Ecological Chemistry. St. Petersburg, THESA

Current ecological state of the 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)

Abstract The 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 ecological state of the bay differs considerably from that of other coastal parts of the lake. With respect to economical importance, the catchment area of the Volkhov Bay, is the most developed territory of the Ladoga basin. As a result of increasing nutrient load, eutrophication processes in the bay are obvious. The effect of the waste waters of industrial enterprises favours additional deterioration of water quality 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.

Introduction most serious situation occurred in December 1998 The water quality of the Ladoga Lake undergoes when the dam constructed as long ago as in 1928 for considerable changes caused by anthropogenic ef- sewage collection at the purification works of the fect. This mainly concerns the coastal zones of res- pulp and paper mill broke, and unpurified waste ervoir. The southern part of the catchment area is waters in the amount of 700 thousand m3 were dis- the most economically developed region. It includes charged into the tributary of the Syas River and were the basins of the Volkhov and Syas rivers flowing spread over the adjoining territory. into the Volkhov Bay. Several large enterprises are The systematic discharge of pollutants into the located in the Volkhov River basin, among them the bay and absence of any guarantee for preventing “ nefteorgsintez” and the “Volkhov alu- large-scaled emergency discharges made it indispen- minium” company.*) The latter is one of the main sable to organize the monitoring of the Volkhov Bay sources of phosphorus discharge into the Ladoga and rivers flowing into it. To interpret the monitor- Lake. The waste waters of the Syas pulp and paper ing results and to establish the trends of changes in mill are also discharged into the Volkhov Bay. Ac- the water ecosystem of the bay, a detailed charac- cording to the data of -Ladoga Basin Water terization of its state during many years is neces- Administration, in 1997–1998 about 150 million sary. This information has been accumulated as a m3⋅yr–1 of polluted waste water was discharged into result of systematic studies carried out at the Volkhov the Volkhov and Syas rivers and directly into the Bay by the Limnological Institute of Russian Acad- Volkhov Bay. When emergency situations occur, emy of Sciences and by several other organizations waste waters discharge into the Volkhov Bay and the during four decades. rivers flowing into it can increase many times. The This paper briefly present the most important in- formation about the hydrological, hydrochemical, *) During the existence of this enterprise its name changed sev- eral times. We use below the old name, the “Volkhov aluminium and hydrobiological features of the Volkhov Bay works”, since in this paper data for 30–40 years are reported. — under natural conditions and during constant pollut- Editors’s note. ants discharge into it.

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Morphometry and hydrophysics of the Volkhov Bay The Volkhov Bay is the largest estuary bay of the Ladoga Lake (Fig. 1). The most important feature of the bay is the fact that it is open towards the lake and there are no natural barriers separating it from the main reservoir of the lake. The north boundary of the bay is conventionally taking to be the line be- tween the Cape Voronov on the west and the Volchii Nos promontory in the east [1]. The bay area is 807.8 km2 and the water volume is 6.6 km3 which amounts to about one seventh of both the volume and the coastal zone area of the entire lake limited by the 18-meters isobath [2]. An important feature of the bay’s morphometry is the fact that about 53% of this area belongs to the littoral zone (the boundary of the lake littoral is the 8-meter isobath) which corre- sponds to 25% of the bay volume. The mean bay depth is 8.1 m. The cross-section area at the bound- ary between the Volkhov Bay and the open lake part is 0.486 km2. The Volkhov River, one of the largest tributaries of the Ladoga lake, flows into the Volkhov Bay. Its water catchment area is 80200 km2 and the mean annual water flow rate is 560 m3⋅s–1. The second- large river flowing into the Volkhov Bay, the Syas River, has the water catchment area of 7330 km2 and Fig. 1. Schematic map of the Volkhov Bay of the Ladoga the mean annual water flow rate of 66 m3⋅s–1. The Lake. swampy part of the catchment area of the Volkhov tion. The calculation of the baroclinic Rossby de- River is 8,9% and that of the Syas River is 16%. The formation radius R [5] shows that for the Volkhov residence time of the Vokhov Bay is about 4.5 Bay Coriolis force predominates, especially in win- months. ter time (R = 3–4 km). As regards its morphological features, the The area of river water spreading in the lake de- Volkhov Bay is an open deltaless mouth regions pends not only on discharge volume but also on hy- where wave activity affect the degree of water mix- drodynamic and thermal conditions in the lake. The ing [3]. Its open character favours the penetration of general structure of water dynamics in the Volkhov lake water which mix with the river water in an ap- Bay is distorted by wind activity over its area. In proximately equal ratio (annual average), thus form- winter the northern wind direction dominates and in ing the bay water mass [4]. summer the southern direction prevails. The mean Of particular importance are the spreading of river monthly wind speed in these directions is 6–9 m⋅s–1. waters and the decreasing of its speed in the open The lower wind speed are observed in July and Au- part, which determine the processes of river gust and the maximum speeds in November. At sediments accumulation. On the basis of the ap- strong winds the wind effected phenomena are proach described in ref. [3], it may be concluded clearly distinguished. that the distance at which the flow rate of river wa- The direction of currents in the Volkhov Bay pro- ter becomes equal to the background value is 3–6 foundly effected by wind regime [6]. During south km. Hence, the Volkhov water can spread further that and south-eastern winds, the waters of the Volkhov the eight-meter isobath only due to general lake cir- and Syas rivers are directed towards the Petrokrepost culation. The cyclonic circulation existing in the bay, and their effect is recorded at the source of the Ladoga Lake in spring and summer penetrates freely Neva [7]. However, the degree of river water dilu- into the bay and involves the water of the rivers into tion has not been studied in detail. its motion. Therefore, the river water after flowing The prevailing types of bottom sediments in the into the bay deviates to the east in its further mo- bay are sands of various sizes and boulders, although

