The results from a winter field study in 2009–2010 in Lake Vanajanselkä are presented. This lake is shallow, eutrophic, and annually ice-covered on average for 5 months. The ice sheet was 41–55 cm thick at the annual maximum, consisting of snow-ice and congelation ice. The e-folding depth of light intensity was 50–100 cm for congelation ice and 5–10 cm for snow. The water body had a 4-m thick upper mixed layer and lower continuously stratified layer. Fall cooling process was crucial to determine the temperature of the lower layer at freeze-up, anything within 0–4 °C. Oxygen concentration decreased in winter, especially close to the bottom sediments, and carbon dioxide concentration increased due to respiration activity. Phytoplankton production and biomass level were low or very low and, therefore, heterotrophic and mixotrophic species were abundant. Oxygen depletion in the hypolimnium had several chemical and ecological consequences, such as release of phosphorus from the bottom sediments. In spring, just before the ice-out, photosynthesis was at a high level beneath the ice due to improved light conditions and started to elevate the oxygen concentration in the topmost water layer.
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Research Article|
August 01 2012
The influence of ice season on the physical and ecological conditions in Lake Vanajanselkä, southern Finland
Matti Leppäranta;
Matti Leppäranta
1Department of Physics, University of Helsinki, Box 48 (Erik Palménin aukio 1), FI-00014 Helsinki, Finland E-mail: matti.lepparanta@helsinki.fi
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Anniina Heini;
Anniina Heini
1Department of Physics, University of Helsinki, Box 48 (Erik Palménin aukio 1), FI-00014 Helsinki, Finland E-mail: matti.lepparanta@helsinki.fi
2Lammi Biological Station, Pääjärventie 320, FI-16900 Lammi, Finland
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Elina Jaatinen;
Elina Jaatinen
1Department of Physics, University of Helsinki, Box 48 (Erik Palménin aukio 1), FI-00014 Helsinki, Finland E-mail: matti.lepparanta@helsinki.fi
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Lauri Arvola
Lauri Arvola
2Lammi Biological Station, Pääjärventie 320, FI-16900 Lammi, Finland
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Water Quality Research Journal (2012) 47 (3-4): 287–299.
Article history
Received:
January 17 2012
Accepted:
September 21 2012
Citation
Matti Leppäranta, Anniina Heini, Elina Jaatinen, Lauri Arvola; The influence of ice season on the physical and ecological conditions in Lake Vanajanselkä, southern Finland. Water Quality Research Journal 1 August 2012; 47 (3-4): 287–299. doi: https://doi.org/10.2166/wqrjc.2012.003
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