CONTENTS & ABSTRACTS
In English. Summaries in Estonian
Proceedings of the Estonian Academy of Sciences.
Volume 51 No. 4 December 2002
Tracing the pathways of particles settling into a small lake; 227–241
Jaan-Mati Punning, Tiiu Koff, Tiiu Alliksaar, and Jaanus Terasmaa
Abstract. An inventory was made of the fluxes of dry matter, pollen grains, and spherical fly-ash particles into a small mesotrophic lake. The data obtained from a two-year experiment with regularly emptied sediment traps showed that the resuspension of settled particles in a lake of a low dynamic ratio depended mostly on the seasonal changes in the thermal stratification of the lake. The inventory of matter fluxes in the lake and to sediments during the last 4–5 years suggested that about 55% of the autochthonous organic matter would be decomposed during sedimentation. The sinking velocity of the studied particle types is low, especially so for pine pollen grains due to their morphological peculiarity.
Key words: particle fluxes, sediment traps, sedimentation, resuspension, small lake.
Pulsatilla patens and Pulsatilla pratensis (Ranunculaceae) in Estonia: distribution and ecology; 242–256
Indrek Pilt † and Ülle Kukk
Abstract. Despite the great changes in land use, the distribution of Pulsatilla patens and P. pratensis (Ranunculaceae) in Estonia, reconstructed using herbarium specimens and notes, was quite stable throughout the 20th century. Considering the data on the present sizes and habitat conditions of 29 P. patens and 34 P. pratensis populations, in our estimation, around a tenth of the territory of Estonia should, at the moment, be habitable for these species. Both species prefer well-lit locations, created by some disturbance such as fire, logging, etc. The temporal deterioration of habitats through overgrowing could be buffered to some extent by the long life span of adult plants. The main threatening factor is current logging practice, which causes severe contraction of populations.
Key words: Pulsatilla patens, Pulsatilla pratensis, distribution, population size, habitats, land use.
Phytobenthic microcoenoses along Estonian exposed seashores; 257–276
Triin Reitalu, Jaanus Paal, and Georg Martin
Abstract. Distribution and environmental range of phytobenthic microcoenoses along the exposed shores of the northeastern part of the Baltic Sea in Estonia are described. A total of 104 biomass samples were clustered into distinct micro-associations, and 35 composite samples into six community types. The Fucus vesiculosus community type is the most heterotoneous in the study area, including microcoenoses of various micro-associations. The other community types are more homotoneous. Phytobenthic microcoenoses at sites are related mainly to the depth of the seabed. Most of the microcoenoses have a more or less local distribution; only microcoenoses of the Fucus vesiculosus micro-association were found throughout the study area.
Key words: Baltic Sea, biomass, communities, distribution, micro-associations.
Feeding of herring in the Gulf of Finland in the 1970s–90s; 277–293
Ain Lankov and Henn Kukk
Abstract. In the 1980s–90s the feeding of pelagic fishes, including Baltic herring, changed due to altered hydrological conditions. The feeding intensity of herring decreased and its food spectrum shifted towards the energetically less valuable zooplankton. As a result, the mean body weight of herring decreased significantly. In the second half of the 1990s the process retarded and the weight of herring stabilized at the level of about 10 g lower than at the beginning of the 1970s. The annual food consumption of herring in the Gulf of Finland was the highest at the end of the 1980s, reaching 130 g m–2 (wwt). At the end of the 1990s it was 65–70 g m–2 (wwt). In the 1970s and in first half of the 1980s the annual metabolic rates constituted from 74.4 to 76.5% and the growth rate from 1.6 to 3.5% of the annual ration. In the second half of the 1980s and in the 1990s the amplitudes of metabolic and growth rates were restricted compared to the previous period (74.7–75.9% and 2.3–2.9%, respectively). In the 1990s the energy released for spawning rose, forming from 2.0 to 2.7% of the ration.
Key words: Baltic herring, annual consumption, food composition, feeding spectrum.
changes in the cytochrome P450 system of Baltic flounder from coastal waters of the Tallinn area in 1994–99; 294–302
Sergei Bogovski, Vladimir Muzyka, Boris Sergeyev, and
Abstract. In order to study effects of environmental contamination, a set of biomarkers were measured in livers of flounder (Platichthys flesus) from two urban sites and one nonurban reference site of the Gulf of Finland in the vicinity of Tallinn over the period 1994–99. The total cytochrome P450 (CYP) level and the activities of aryl hydrocarbon hydroxylase (AHH), 5-aminolevulinic acid synthetase (ALA-S), and heme synthetase (HEM-S) were quantified by means of spectrophotometry. For the flounder collected from the nonurban site, significant decreases of the AHH activity and the total CYP level were observed from 1994 to 1999 (p < 0.05). The activity of ALA-S decreased slightly and the activity of HEM-S increased over the study period. In one urban site, the activities of AHH and ALA-S, as well as the total level of CYP in flounder liver, were significantly higher in 1994 compared with 1999. HEM-S activities did not show any significant changes over this time period. In the other urban site AHH activities of flounder decreased slightly between 1996 and 1999, while the total CYP level diminished drastically over these years. The activities of HEM-S increased significantly during the period investigated, while the activities of ALA-S remained unchanged. These findings suggest that contamination of the marine environments by polycyclic aromatic hydrocarbons diminished everywhere in the Tallinn area during the study period. However, the results show that the area is still contaminated, as indicated by the elevated activity of heme synthesis enzymes and the total CYP content. Therefore, the monitoring of contaminants and their effects should be continued in this region.
Key words: marine pollution, flounder, cytochrome P450, aryl hydrocarbon hydroxylase, 5-aminolevulinate synthetase, heme synthetase.
Contents of volume 51; 303–304