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Fig. 2. Average annual (multiyear) distribution of water surface temperature (°C) referred to the middle of the month. silty sands and even silts are also encountered. In here and 12 thousand m3 along the eastern shore. stormy weather, the bottom depths from which the However, this transport has no great effect on the erosion of bottom sediments begins (wave basis) can morphology of the western shore. Simultaneously reach 11–18 m [8]. Wave current velocity at a depth the eastern shore is continuously eroded and the bot- of 5 m can exceed 0.8 m⋅s–1 [9]. Hence, bottom tom slope gradually decreases which is accompa- sediments are influenced by waves over virtually the nied by the retreat of the shore line. entire area of the Volkhov Bay. At the north eastern boundary of the bay in the The study of sediments transport along the shores region of the Volchii Nos and Storozhensky capes, made it possible the establish the zones of erosion, the divergence of wave energy fluxes occurs. transport, and accumulation of material [10]. Its flow Sediments in the amount of 800 thousand m3 are along the western shore of the Volkhov Bay is di- transported from the erozion zone to the south into rected from the south to the north. The focus of its the Volkhov Bay. The eastern shore and the bottom accumulation is located between the mouths of the slope in its water boundary area is being continu- Volkhov and Syas rivers. Along the western bay ously eroded, whereas at the lower slow parts (lower shore, 22 thousand m3 of sediments are transported than five meter isobath) deposits are accumulated.

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Fig. 3. Average long-term distribution of water temperature of the Volkhov Bay and air temperature over the water surface: 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.

Observations carried out for establishing the correct coastal lake water [12], river water is spread above location of waste water discharge of the Syas pulp lake water. and paper mill [11] have shown that solid residues In June, the bay exhibits the greatest spatial ther- from wood treatment were accumulated mainly to mal inhomogeneity. From July the degree of water the east of discharge site. homogeneity increases, and in August – September The Volkhov Bay is one of the warmest bays of water temperature becomes the same virtually the Ladoga Lake. Ice destruction starts in April at throughout the bay. the mouth of the Volkhov River and from the side of In summer time, the main role in the formation open lake with simultaneous increase in water flow of the thermal structure of the Volkhov Bay is played in the river. Fig.2 shows the mean temperature dis- by heat arrival at water surface as well as by wind tribution in the bay for many years. In the middle of regime. Since the bay is shallow and open, wind May, the spring thermal frontal zone (thermobar) is mixing reaches the bottom at mean wind speed, located at its north boundary and prevents the spread- which leads to destruction of temperature stratifica- ing the river water to the lake centre. Since at this tion and to rapid heating or cooling of the water mass time the water of rivers is heated more rapidly than (Fig. 3-A). The diurnal course of water temperature 78 M.A. Naumenko et al. / Ecological Chemistry 9 (2000) 75–87

Fig. 4. Average monthly transparency (white disk depth), 1958–1998: 1 — average values, 2 — mean-square deviation, 3 — standard error. reaches the bottom. However, on calm days a con- lower than in other regions of the coastal lake part. siderable vertical temperature gradient appears which Images made from space show distinctly more prevents heat exchange between surface and bottom turbid Volkhov-waters (Fig. 5). They can be followed layers. The change in water temperature dispersion at the wind effected phenomena in the period of open with time (Fig. 3-B) shows that a considerable tem- water (April, May, and June) along the eastern shore perature gradient can exist in bottom waters layers of the bay upper to its boundary. in July and August as was reported by J.V. Molchanov a long time ago [13]. This is due to Hydrochemistry of the Volkhov Bay the exchange between cold water of the central lake Hydrochemical studies in the Volkhov Bay were part and more heated coastal water. carried out from the 1930s to the end of the 1990s Maximum air temperature over the Volkhov Bay [15–21]. The problem of water quality was consid- exists at the end of July (Fig. 3-C), and the maxi- ered as far back as in 1931 in connection with infe- mum water surface temperature is observed with a rior spawning conditions [11]. certain delay: in the first decade of August. The hydrochemical regime of the bay is formed The Volkhov Bay is characterized by the lowest under the influence of several factors. The principal water transparency as compared with other parts of role is played by river waters. Seasonal water tem- the coastal zone of the lake. This is caused by the perature distribution and wind activity also produce flowing in of river waters and the stirring up of bot- a considerable effect. tom waters. Suspended particles concentration in the The Volkhov and the Syas rivers are character- Volkhov River in spring can attain 18 g⋅m–1, which ized by higher major ions content in water (as com- is 2–3 times as much as in the lake centre. Moreo- pared with the main tributaries of the lake). The mean ver, 30–50% of particles consist of organic matter annual value of major ions content in water of the [14]. Maximum turbidity (and minimum transpar- Syas River is 120 mg⋅l–1, and the maximum value ency) of water in the bay is observed in May (Fig. during winter low water level can attain 300 mg⋅l–1. 4). In this period, water transparency in the bay is The same mean annual values for the Volkhov River 60% lower than throughout the other coastal part of are about 150–160 mg⋅l–1. In low water years the the lake. After the end of spring, high water and up range of major ions content is 90–320 mg⋅l–1 and in to October, statistically significant differences be- high water years it is 70–220 mg⋅l–1. tween mean monthly water transparency values in The chemical composition of the water of the the bay disappear, although transparency remains Volkhov River differs from that of all other rivers of

