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Evolution of an Eemian lake based on Cladocera analysis (Konin area, Central Poland)

Pawłowski D.

Acta Geologica Polonica

2011

Vol. 61, no. 4

441-450

The succession of Cladocera assemblages in the Eemian Sławoszewek palaeolake (Central Poland) and the inferred environmental parameters are presented. The Cladocera assemblages provide a rich and relatively complete record of the Cladocera succession of the Eemian Interglacial, and are similar to those from other Eemian sites in Poland. The species composition and the variability in frequency of specimens of Cladocera made it possible to distinguish five zones of their development, which correlate well with pollen data. The Sławoszewek palaeolake existed from the early Eemian to the late Eemian Interglacial; at the end of the middle Eemian, the lake dried up temporarily. The cladoceran assemblages show that the initial shallow, oligotrophic status of the lake was followed by an increase to eutrophic status, especially during the interglacial optimum. Based on cladoceran composition, changes in climatic conditions in the mid-pollen zone E1, the late pollen zone E5 and in pollen zone E7, were recognized. It appears that cladoceran development was due mainly to climate changes, but also to changes in the locally prevailing conditions within the water body. The high frequency of cladocerans and the presence of cladoceran taxa preferring warmer water in mid-pollen zone E1 show an increase in temperature. The appearance of cold-tolerant Cladocera species at the end of pollen zone E5, suggests unfavourable conditions, probably cooling. Changes in Cladocera patterns in pollen zone E7 show that warm conditions still obtained in this area.

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

2008

Vol. 56, nr 1

85-97

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.