Ecological Chemistry. St. Petersburg, THESA Russia 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) 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- Syas 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 “Kirishi 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 Neva-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. 75 M.A. Naumenko et al. / Ecological Chemistry 9 (2000) 75–87 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 76 M.A. Naumenko et al. / Ecological Chemistry 9 (2000) 75–87 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.