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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. the Ladoga basin. Although this water with respect From the beginning of 1970s the Volkhov alu- to the ratio of major ion belongs to hydrocarbon- minium works became the main source of this ele- calcium type, in their anion composition during low ment because they began to use nephelines as raw water level period, chloride ions predominate over material for production of aluminium. The greatest sulphate ions, whereas in spring and during rainy amount of phosphorus was discharged into the bay high water, the contributions of chlorides and sul- from the catchment area at the end of 70s and at the phate are equal. beginning of the 80s (Table 1) [22,25]. In these years The major ions content of the Volkhov bay water during the ice-free period, the maximum total phos- varies over a wide range: from 170 mg⋅l–1 to values phorus content in the bay water attained 260 µg⋅l–1 close to the lake values (65 mg⋅l–1). Among the main at a mean value of 70 µg⋅l–1. In the winter of 1977– tributaries the lake, the Volkhov River is distin- 1978 in the zone close to the mouth of the Volkhov guished by high (as compared to the and the River, concentrations of 360–380 µg⋅l–1 were ob- Vuoksa rivers) phosphorus content and is the main served [18]. source of this element in the lake. These features of Partial transition of the Volkhov aluminium works the river result from the combined effect of phisico- to the system of circulating water supply and the geographical and anthropogenic factors [22,23]. decrease of production at the works and at the Syas

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Table 1 Mean annual concentrations of phosphorus and nitrogen in river water and waste water and discharge of nutrients in the Volkhov Bay Total phosphorus Total nitrogen Source of discharge Concentration, Discharge, Concentration, Discharge, Years –1 –1 Years –1 –1 µg⋅l t⋅yr mg⋅l t⋅yr 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 pulp and paper mill favoured a decrease in phospho- Local variations are determined by spreading of river rus discharge into the Volkhov Bay. In the 90s the and lake water through the bay. The labile compo- average content and the range of total phosphorus nents of organic matter are indirectly indicated by ⋅ –1 concentration in the bay water decreased almost BOD5 values which seldom exceed 6 mg O2 l . twice (Table 2), although local differences remained Content of oxygen dissolved in water is mainly considerable. Maximum phosphorus concentrations determined by thermal conditions. However, produc- are charactreristic of coastal parts and the zone ad- tion and destruction processes also play an impor- joining the mouth of the Volkhov River. The mini- tant role. Relative oxygen content ranges from 65 to mum values do not exceed concentrations typical of 125% saturation (Table 2). Water supersaturated with the open lake (15–20 µg⋅l–1). Inorganic phosphorus oxygen is accompanied by high pH values, which fraction is on the average 13–36% of its total con- indicates that the oxygen maximum is of the photo- tent. Its concentration at some parts during inten- synthetic origin. Minimum oxygen content was ob- sive photosynthesis of phytoplankton can reduce to served in the vicinity of the mouth of the Volkhov values below detection limit, although near the mouth River and in shallow water near the coast. of the Volkhov River even in summer concentration The water of the bay is characterized by higher increase to 80–100 µg⋅l–1 is observed. concentrations of heavy metals than that in the open Nitrogen discharge into the bay did not change lake (Table 3) [22]. The reason for relatively high greatly by the end of the 90s as compared to 1967– content of iron, aluminium, and manganese is that 1988. A certain tendency to decreasing total nitro- the catchment areas of rivers flowing into the bay gen content in the bay water appeared. Concentra- are rather swampy. The spatial distribution of metal tion range has always been smaller than for phos- compounds over the reservoir is very inhomogene- phorus, and the mean value was close to those char- ous. Near the mouth of the Volkhov River, iron, alu- acteristic of lake water. Nitrates were always present minium, and manganese concentration exceed more in the bay water, their average concentration in the than 1.5–3 times those in the other parts of the bay. summers of 1994 and 1995 was close to 100 µg⋅l–1, Manganese is characterized by the greatest concen- and in the autumn of 1995 it was 190 µg⋅l–1. tration variation. In contrast, lead concentrations Organic matter discharge from the catchment area throughout the bay change only slightly. Changes in into the Volkhov Bay (just as that into the whole lake) copper content are mainly caused by the intensity of depends mainly on water level of the year and remains phytoplankton development because it accumulates relatively stable for the long-term series [25,26]. Wa- copper. High copper concentrations are observed in ter colour in the bay ranges from 140 to 25 Pt-units. In regions far from the mouth of the Volkhov River. other words, it can exceed three or four times water Seasonal distribution of metal compounds is usu- colour in central lake part, which is due to the domina- ally characterized by high spring concentrations as tion of allochtonous organic matter. compared with summer and autumn values. Seasonal variations in organic carbon concentra- Oil hydrocarbons and phenols content in the wa- tions are slight but exceed those for the open lake. ter of the bay is most often within the LAC limits

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Table 2 Hydrochemical characteristics of the the Volkhov Bay Spring (V–VI) Summer (VII–VIII) Autumn (IX–X) Units Component Years Mean Range Mean Range Mean Range value value value ⋅ –1 O2 mg l 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 µ ⋅ –1 Ptot g l 1988–1998 31 18–88 34 14–120 39 15–140 µ ⋅ –1 Pmin g l 1988–1998 4 < 1–12 12 < 1–100 12 2–54 µ ⋅ –1 Ntot g l 1988–1998 590 520–680 630 500–820 810 760–900 ⋅ –1 Corg mg l 1988–1998 13.2 5.5–20.4 10.9 6.5–20.4 9.3 6.1–17.6 BOD ⋅ –1 1988–1998 1.9 1.1–2.7 1.5 0.6–2.6 1.0 6.1–17.6 5 mg O2 l Oil µg⋅l–1 1992–1998 ––44 6–89 56 11–100 hydrocarbons 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.

