Modern diatom, cladocera, chironomid, and chrysophyte cyst assemblages as quantitative indicators for the reconstruction of past environmental conditions in the Alps. II. Nutrients |
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| Authors: | André F Lotter H John B Birks Wolfgang Hofmann Aldo Marchetto |
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| Institution: | (1) Geobotanical Institute, University of Bern, Altenbergrain 21, CH-3013 Bern, Switzerland;(2) Swiss Federal Institute of Environmental Science and Technology (EAWAG), CH-8600 Dübendorf, Switzerland (e-mail;(3) Botanical Institute, University of Bergen, Allégaten 41, N-5007 Bergen, Norway;(4) Environmental Change Research Centre, Dept. of Geography, University College London, 26 Bedford Way, London, WC1H 0AP, UK (e-mail;(5) Max-Planck-Institut für Limnologie, August-Thienemann-Strasse 2, D-24302 Plön, Germany (e-mail;(6) Consiglio Nazionale delle Ricerche, Istituto Italiano di Idrobiologia, Largo Vittorio Tonolli, 50-52, I-28048 Verbania Pallanza, Italy (e-mail |
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| Abstract: | Surface sediments from 68 small lakes in the Alps and 9 well-dated sediment core samples that cover a gradient of total phosphorus (TP) concentrations of 6 to 520  g TP l-1 were studied for diatom, chrysophyte cyst, cladocera, and chironomid assemblages. Inference models for mean circulation log10 TP were developed for diatoms, chironomids, and benthic cladocera using weighted-averaging partial least squares. After screening for outliers, the final transfer functions have coefficients of determination (r2, as assessed by cross-validation, of 0.79 (diatoms), 0.68 (chironomids), and 0.49 (benthic cladocera). Planktonic cladocera and chrysophytes show very weak relationships to TP and no TP inference models were developed for these biota. Diatoms showed the best relationship with TP, whereas the other biota all have large secondary gradients, suggesting that variables other than TP have a strong influence on their composition and abundance. Comparison with other diatom – TP inference models shows that our model has high predictive power and a low root mean squared error of prediction, as assessed by cross-validation. |
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| Keywords: | transfer functions WA-PLS total phosphorus trophic state eutrophication surface sediments Switzerland diatoms cladocera chironomids chrysophytes |
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