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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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Description of the subfossil head shield of Alona protzi hartwig 1900 (anomopoda, chydoridae) and the environmental characteristics of its finding sites

Bjerring R., Nykanen M., Sarmaja-Korjonen K., Sinev A., Jensen K., Nevalainen L., Szeroczyńska K., Zawisza E.

Studia Quaternaria

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2008

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Vol. 25

47-53

EN

This paper gives a description of the head shield of Alona protzi, a rare species of Cladocera (water fleas) whose separated head shield has not yet been described in detail. Subfossil head shields of A. protzi were found in sediment cores taken from lakes in Denmark, Sweden, Finland, Estonia and Poland. Despite the rarity of the species this suggests a wide distribution of A. protzi in northern Europe. The ecology of A. protzi is poorly known. The environmental spectrum of the finding sites was wide and ranged from relatively nutrient poor clear water lakes to eutrophic turbid water lakes, indicating that A. protzi is not narrowly restricted. Most of the lakes were, however, meso-eutrophic with neutral to high pH, and with a relatively low abundance of submerged macrophytes. However, we cannot exclude the possibility that A. protzi mainly lives in groundwater and is only occasionally transported into lakes.

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Parthenogenesis and gamogenesis in seasonal succession of chydorids (Crustacea, Chydoridae) in three low-productive lakes as observed with activity traps

Nevalainen L.

Polish Journal of Ecology

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2008

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Vol. 56, nr 1

85-97

EN

The aim of the present study was to determine the variance in abundance of parthenogenetic (asexual) and gamogenetic (sexual) individuals among chydorids (Crustacea, Anomopoda, Chydoridae). The chydorids were monitored quantitatively with stationary activity traps in three lakes in southern Finland at 2-week intervals during the open-water season (early May-late October) in 2006. The lakes chosen for the study were low-productive forest lakes; Lake Kalatoin was dystrophic fish-free lake and lakes Tuhkuri and Iso Lehmalampi were oligotrophic. The abundance of trapped individuals varied widely among the lakes and during the sampling period presumably due to site-specific environmental conditions (available microhabitats, food, shelter). The abundance was highest in the dystrophic Lake Kalatoin (max. 43 x 10[^3] m[^2] trapday[^-1] in June) and clearly lower in the two oligotrophic lakes (max. 8.5 x 10[^3] m[^-2] trapday[^-1] in Lake Tuhkuri in mid-July and max. 2.2 x 10[^3] m[^-2] trapday[^1] in Lake Iso Lehmalampi in mid-October). The chydorids exhibited unique sexual reproduction patterns among sampling sites and populations as the abundance of trapped gamogenetic individuals differed, suggesting habitat- and population-specific patterns in gamogenesis. In lakes Kalatoin and Iso Lehmalampi gamogenetic individuals were caught in the traps during the autumn with maxima of 2.2 and 1.6 x 10[^3] m[^-2] trapday[^-1], respectively, but in Lake Tuhkuri no gamogenetic individuals were encountered during the autumn. Although Alonella nana (Baird) was most abundantly trapped species in all the lakes, its gamogenetic individuals were trapped numerously only in Lake Kalatoin (max. ca. 1.5 x l0[^3] m[^-2] trapday[^-1]). The results suggest that gamogenesis in chydorids is a more complex phenomenon than previously believed.

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Description of subfossil post-abdomen and post-abdominal claw of Ceriodaphnia (Cladocera, Daphniidae)

Nevalainen L.

Studia Quaternaria

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2007

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Vol. 24

65-68

EN

Cladoceran remains preserve selectively in lake sediments. Possibly all Cladocera species leave at least some identifiable remains in lake sediments. Exosceletal body parts of families Chydoridae and Bosminidae preserve best but other families are only variably represented in sediments by their outer body parts. Identification of all possible remains helps to achieve more precise palaeolimnological reconstruction of past ecosystems by Cladocera analysis. This article describes, together with photograph and line drawing the subfossil post-abdomen and post-abdominal claw of Ceriodaphnia, previously not widely identified.

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Identification of subfossil remains of cladocerans Latona setifera, Diaphanosoma brachyurum AND Holopedium gibberum

Nevalainen L., Sarmaja-Korjonen K.

Studia Quaternaria

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2005

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Vol. 22

41-44

EN

The preservation of chitinous outer body parts of Cladocera is mostly selective, except in two families, the planktonic Bosminidae and the littoral Chydoridae. In addition, at least some body parts of several other genera and taxa preserze but many of them have not been widely identified. The aim of the article is to present photographs and line drawings of the postabdomen and the postabdominal claws of Holopedium gibberum, together with the postabdominal claws of Latona setifera and Diaphanosoma brachyurum for use of cladoceran analysts. In analysis of subfossil remains pictures and descriptions of separate body parts make the identification more reliable. It is hoped that with increasing knowledge about remains of as many taxa as possible, a more complete picture of the past cladoceran assemblages can be obtained, together with a more precise assessment of past ecological conditions, such as pH and trophic state.