(50 and 1 µg⋅l–1, respectively). However, in the re- plete mixing of river and lakes waters in this period gion close to the Volkhov mouth, high values of their takes place more rapidly [18]. For many years in concentrations are sometimes observed, which may June and especially in July, the region of high be caused by waste water discharge into the river. hydrocarbonates content indicating the spreading of Oil hydrocarbons and phenols concentrations in- the river Volkhov water in the lake can be following crease in autumn over those in summer (data of V.A. up to the latitude of the Valaam Island [17,19,20]. Shcherbak and N.L. Krylenkova). This may be due to more intensive destruction processes in summer. Hydrobiological characterization of the In winter and periodically in summer in calm Volkhov Bay weather, water stratification can be distinctly ob- Hydrological and hydrochemical features of the served in the bay. It is especially well distinguished Volkhov Bay determine specific properties of its from water colour and phosphorus content (Table biocenosis. Phytoplankton of the bay differs from 4). In winter, denser river water is revealed in near- that in other parts of the lake both in the species com- bottom horizons at a distance of 30–35 km from the position and the structure of the biomass and func- Volkhov mouth. In contrast, in summer the water of tional parameters. These differences are retained in this river is spread along the surface, although com- all seasons. In spring and autumn, the phytoplankton is dominated by the Bacillariaphyta. Chlorophyll “a” and the total biomass in the bay isolated by the Table 3 thermobar are ten times higher than in the central Concentration of heavy metal compounds part of the lake [27,28]. In summer, these differences in the Volkhov Bay water, µg⋅l–1 (1988–1998) are not so sharp. Nevertheless, the phytoplankton of the bay is always richer than that in the main pelagial Bay parts area. Near the mouth Far from the mouth The current state of this community is consid- of the Volkhov River of the Volkhov River Elements ered on the basis of data of 1992–1997 (August). Limits of Limits of Mean concentration Mean concentration The phytoplankton is dominated by the Cyanophyta value changes value changes (50% of the total biomass), Cryptophyta (20%), Fe 278 80–469 172 54–362 Bacillariophyta (13%), and Chlorophyta (7%). In Al 109 36–2525217–246 the coastal parts of the bay, species of the Microcystis Mn 42 3.5–94.5 13.3 2.5–26.7 genus: M. aeruginosa Kutz. emend Elenk., M. Cu 6.8 0.4–20.4 10.7 0.9–50.4 reinboldii (Wood) Forti, M. viridis (A. Braun.) Lemm., and M. wezenbergii (Kamarek) Star. are Pb 1.5 0.3–5.4 1.3 0.2–5.7 numerous. Most of them are toxic. The biomass of 82 M.A. Naumenko et al. / Ecological Chemistry 9 (2000) 75–87

Table 4 Vertical distribution of water colour and phosphorus content in the Volkhov Bay water Distance from Phosphorus, No. of the mouth of the µ ⋅ –1 collection site Horizon, m g l Water colour, Volkhov River, (see Fig. 1) P P Pt-units km tot min 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) 15.50.5442339 6.9 300 240 99 25 ∼ 30 0401839 10 24 21 39 15 94 51 – 20 266 222 120 blue-green algae attained 2–3 g⋅m–3 in some years. mainly caused by meteorological conditions in ob- These values indicate water “bloom” and deteriora- servation years. These results indicate that the state tion of water quality. In the main part of the bay, of phytoplankton is stable under present conditions. species of the Anabaena genus dominated: : A. According to summer data, the mean values circinalis Raben., A. flos-aquae Breb., A. spiroides ( X± SE) for the biomass were 2.1 ± 0.24 g⋅m–3, for Kleb. and Aphanizomenon flos-aquae (L.) Ralfs. The chlorophyll “a” 8.3 ± 0.7 mg⋅m–3, and for photosyn- main species of Cryptophyta were Cryptomonas thesis intensity 312 ± 26 mg C⋅m–3⋅day–1. According erosa Ehr. and Rhodomonas lacustris Pasch. et Rutt. to existing classifications of the trophic state for Among diatoms, the most frequent species were phytoplankton, the bay belongs to true mesotrophic Stephanodiscus binderanus (Kutz.) Krieg., St. type. hantzschii Grun. and Aulacoseira italica (Ehr.) Sim. Zooplankton is one of the most important com- This situation is due to unstable summer stratifica- munities of the ecosystem ensuring the mineraliza- tion in the bay, which is often perturbed by wind tion of the autochthonous and allochtonous organic mixing favouring the maintenance of heavy cells matter. Its role in phosphorus regeneration and its diatoms in water. The presence of numerous species involvement in biotic circulation is considerable. of green algae (Scenedesmus Meyen and Pediastrum Moreover, it is the main component of the food ba- Meyen) indicate sufficiently high concentrations of sis for planktophagous fish and for all young fish. nutrients. The community structure of phytoplankton The Volkhov Bay is traditionally considered as shows relatively high trophic state of the bay. one of the most productive (for plankton) regions of Phytoplankton distribution throughout the bay is the Ladoga Lake [29]. The most usual mass forms very inhomogeneous. Biomass ranges from 0.5 to of zooplankton are Asplanchna priodonta (Gosse), 6.6 g⋅m–3, chlorophyll “a” content from 4.3 to 15.8 Keratella cochlearis (Gosse), Conochilus unicornis mg⋅m–3, and photosynthesis intensity from 120 to (Rousselet), species of genera Polyarthra and 471 mg C⋅m–3⋅day–1. Horizontal heterogeneity of Synchaeta — from Rotatoria; Thermocyclops phytoplankton is due to specific features of hydro- oithonoides (Sars), Mesocyclops leuckarti (Claus), dynamic regime of the bay. However, seasonal vari- Eudiaptomus gracilis (Sars), Eurytemora lacustris ations of mean values are not great: the biomass (Poppe), Daphnia cristata (Sars), Bosmina ranged from 1.5 to 2.4 g⋅m–3, chlorophyll “a” con- crassicornis (P.E. Muller), Limnosida frontosa (Sars) tent from 7.5 to 92 mg⋅m–3, and photosynthesis in- — from Crustacea. tensity from 240 to 356 mg C⋅m–3⋅day–1, which is All data refer to the period of mass zooplankton within the normal value for this community that is development (July – August) in 1990–1998. The

