Volkhov Bay water

Phosphorus,µg⋅l–1No. of

collection site(see Fig. 1)

Distance fromthe mouth of theVolkhov River,

km

Horizon, mP

totP

min

Water colour,Pt-units

Summer (August 19, 1977)

1 5.5 0.5 140 48 95

6.0 38 1 50

2 7 0.5 215 98 136

6.5 68 14 50

Winter (March 23, 1978)

1 5.5 0.5 44 23 39

6.9 300 240 99

25 ∼ 30 0 40 18 39

10 24 21 39

15 94 51 –

20 266 222 120


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numbers, of net zooplankton for some years rangedfrom 16.4 to 57.4 thousand ind.⋅m–3 and were on theaverage 30.4 (11.7) thousand ind.⋅m–3 (in parenthe-ses here and below — mean square deviation). Thenumbers of Copepoda somewhat exceeded that ofCladocera: 52 and 44%, respectively. The biomassvalues of net zooplankton varied over a wider rangefor several years: 0.35–2.35 g⋅m–3 and were on theaverage 0.90 (0.56) g⋅m–3. However, if two extremevalues were excluded the range became much morenarrow : 0.45–1.04 g⋅m–3. The share of Cladocera inthe biomass greatly exceeded that of Copepoda.: 56and 29%, respectively. This should be considered acharacteristic feature of the Volkhov Bay as com-pared to other lake parts. Accordingly, in some years,the Cladocera (L. frontosa, D. cristata, B.crassicornis), as well as large Rotatoria (A.priodonta) dominated in the biomass.

Considering the bay zooplankton one shouldmention that larvae of Dreissena polymorpha (Pallas)were detected in it (in 1995 and 1998 ) the massspreading of which can lead to important negativeconsequences.

The evaluation of long-term changes in the bayzooplankton is difficult and tentative because the dataare scarce. However, taking into account the data ofthe end of the 1940s [29] one can speak about thecertain stability of net zooplankton development.Unfortunately, the data on its small-size fractionsfor 1947–1949 are absent, and, therefore, it is riskyto draw conclusions about a great increase in num-bers and changes in structure of zooplankton becauseof eutrophycation [30–32]. The general level ofzooplankton development in the bay (according toformal criteria [33,34]) can be considered to be char-acteristic of oligotrophic or weakly mesotrophic res-ervoirs. In some years, at mass Cladocera develop-ment, biomass values can correspond to a highertrophic state.

At the beginning of the 60s, on the backgroundof the general low bacterioplankton concentration[(0.18–0.30)⋅106 cells⋅ml–1), the Volkhov bay intowhich large quantities of suspended particles andnutrients are discharged, was distinguished by rela-tively considerable micro-organisms densities (about0.5⋅106 cells⋅ml–1). Directly at the mouths of theVolkhov and the Syas rivers, even higher bacterialnumbers (1.75⋅106 and 4.2⋅106 cells⋅ml–1, respec-tively) were observed. In the region of the collectorof the Syas pulp and paper mill, the total bacterialnumbers and concentration of saprophytic bacteriaattained tremendous values: 17.6⋅106 and 2.8⋅10 3

cells⋅ml–1, respectively [35,36]. The collector stream

partially spreading in the bay was directed along thenorth-eastern coast, and, very high bacterial abun-dance was detected at a distance of about 6 km andthen decreased to background values (0.35–0.40)⋅106

cells⋅ml–1 [35].In 1994–1998, maximum (for the lake as a whole)

microbiological parameters was observed in the bay.They corresponded to the mesotrophic level withsome features of the eutrophic state. Thus, meansummer values of bacterial density and heterotrophicassimilation of CO

2 in the bay were 2.05⋅106

cells⋅ml–1 and 7.7 µg C⋅l–1⋅day–1, respectively. Themaximum values attained 10.0⋅106 cells⋅ml–1 and28.2 µg C⋅l–1⋅day–1, respectively. In connection withthe euthrophication of the Ladoga Lake, the abso-lute values of microbiologiacal parameters in the bayincreased several times. However, directly in themouth of the Volkhov River, the concentration ofbacterioplankton virtually did not change and was(1.60–1.95)⋅106 cells⋅ml–1.

The comparison of summer values of primaryproduction [(68.8–677.8) thousand t C] and organicmatter assimilation by bacterioplankton [(23.9-174.4) ) thousand t C] in the southern coastal regionat the end of 80s shows that even labile organic mat-ter synthesized by phytoplankton was not completelymineralized in this region in spite of considerableintensity of microbiological processes [37,38].Hence, additional discharge of organic matter intothe bay is very undesirable.

