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Daphnia-pH#3 - Estonian Journal of Ecology 2008 57 3 214228...

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Estonian Journal of Ecology, 2008, 57 , 3, 214°228 doi: 10.3176/eco.2008.3.04 214 The pelagic food web in forest lakes affected by alkaline mining waste in NW Russia Ismo J. Holopainen a ! , Anna-Liisa Holopainen a , Eeva Huitu b , Minna Rahkola-Sorsa a , and Priit Zingel c a Faculty of Biosciences, University of Joensuu, P.O. Box 111, FI-80101 Joensuu, Finland b Lammi Biological Station, University of Helsinki, FI-16900 Lammi, Finland c Estonian University of Life Sciences, Kreutzwaldi 64, 51014 Tartu, Estonia ! Corresponding author, [email protected] Received 15 May 2008 Abstract. The wastewaters of an iron mining company in NW Russia have changed the water quality in some forest lakes to be hard with a high pH, in contrast to the soft water and low pH in natural lakes. Two impacted lakes and a reference lake were sampled once in early August in three successive years for water quality, plankton communities, and fish. The concentrations of potassium, lithium, and sulphate were high in the impacted lakes. Total phosphorus was low (~ 10 ±g L °1 ) in all lakes. The primary producers² biomass and chlorophyll a content in the impacted lakes were high because of high densities of autotrophic picocyanobacteria ( Synechococcus spp.). All planktonic communities showed a changed taxa composition and lower species richness. Zooplankton was predominantly Rotatoria in all the lakes. In the impacted lakes, Cladocera was represented by Bosmina , and Copepoda by small cyclopoids. The most obvious substance to be harmful to some planktonic species was potassium. The high pH and high mineral content of the water obviously lower both the toxicity and the bioavailability of heavy metals in the impacted lakes. Key words: alkaline mining waste, picocyanobacteria, Synechococcus , phytoplankton, Ciliata, zoo- plankton. INTRODUCTION Industrial wastewaters often have harmful effects on recipient lakes. For example, acidic mine drainage with a low pH and high metal contents often causes serious ecological damage (e.g. Niinioja et al., 2003). Since 1984 the JSC Karelsky Okatysh mining company in the Kostomuksha area (64³43 N, 30³58 E) in Karelia, NW Russia, has extracted and processed magnetite ore into iron pellets (7.6 million tonnes in 2004). The company affects the environment by air pollution (SO 2 and dust) and alkaline wastewater emissions. Since 1994 wastewaters (approx. 10 20 million m 3 y °1 ; Lozovik et al., 2001) from a dammed basin and from open mining pits (2 3 million m 3 y °1 ) have been allowed to flow a distance of 75 km through a number of small lakes and the Kenti River to the larger lake Middle Kuito. Waste flow represents approximately 8% of the mean discharge of 8.21 m 3 s °1 (Kukharev et al., 1995) at the river outlet. Data on water quality and
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Pelagic food web in lakes affected by mining waste 215 biota in this water course have been given e.g. in Virtanen & Markkanen (2000), Lozovik et al. (2001), and Kalinkina et al. (2003). Preliminary results on the food web are given e.g. in Holopainen et al. (2003b).
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