83 M.A. Naumenko et al. / Ecological Chemistry 9 (2000) 75–87 numbers, of net zooplankton for some years ranged partially spreading in the bay was directed along the from 16.4 to 57.4 thousand ind.⋅m–3 and were on the north-eastern coast, and, very high bacterial abun- average 30.4 (11.7) thousand ind.⋅m–3 (in parenthe- dance was detected at a distance of about 6 km and ses here and below — mean square deviation). The then decreased to background values (0.35–0.40)⋅106 numbers of Copepoda somewhat exceeded that of cells⋅ml–1 [35]. Cladocera: 52 and 44%, respectively. The biomass In 1994–1998, maximum (for the lake as a whole) values of net zooplankton varied over a wider range microbiological parameters was observed in the bay. for several years: 0.35–2.35 g⋅m–3 and were on the They corresponded to the mesotrophic level with average 0.90 (0.56) g⋅m–3. However, if two extreme some features of the eutrophic state. Thus, mean values were excluded the range became much more summer values of bacterial density and heterotrophic ⋅ –3 ⋅ 6 narrow : 0.45–1.04 g m . The share of Cladocera in assimilation of CO2 in the bay were 2.05 10 the biomass greatly exceeded that of Copepoda.: 56 cells⋅ml–1 and 7.7 µg C⋅l–1⋅day–1, respectively. The and 29%, respectively. This should be considered a maximum values attained 10.0⋅106 cells⋅ml–1 and characteristic feature of the Volkhov Bay as com- 28.2 µg C⋅l–1⋅day–1, respectively. In connection with pared to other lake parts. Accordingly, in some years, the euthrophication of the Ladoga Lake, the abso- the Cladocera (L. frontosa, D. cristata, B. lute values of microbiologiacal parameters in the bay crassicornis), as well as large Rotatoria (A. increased several times. However, directly in the priodonta) dominated in the biomass. mouth of the Volkhov River, the concentration of Considering the bay zooplankton one should bacterioplankton virtually did not change and was mention that larvae of Dreissena polymorpha (Pallas) (1.60–1.95)⋅106 cells⋅ml–1. were detected in it (in 1995 and 1998 ) the mass The comparison of summer values of primary spreading of which can lead to important negative production [(68.8–677.8) thousand t C] and organic consequences. matter assimilation by bacterioplankton [(23.9- The evaluation of long-term changes in the bay 174.4) ) thousand t C] in the southern coastal region zooplankton is difficult and tentative because the data at the end of 80s shows that even labile organic mat- are scarce. However, taking into account the data of ter synthesized by phytoplankton was not completely the end of the 1940s [29] one can speak about the mineralized in this region in spite of considerable certain stability of net zooplankton development. intensity of microbiological processes [37,38]. Unfortunately, the data on its small-size fractions Hence, additional discharge of organic matter into for 1947–1949 are absent, and, therefore, it is risky the bay is very undesirable. to draw conclusions about a great increase in num- The macrozoobenthos of the Volkhov bay differs bers and changes in structure of zooplankton because from bottom communities of other parts of the lake of eutrophycation [30–32]. The general level of coastal zone in high level of quantitative develop- zooplankton development in the bay (according to ment. As early as in 1961 (G.A.Stalmakova’s archive formal criteria [33,34]) can be considered to be char- ) in the vicinity of the mouth of the Volkhov River, acteristic of oligotrophic or weakly mesotrophic res- the biomass of macrobenthos amounted to 30 g⋅m–2, ervoirs. In some years, at mass Cladocera develop- whereas average biomass of benthos in the southern ment, biomass values can correspond to a higher part of the whole coastal zone was 1.7 g⋅m–2 [39]. trophic state. Characterizing the Ladoga Lake by benthos as an At the beginning of the 60s, on the background oligotrophic lake, the Stalmakova atributed the of the general low bacterioplankton concentration Volkhov Bay to the eutrophic type according to the [(0.18–0.30)⋅106 cells⋅ml–1), the Volkhov bay into state of bottom fauna. It was observed that benthos which large quantities of suspended particles and was absent at the location of waste water discharge nutrients are discharged, was distinguished by rela- of the Syas pulp and paper mill. The archive materi- tively considerable micro-organisms densities (about als of Stalmakova contain lists of mass species of 0.5⋅106 cells⋅ml–1). Directly at the mouths of the relic Gammaridae detected in 1963 in the bay: Volkhov and the Syas rivers, even higher bacterial Monoporeia (Pontoporeia) affinis Lind., numbers (1.75⋅106 and 4.2⋅106 cells⋅ml–1, respec- Relictocanthus (Gammaracanthus) lacustris Sars tively) were observed. In the region of the collector and Pallasiola (Pallasea) quadrispinosa (Sars). In of the Syas pulp and paper mill, the total bacterial later years, anthropogenic eutrophication and pollu- numbers and concentration of saprophytic bacteria tion of the bay caused the disappearance from bot- attained tremendous values: 17.6⋅106 and 2.8⋅10 3 tom biocenoses of the most sensitive species: cells⋅ml–1, respectively [35,36]. The collector stream Relictocanthus and Pallasiola. In 1975–1988,