The macrozoobenthos of the Volkhov bay differsfrom bottom communities of other parts of the lakecoastal zone in high level of quantitative develop-ment. As early as in 1961 (G.A.Stalmakova’s archive) in the vicinity of the mouth of the Volkhov River,the biomass of macrobenthos amounted to 30 g⋅m–2,whereas average biomass of benthos in the southernpart of the whole coastal zone was 1.7 g⋅m–2 [39].Characterizing the Ladoga Lake by benthos as anoligotrophic lake, the Stalmakova atributed theVolkhov Bay to the eutrophic type according to thestate of bottom fauna. It was observed that benthoswas absent at the location of waste water dischargeof the Syas pulp and paper mill. The archive materi-als of Stalmakova contain lists of mass species ofrelic Gammaridae detected in 1963 in the bay:Monoporeia (Pontoporeia) affinis Lind.,Relictocanthus (Gammaracanthus) lacustris Sarsand Pallasiola (Pallasea) quadrispinosa (Sars). Inlater years, anthropogenic eutrophication and pollu-tion of the bay caused the disappearance from bot-tom biocenoses of the most sensitive species:Relictocanthus and Pallasiola. In 1975–1988,


85

Monoporeia was observed only as single specimensin the northern part of the bay where the influenceof the Volkhov River and the Syas pulp and papermill is less significant.

In shallow parts of the bay (at a depth of 0.25–2.0 m), a new Gammaridae species appeared in re-cent years: a Baikal endemic Gmelinoides fasciatusStebb artificially introduced into the Ilmen Lake andother lakes of the Ladoga basin to improve food ba-sis of fish. Gmelinoides (an euribiont species resist-ant to pollution) completely displaced in shallowparts of the lake Gammarus lacustris Sars which hadpreviously inhabited there [40,41].

On the whole, oligochaetes and chronomids wichare characteristic of the α-mesosaprobic zone domi-nate in the bay. Average biomass of macrozoobenthosin 1992–1998 was to 8.66 ± 2.41 on sands, to 15.66± 2.74 on silty sands, and to 30.6 g⋅m–2 on silts (sin-gle sample). Quantitative parameters of zoobentoscharacterize the bay as an eutrophic water body. Highfraction of chironomids with morphological defor-mations of the mouth parts [42], as well as that ofoligochaetes with deformed setae indicate that thebay is polluted by toxicants [42,43].

The total area of the higher aquatic vegetation inthe Volkhov Bay was 2810 ha according to the dataof 1992–1995. From this area 2600 ha is occupiedby emergent plants communities, and 210 ha bysubmergent vegetation. It is the bay of the LadogaLake wich is most overgrown with emergentmacrophytes. From the end of the 60s (time of thebeginning of intensive anthropogenic eutrophocationof the Ladoga Lake), the area of aquatic vegetationincreased by 25% [44]. The phytomass ofmacrophytes (absolutely dry weight) was 18340 t,more than 1800 t of which accounts for reed andrush. The emergent plants dominate in 19 commu-nities out of 28 macrophyte associations. Over 95%of the total aquatic vegetation area is occupied bycommunities of Phiagmites australis (Cav.) Trin. exStend. and Scirpus lacustris L. The main regions ofthese plants communities are spread in the south-western part of the bay between the Cape Voronovand the Volkhov River mouth. Their width rangesfrom 50 m at the capes till 1000 m between themalso filling the lake-like formations and the channelbetween the Ptinov Island and the mainland.

The belt of reed and rush communities is not con-tinuous but consists of stands of different sizes be-tween which closer to the water boundary groups ofplants with floating leaves or submersed plants arelocated. They are phytocenoses of Nuphar lutea (L.)Smith., Polygonum amphibium L., Potamogeton

natans L., P. gramineus L., Lemna minor L.,Stratiotes aloides L., and Elodea canadensis Michx,which have been developed owing to anthropogeniceutrophication of the lake. On shallow parts of thebay, the small cenoses of Butomus umbellatus L.,Sagittaria sagittifolia L.) and previously non-exist-ent cenoses of Typha angustifolia L. and Lemna.minor are located indicating the result of anthropo-genic impact.

