Quantitative relationship between water-depth and sub-fossil ostracod assemblages in Lake Donggi Cona,Qinghai Province,China |
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Authors: | Steffen Mischke Ulrich Bößneck Bernhard Diekmann Ulrike Herzschuh Huijun Jin Annette Kramer Bernd Wünnemann Chengjun Zhang |
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Institution: | 1.Institute of Geological Sciences,Freie Universit?t Berlin,Berlin,Germany;2.Naturkundemuseum Erfurt,Erfurt,Germany;3.Alfred Wegener Institute for Polar and Marine Research, Research Unit Potsdam,Potsdam,Germany;4.State Key Laboratory of Frozen Soils Engineering, Cold and Arid Regions Environmental and Engineering Research Institute Lanzhou,Chinese Academy of Sciences,Lanzhou,China;5.School of Geography and Oceanography,Nanjing University,Nanjing,China;6.Lanzhou University, Centre for Arid Environment and Paleoclimate Research,Lanzhou,China |
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Abstract: | A calibration data set of 51 surface sediment samples from Lake Donggi Cona on the northeastern Tibetan Plateau was investigated
to study the relationship between sub-fossil ostracod assemblages and water depth. Samples were collected over a depth range
from 0.6 to 80 m. A total of 16 ostracod species was identified from the lake with about half of the species restricted to
the Tibetan Plateau and its adjacent mountain ranges and poorly known in terms of ecological preferences, and the other half
displaying a mainly Holarctic distribution. Living macrophytes and macroalgae were recorded in Lake Donggi Cona down to a
depth of about 30 m, and bivalve (Pisidium cf. zugmayeri) and gastropod (Gyraulus, Radix) shells were found down to depths of 43 and 48 m, respectively. The ostracod-water-depth relationship was assessed by multivariate
statistical analysis and ostracod-based transfer functions for water depth were constructed. Weighted averaging partial least
squares (WA-PLS) regression provided the best model with a coefficient of determination r
2 of 0.91 between measured and ostracod-inferred water depth, a root mean square error of prediction of 8% and a maximum bias
of 10.6% of the gradient length, as assessed by leave-one-out cross-validation. Our results show the potential of ostracods
as palaeo-depth indicators in appropriate settings. However, transfer-function applications using fossil ostracod assemblages
for palaeo-depth estimations require a thorough understanding of the palaeolimnological conditions of lakes and therefore
detailed multi-proxy analysis to avoid misinterpretation of ostracod-based inferences. |
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