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Monoporeia was observed only as single specimens natans L., P. gramineus L., Lemna minor L., in the northern part of the bay where the influence Stratiotes aloides L., and Elodea canadensis Michx, of the Volkhov River and the Syas pulp and paper which have been developed owing to anthropogenic mill is less significant. eutrophication of the lake. On shallow parts of the In shallow parts of the bay (at a depth of 0.25– bay, the small cenoses of Butomus umbellatus L., 2.0 m), a new Gammaridae species appeared in re- Sagittaria sagittifolia L.) and previously non-exist- cent years: a Baikal endemic Gmelinoides fasciatus ent cenoses of Typha angustifolia L. and Lemna. Stebb artificially introduced into the Ilmen Lake and minor are located indicating the result of anthropo- other lakes of the Ladoga basin to improve food ba- genic impact. sis of fish. Gmelinoides (an euribiont species resist- A sandy littoral devoid of higher aquatic vegeta- ant to pollution) completely displaced in shallow tion is spread to the east from the Volkhov River parts of the lake Gammarus lacustris Sars which had mouth to the Cape Cherny. Only far from the shore previously inhabited there [40,41]. where the mobility of the sand sediments disappears, On the whole, oligochaetes and chronomids wich very rare cenoses of Potamogeton perfoliatus L. are are characteristic of the α-mesosaprobic zone domi- observed. Small areas of silty littoral are occupied nate in the bay. Average biomass of macrozoobenthos by cenoses of Polygonum amphibium with a mix- in 1992–1998 was to 8.66 ± 2.41 on sands, to 15.66 ture of some other aquatic plants. All associations ± 2.74 on silty sands, and to 30.6 g⋅m–2 on silts (sin- exhibit traces of depression due to anthropogenic gle sample). Quantitative parameters of zoobentos factors. characterize the bay as an eutrophic water body. High The spreading of periphyton in the bay is due to fraction of chironomids with morphological defor- the presence of macrophytes. In the epiphyton mations of the mouth parts [42], as well as that of (overgrowth on the macrophytes) green filamentous oligochaetes with deformed setae indicate that the algae of the genera Mougeotia, Oedogonium, bay is polluted by toxicants [42,43]. Spirogyra, Zygnema and Cladophora glomerata The total area of the higher aquatic vegetation in dominate, among diatoms species of genera the Volkhov Bay was 2810 ha according to the data Achnanthes, Diatoma, Fragilaria, and Synedra are of 1992–1995. From this area 2600 ha is occupied abundant, and among green algae — Cosmarium and by emergent plants communities, and 210 ha by Pediastrum. The most intensive development of submergent vegetation. It is the bay of the Ladoga epiphyton proceeds on stems and leaves of Lake wich is most overgrown with emergent Potamogeton perfoliatus. The maximal biomass of macrophytes. From the end of the 60s (time of the epiphyton for the Ladoga Lake was observed here beginning of intensive anthropogenic eutrophocation [45]. The biomass of periphyton from one of the Ladoga Lake), the area of aquatic vegetation Potamogeton plant can sometimes exceed the weight increased by 25% [44]. The phytomass of of the macrophyte itself more than 1.5 times. In the macrophytes (absolutely dry weight) was 18340 t, reed and rush stands growing near the coast, more than 1800 t of which accounts for reed and epiphyton developed less intensively: the biomass rush. The emergent plants dominate in 19 commu- of communities groups did not exceed 7.1 mg⋅cm–2 , nities out of 28 macrophyte associations. Over 95% chlorophyll “a” content did not exceed 43.0 mg⋅cm– of the total aquatic vegetation area is occupied by 2, and the total primary production did not exceed ⋅ –2⋅ –1 communities of Phiagmites australis (Cav.) Trin. ex 4.4 g O2 m days . Stend. and Scirpus lacustris L. The main regions of The intensive development of green filamentous these plants communities are spread in the south- algae favours the self-purification of the bay because western part of the bay between the Cape Voronov they intensively accumulate heavy metals and other and the Volkhov River mouth. Their width ranges pollutants from the water, and together with from 50 m at the capes till 1000 m between them macrophytes serve as a good “filter” for the waters also filling the lake-like formations and the channel of the Volkhov River [45]. between the Ptinov Island and the mainland. The belt of reed and rush communities is not con- Conclusions tinuous but consists of stands of different sizes be- The review of the current state of the Volkhov tween which closer to the water boundary groups of Bay indicates that it is subjected to a considerable plants with floating leaves or submersed plants are anthropogenic impact. In many parameters, its eco- located. They are phytocenoses of Nuphar lutea (L.) system essentially differs not only from that of the Smith., Polygonum amphibium L., Potamogeton central lake part but also from that of its other bays.