A sandy littoral devoid of higher aquatic vegeta-tion is spread to the east from the Volkhov Rivermouth to the Cape Cherny. Only far from the shorewhere the mobility of the sand sediments disappears,very rare cenoses of Potamogeton perfoliatus L. areobserved. Small areas of silty littoral are occupiedby cenoses of Polygonum amphibium with a mix-ture of some other aquatic plants. All associationsexhibit traces of depression due to anthropogenicfactors.

The spreading of periphyton in the bay is due tothe presence of macrophytes. In the epiphyton(overgrowth on the macrophytes) green filamentousalgae of the genera Mougeotia, Oedogonium,Spirogyra, Zygnema and Cladophora glomeratadominate, among diatoms species of generaAchnanthes, Diatoma, Fragilaria, and Synedra areabundant, and among green algae — Cosmarium andPediastrum. The most intensive development ofepiphyton proceeds on stems and leaves ofPotamogeton perfoliatus. The maximal biomass ofepiphyton for the Ladoga Lake was observed here[45]. The biomass of periphyton from onePotamogeton plant can sometimes exceed the weightof the macrophyte itself more than 1.5 times. In thereed and rush stands growing near the coast,epiphyton developed less intensively: the biomassof communities groups did not exceed 7.1 mg⋅cm–2 ,chlorophyll “a” content did not exceed 43.0 mg⋅cm–

2, and the total primary production did not exceed4.4 g O

2⋅m–2⋅days–1.

The intensive development of green filamentousalgae favours the self-purification of the bay becausethey intensively accumulate heavy metals and otherpollutants from the water, and together withmacrophytes serve as a good “filter” for the watersof the Volkhov River [45].

ConclusionsThe review of the current state of the Volkhov

Bay indicates that it is subjected to a considerableanthropogenic impact. In many parameters, its eco-system essentially differs not only from that of thecentral lake part but also from that of its other bays.


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This bay is an open deltaless estuary part of theLadoga Lake. Owing to active water exchange withthe central lake part, the formation of its water massproceeds to approximately equal extents under theinfluence of river and lake water. Small bay depthfavours rapid and intensive heating of water and itsmixing up to the bottom under the effect of winds.

Its waters have the lowest transparency as com-pared with other lake parts. This is due to the stir-ring up of bottom sediments and the spreading ofriver waters. The near-bottom currents velocitycan attain several tens of centimetres per second;as a result, sediments are subjected to consider-able transport.

Industrial and agricultural enterprises located inthe basins of the Volkhov and Syas rivers, as well aswater transport markedly effect water quality of thebay: In the past decades, the content in water of phos-phorus and nitrogen compounds, heavy metals,phenols, and oil hydrocarbons increases much fasterthan that in the central lake part.

The increase of nutrient load on the bay changedthe quantitative development and species composi-tion of hydrobionts. The results of this studies clearlyshow the eutrophication of the bay, but the evalua-tions of the trophic state of this bay made in the 1980–1990s are ambiguous. Thus, as regards primary pro-duction of phytoplankton, this state corresponds tothe mesotrophic type, for bacteriplankton it wasmesotrophic with some features of the eutrophictype, and for zooplankton it was oligotrophic orweakly mesotrophic. As regards the species compo-sition and quantitative distribution of the zoobenthos,the bay is of the eutrophic type. The increase in thephytomass of higher aquatic plants by 25% also in-dicates that eutrophication of the bay takes place.

The differences in the evaluation of trophic stateare due to different responses of hydrobionts com-munities to changes in chemical composition ofwater and bottom sediments. The effect of toxic sub-stances in the Volkhov Bay is very great, and, there-fore, some species disappeared and the fraction ofbottom invertebrates that was subjected to morpho-logical deformations was very high.

An important feature of functioning of the bayecosystem is its high self-purifying ability deter-mined by many processes. The most important ofthem are active water exchange and destruction oforganic matter in the water. Under present-day con-ditions the destruction in the bay is rather high butdoes not exceed primary production. This fact indi-cates that even labile organic matter undergoes in-complete mineralization.

The final evaluation of the current state of theVolkhov Bay indicates that its ecosystem changedand water quality deteriorated. Therefore, additionalwaste water discharge is dangerous. Incomplete min-eralization of organic compounds of anthropogenicorigin contained in it will lead to inferior oxygenregime of the bay. The increase in pollutants dis-charge will enhance the toxic effect. The rise of nu-trient loading will accelerate eutrofication. All thesenegative factors will favour further deterioration ofwater quality.

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