In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Biology. Ecology


Volume 50 No. 4 December 2001


Proceedings of the Estonian Academy of Sciences 50. Biology. Ecology; 227–230

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The influence of currents and waves on ecological conditions of the Väinameri; 231–247

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Abstract. Based on field measurements (1993–99) and hydrodynamic modelling the influence of currents on the ecological situation of the Väinameri is analysed and an introductory study on the resuspension is reported. 2D flow charts are presented. The Väinameri is a highly dynamic water body, where the situation is mostly determined by the water exchange processes forced by two major nearby basins (i.e., the Baltic Proper and the Gulf of Riga) and resuspension events during storms. The hydrophysical and hydrochemical front fluctuates in N–S direction and the local conditions are frequently overrun by these excursions. Resuspension events due to currents (in the straits) and surface waves (in the shallow parts of the Väinameri) affect the study area with high turbidity and cause an about 2–3-fold increase in phosphorus concentrations. On the basis of hydrodynamic behaviour two sub-basins could be defined in the Väinameri. The eastern part has about 85% of the water exchange, lower salinity, and higher nutrient concentrations. In the western section hydrological conditions are more marine and less variable.

Key words: currents, fronts, waves, resuspension, nutrients, modelling, Baltic Sea.

Vertical migrations of mysids in the Gulf of Riga; 248–255

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Ilmar KOTTA and Jonne KOTTA

Abstract. Vertical migrations of Mysis mixta, M. relicta, and Neomysis integer were studied in the north-eastern part of the Gulf of Riga during May–September 1999. All three mysid species performed diel vertical migrations. These migrations were more intense in late summer and autumn than in spring and early summer. The proportion of juveniles and small-sized adults (< 11 mm) in the vertical migrations was higher than that of adults. Usually N. integer appeared in the water column first in the evening, followed later by Mysis spp. Both Mysis spp., often referred to as cold stenotherms, were found in high abundance in the surface waters in spite of very strong temperature gradients.

Key words: Baltic Sea, distribution, Mysidacea, Mysis, Neomysis.

Transplantation experiment to study the development of mud-bottoms; 256–268

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Abstract. Mud-bottoms are formed in bogs after degeneration of Sphagnum mosses and vascular plants, their surface is formed by a dense algal mat. To control the hypothesis that factors causing the formation of mud-bottoms could be active in a restricted location during a relatively short period of time, a transplantation experiment was carried out in Männikjärve Bog, Central Estonia, in June 1997–October 2000. In 40 months the area of Sphagnum cuspidatum plots transplanted into the mud-bottom increased by 140–220% whereas the bare peat plots transplanted from mud-bottom into S. cuspidatum lawn overgrew almost entirely. The increase in the area of S. magellanicum plot transplanted into the mud-bottom from its other side was smaller (ca 80%), and the area of the bare peat plot transplanted into S. magellanicum lawn showed almost no change. Since the differences in the changes of plot areas could not be explained by ecological peculiarities of Sphagnum species involved, it was concluded that the factors causing the degeneration of sphagna and formation of mud-bottoms are of restricted distribution and short duration.

Key words: bare peat surface, bog microtopography, mud-bottom (hollow), revegetation, Sphagnum degeneration.

Water quality in the Pirita River, a raw water source for Tallinn; 269–278

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Rein RANNAMÄE and Ingeborg VELDRE

Abstract. The quality of the water of the Pirita River was evaluated on the ground of organo­leptical, chemical, and microbiological analyses. Background values of some water quality indicators in the Pirita River were often higher than in the Pirita–Ülemiste Canal. The oxygen regime in the river was favourable ensuring the required conditions for self-purification. The BOD7/PC ratio of the river water was low, which shows that natural biochemically stable substances dominate in the water. Phenols in the river water were of vegetable origin. The concentrations of oil products and detergents in the river water were at the level of the sensitivity of the relevant determination methods. From the point of view of environmental health the raw water of the Pirita River is safe to be directed into the distribution system of the Tallinn Water Treatment Plant.

Key words: river water, raw water, water quality, drinking water.

Seasonal dynamics of sugars in the leaves of Salix dasyclados and the effect of soil treatment with cement dust; 279–291

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Abstract. Cutting-derived Salix dasyclados Wimm. were grown on soil containing high amounts (2 kg m–2 in year 1 + 1 kg m–2 in year 2) of dust from filters of a cement plant. The pH of the treated soil was increased from 6.5 (control) to 7.6. Soluble sugars, starch, and chlorophylls in leaves of spring flush shoots were analysed during the vegetative growth of the second year of treatment. The lower hexose content in the leaves of treatment trees was approximately balanced by their higher sucrose content. Maltodextrins and starch were not affected significantly and no fructans were found. The effect of treatments on chlorophyll a and b was neglible. Total biomass was significantly lower than in control trees without any change in the partitioning of biomass between different parts of the trees.

Key words: alkaline soil, cement dust, chlorophyll, fructose, glucose, starch, sucrose.

Instructions to authors; 292–294

Contents of volume 50; 295–296