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This bay is an open deltaless estuary part of the The final evaluation of the current state of the Ladoga Lake. Owing to active water exchange with Volkhov Bay indicates that its ecosystem changed the central lake part, the formation of its water mass and water quality deteriorated. Therefore, additional proceeds to approximately equal extents under the waste water discharge is dangerous. Incomplete min- influence of river and lake water. Small bay depth eralization of organic compounds of anthropogenic favours rapid and intensive heating of water and its origin contained in it will lead to inferior oxygen mixing up to the bottom under the effect of winds. regime of the bay. The increase in pollutants dis- Its waters have the lowest transparency as com- charge will enhance the toxic effect. The rise of nu- pared with other lake parts. This is due to the stir- trient loading will accelerate eutrofication. All these ring up of bottom sediments and the spreading of negative factors will favour further deterioration of river waters. The near-bottom currents velocity water quality. can attain several tens of centimetres per second; as a result, sediments are subjected to consider- References able transport. 1. Sailing Directions of the Ladoga Lake (1986) Ed. GUNiO Industrial and agricultural enterprises located in MO, , 163 p. (in Russian). the basins of the Volkhov and Syas rivers, as well as 2. Naumenko (1995) New definition of morphometric char- acteristics of the Ladoga Lake. Dokl. Ross. Akad. Nauk. water transport markedly effect water quality of the 345, 514–517 (in Russian). bay: In the past decades, the content in water of phos- 3. Mikhailov V.N., Rogov M.M., and Chistyakov A.A. phorus and nitrogen compounds, heavy metals, (1986) River Deltas. Gidrometeoizdat, Leningrad, 280 phenols, and oil hydrocarbons increases much faster p. (in Russian). than that in the central lake part. 4. Gusakov B.L. and Petrova N.A. (1992) Effect of water and anthropogenic loads on single parts of the lake coastal zone. The increase of nutrient load on the bay changed In: The Ladoga Lake — Criteria of the Ecosystem State. the quantitative development and species composi- Eds. N.A. Petrova and A.Yu. Terzhevik. Nauka, St. tion of hydrobionts. The results of this studies clearly Petersburg, pp. 266–279 (in Russian). show the eutrophication of the bay, but the evalua- 5. Masse A. and Murthy C. (1992) Analysis of the Niagara tions of the trophic state of this bay made in the 1980– River plume dynamics. J. Geophys. Resh. 97, 2403–2407. 1990s are ambiguous. Thus, as regards primary pro- 6. Okhlopkova A.N. (1961) Study of the Ladoga lake curents using a dynamic method. Okeanologiya. 1, 1025–1033 (in duction of phytoplankton, this state corresponds to Russian). the mesotrophic type, for bacteriplankton it was 7. Kruchkov A.M. (1997) Long-term trends of conductivity mesotrophic with some features of the eutrophic in Neva River water by its outflow from . Proc. type, and for zooplankton it was oligotrophic or of the Second Int. Lake Ladoga Symp. Publ. of Karelian weakly mesotrophic. As regards the species compo- Institute. No. 117. Joensuu, pp. 164–168. 8. Role of Wave Processes in Development of Benthos Com- sition and quantitative distribution of the zoobenthos, munity of Large Lakes (1990) Ed. I.M. Raspopov. Nauka, the bay is of the eutrophic type. The increase in the Leningrad, 112 p. (in Russian). phytomass of higher aquatic plants by 25% also in- 9. Vorontsov F.F. (1966) Wave processes on the Ladoga Lake. dicates that eutrophication of the bay takes place. In: Hydrological Regime and Water Blance of the Ladoga The differences in the evaluation of trophic state Lake. Ed. Len. St. Univers., Leningrad, pp. 247–264 (in Russian). are due to different responses of hydrobionts com- 10. Barkov L.K., Shcherbakov E.M., and Usenkov S.M. (1983) munities to changes in chemical composition of Composition and dynamics of recent bottom sediments in water and bottom sediments. The effect of toxic sub- the southern part of the Ladoga Lake. Vestnic LGU (the stances in the Volkhov Bay is very great, and, there- Leningrad State University). No 6, pp. 32–40 (in Russian). fore, some species disappeared and the fraction of 11. Pravdin I.F. (1931) Review of fishery in the Volkhov bay bottom invertebrates that was subjected to morpho- of the Ladoga Lake and in the Syas River. Izvestiya Len. Nauchno-Issledov. Ikhtiologicheskogo Inst. XII, issue 2, logical deformations was very high. 1–77 (in Russian). An important feature of functioning of the bay 12. Veselova M.F. (1968) Role of river waters in thermal bal- ecosystem is its high self-purifying ability deter- ance of the Ladoga Lake. In: Thermal Regime of the Ladoga mined by many processes. The most important of Lake. Eds. S.V. Kalesnik and N.P. Smirnova. LGU, Lenin- them are active water exchange and destruction of grad, pp. 218–222 (in Russian). organic matter in the water. Under present-day con- 13. Molchanov I.I. (1945) The Ladoga Lake. Leningrad – Moscow, 557 p. (in Russian). ditions the destruction in the bay is rather high but 14. Yegorov Yu.S., Rumyantsev V.B., and Yudin E.A. (1982) does not exceed primary production. This fact indi- Optical parameters and suspended particles in lake water. cates that even labile organic matter undergoes in- In: Anthropogenic Eutrophication of the Ladoga Lake. Ed. complete mineralization. N.A. Petrova. Nauka, Leningrad, pp. 61–69 (in Russian).

