HR: 0800h
AN: PP11A-0207    [Abstracts]
TI: Chydorid Ephippia – a Promising Tool for Climate Reconstruction
AU: * Kultti, S
EM: seija.kultti@helsinki.fi
AF: Department of Geology University of Helsinki, P.O.Box 64, University of Helsin, 00014, Finland
AU: Sarmaja-Korjonen, K
EM: kaarina.sarmaja-korjonen@helsinki.fi
AF: Department of Geology University of Helsinki, P.O.Box 64, University of Helsin, 00014, Finland
AU: Nevalainen, L
EM: liisa.nevalainen@helsinki.fi
AF: Department of Geology University of Helsinki, P.O.Box 64, University of Helsin, 00014, Finland
AB: Ephippium analysis, a recent palaeolimnological method, uses the two reproduction strategies of littoral water fleas of the family Chydoridae (chydorids) to estimate the past length of open-water season in cold-temperate lakes. In northern lakes chydorids reproduce asexually during most of the open-water season until the oncoming winter triggers sexual reproduction. This results in the appearance of males and sexual females, and after fertilization, the formation of a modified female shell (carapace), the ephippium, which protects the resting eggs. Chitinous chydorid remains, including ephippia, preserve well in lake sediments and can be identified to species level. In a mild climate (long open-water season) the period of asexual reproduction is long compared to the period of sexual reproduction, resulting in a higher proportion of shells of asexual females being deposited in sediments than in cold climates where the proportion of ephippia (shells of sexual females) increases. Surface sediment samples were collected from 90 Finnish lakes. The lakes are situated along a transect across Finland where the average open-water season varies from 213 days in the south to 137 days in the north and where annual temperatures vary from +5° C to -2° C, respectively. We tested with statistical methods the relationship between the present ephippium proportions and the present climate normals (1970 – 2000). The preliminary results indicate a clear increase of ephippium proportions from N 60º to N 70º. The linear correlation is highest between ephippium proportion and June temperature (-0.84***). The aim of the study is to provide a model for climate reconstructions on the basis of the analysed data to be applied on past sediments
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting