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Late holocene water-level changes in lake iso lehmalampi, southern finland, reflected in subfossil cladocerans and chironomids

Nevalainen L., Luoto T.P., Sarmaja-Korjonen K.

Studia Quaternaria

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2008

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Vol. 25

33-42

EN

Analyses of subfossil cladocerans (Crustacea: Cladocera) and chironomids (Diptera: Chironomidae) were applied to examine water-level changes in a small and oligotrophic lake in southern Finland over the past 2000 years. Major changes in the invertebrate communities occurred ca. 400 AD onwards when the littoral cladoceran Alonella nana started to replace the planktonic Eubosmina as the dominant species and chironomids Psectrocladius sordidellus group and Zalutschia zalutschicola increased. These changes were most likely due to a decreasing water level and an enlarging proportion of the littoral area, providing suitable vegetative habitats, e.g. aquatic bryophytes (mosses), for these taxa. The lowering water level reached its minimum just before the Medieval Warm Period, ca. 800-1000 AD, after which the lake level rose again and remained high until modern times. A prominent change in the chironomid assemblages occurred during the 20th century when Ablabesmyia monilis and Chironomus anthracinus type increased, presumably due to changes in water chemistry, caused by anthropogenic load of pollutants.

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Holocene pattern of organic carbon accumulation in a small lake in Estonia

Punning Jaan_Mati, Koff Tiiu, Sakson Maire, Kangur Mihkel

Polish Journal of Ecology

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2007

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Vol. 55, nr 1

5-14

EN

A comprehensive study of the sediment profile of L. Viitna Linajarv, a small closed drainage lake located in northern Estonia (59 [deegres] 27.N, 25 [deegres] 01.E), was conducted to assess the impact of water-level changes on the carbon accumulation dynamics in the lake during the Holocene. The variations of the P content, C/N ratio, fossil pigments and diatom communities indicate essential changes in the lake ecosystem history during the Holocene. The results show that on millennial time-scale (10[^3] years) fluctuations of the lake level, concurrent shore erosion and coprecipitation of dissolved organic matter with allochthonous mineral particles were the driving factors in the lake history. Net organic carbon accumulation was [similar to] 30 g m[^-2] yr[^-1] at the beginning of the Holocene (ca 9000 BP), then decreased to 10 g m[^-1] yr[^-1] (5000-2000 BP) and increased in the upper layers (since 1000 BP) up to 60 g m[^-2] yr[^-1].

3

Recent sedimentation and eutrophication of kruklin lake after artificial drop in water-level in the middle of 19th century

Gąsiorowski M., Hercman H.

Studia Quaternaria

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2005

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Vol. 22

17-25

EN

Sediments of two short cores collected from two basins of Kruklin Lake were studied by means of 210Pb and Cladocera analyses. The 210Pb allowed to date sediments and was helpful to obtain changes of sedimentation rate during the last two centuries. The CRS model was applied to calculate sediments age. Sedimentation rate differed strongly (from 0.55 cm/yr to 6.25 cm/yr) not only in time, but also between each basin. An accurate chronology of sediments was the basis for tracking of palaeolimnological changes with Cladocera analysis. Cladoceran planktonic:littoral ratio reflects event of artificial drop of lake water-level in the middle of nineteenth century. However, this event was recorded only in sediments of the southern, shallower basin and we suggest, that cladoceran planktonic:littoral ratio is better representative in shallow lakes. Changes of Cladocera assemblage composition suggest also strong eutrophication of lake water during the last century.

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Ecosystem response to early and late Holocene lake-level changes in lake Jjuusa, Southern Estonia

Koff T., Punning J.-M., Sarmaja-Korjonen K., Martma T.

Polish Journal of Ecology

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2005

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Vol. 53, nr 4

553-570

EN

The main aim of the study is to analyse the response of the catchment and lake ecosystem to the lake-level change on the basis of pollen, macrofossil, cladoceran and stable isotope records obtained by a comprehensive study of sediments from a shore core from Lake Juusa (Southern Estonia). The obtained multi-proxy data indicate that there is good correspondence between lithological, macrofossil and cladoceran changes during most time in the studied period. The palaeorecords show that the development of the Lake Juusa ecosystem was triggered mainly by the fluctuations of the lake level. Discrepancies of the data for some periods are caused by the concurrent processes having specific impact on the obtained records.