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15. Mosevich N.A. (1931) Hydrological and hydrochemical years. In: Sbornik nauch. Trudov GosNIORKH. Issue studies in the Volkhov bay of the Ladoga Lake in March 314, pp. 192–230 (in Russian). 1930 Izvestiya Leningr. nauch.-issled. ikhtiolog. inst. 12, 31. Ogorodnikova V.A. (1995) Zooplankton in southern Lake issue 1, 236–246 (in Russian). Ladoga: structure and abundance changes reflecting an- 16. Alferovskaya M.M. and Protasova V.I. (1956) Obser- thropogenic input. Abstr. of the First Internat. Lake Ladoga vations of temperature, gaseous, and salt properties of Symp., 1993, Joensuu. No. 112. Joensuu, pp. 29–34. the Ladoga Lake water. Izvestiya VNIORKH. 38, 1–42 32. Lavrentyeva.G.M., Ogorodnikova V.A., Susloparova O.N. (in Russian). and Tereshenkova T.V. (1997) Changes in the structure of 17. Raspletina G.F., Ulianova D.C., and Sherman E.E. (1967) plankton communities in southern Lake Ladoga under con- Hydrochemistry of the Ladoga Lake. In: Hydrochemistry ditions of technogenic pressure. Proc. of the Second and Hydrooptics of the Ladoga Lake. Nauka, Leningrad, Internat. Lake Ladoga Symp., 1996. Joensuu, 94–102. pp. 60–122 (in Russian). 33. Kitaev S.P. (1984) Ecological bases of bioproductivity of lakes 18. Raspletina G.F. (1982) Regime of nutrients. In: In: Anthro- in different natural zones. Moscow, 207 p. (in Russian). pogenic Eutrophication of the Ladoga Lake. Ed. N.A. 34. Andronikova I.N. (1996) Structural-functional organiza- Petrova. Nauka, Leningrad, pp. 79–100 (in Russian). tion of zooplankton of lake ecosystems of different trophic 19. Currant state of the ecosystem of the Ladoga Lake (1987) types. Nauka, St. Petersburg, 189 p. (in Russian). Eds. N.A. Petrova and G.F. Raspletina. Nauka, Leningrad, 35. Mosevich M.V. (1962) Effect of waste water of the Syas 213 p. (in Russian). and pulp-and-paper mills on the microflora of 20. Raspletina G.F. and Gusakov B.L. (1988) Regime of nu- the Ladoga Lake. Nauch.-tech. Bulleten GosNIORKH. 16, trients of the Ladoga Lake in conditions of anthropogenic pp. 46–51 (in Russian). eutrophication. Trudy Gos. Gidrologich. Inst. Issue 321, 36. Rodina A.G. and Kuzmitskaya N.K. (1968) Quantity and 66–73 (in Russian). distribution of microorganisms in the Volkhov Bay of the 21. Ladoga Lake — criteria of the ecosystem state (1992) Eds. Ladoga Lake. Gidrobiologich. Zhurnal. 4, No 1, 42–50 (in N.A. Petrova and A.Yu. Terzhevik. Nauka, St. Petersburg, Russian). 326 p. (in Russian). 37. Kapustina L.L. (1992) Time-dimensional distribution and 22. Raspletina G.F. (1982) Change in hydrochemical regime of functional characteristics of bacterioplankton. In: Ladoga tributaries as a result of human activity on thecatchment area. Lake — criteria of the ecosystem state (1992) Eds. N.A. In: Anthropogenic Eutrophication of the Ladoga Lake. Ed. Petrova and A.Yu. Terzhevik. Nauka, St. Petersburg, pp. N.A. Petrova. Nauka, Leningrad, pp. 42–50 (in Russian). 146–179 (in Russian). 23. 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(1994) Spatial dis- of Volkhov Bay of the Ladoga Lake and the Volkhov and tribution of phytoplankton in Lake Ladoga during summer Syas rivers. Abstr. to Conf.: Biol. Resources of the White – autumn 1992–1993. University of Joensuu Publication Sea and the Inner Rreservoirs of the European North. Pp. of Karelian Institute, No. 111. Joensuu, pp. 64–69. 124–125 (in Russian). 28. Letanskaya G.I. and Protopopova E.V. (1997) 43. Slepukhina T.D. (1994) Long-term changes in Oligochaeta Phytoplankton of Lake Ladoga during the spring thermal communities of Lake Ladoga. Abstr. of 6th Int. Symp. on front period. Proc. of the Second Int. Lake Ladoga Symp. Aquatic Oligochaetes. Strömstad. . Sept. 5–10, Publ. of Karelian Institute. No. 117. Joensuu, pp. 213–219. 1994. Strömstad, Sweden, p. 25. 29. Sokolova M.F. (1956) Zooplankton of the Ladoga Lake. 44. Coastal-aquatic ecotons of large lakes (1998) Ed. I.M. Izvestiya VNIORKH. 38, 53–65 (in Russian). Raspopov. St. Petersburg, 54 p. (in Russian). 30. 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