Biomarkers record environmental changes along an altitudinal transect in the wettest place on Earth |
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| Institution: | 1. ETH Zürich, Department of Earth Sciences, 8092 Zürich, Switzerland;2. North-Eastern Hill University, Department of Geography, Shillong 793 022, India;1. Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, D-27515 Bremerhaven, Germany;2. MARUM Center for Marine Environmental Sciences, University of Bremen, D-28334 Bremen, Germany;1. Max-Planck-Institut für Biogeochemie, Jena, Germany;2. DFG-Leibniz Center for Surface Process and Climate Studies, Institut für Erd- und Umweltwissenschaften, Universität Potsdam, Germany;3. Faculté des Sciences, University of Maroua, Cameroon;4. National Herbarium of Cameroon, IRAD, Yaoundé, Cameroon;1. Institute of Geology and Mineralogy, University of Cologne, Germany;2. NIOZ Royal Netherlands Institute for Sea Research, Department of Marine Microbiology and Biogeochemistry, and Utrecht University, Den Burg, Texel, The Netherlands;3. Department of Earth Sciences, Faculty of Geosciences, Utrecht University, The Netherlands;4. Isotope Bioscience Laboratory - ISOFYS, Faculty of Bioscience Engineering, Ghent University, Belgium;5. MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany;1. MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Str., 28359 Bremen, Germany;2. Institute of Geosciences, University of São Paulo, Rua do Lago, 562, São Paulo, SP 05508-080, Brazil;3. School of Arts, Sciences and Humanities, University of São Paulo, Av. Arlindo Bettio 1000, São Paulo, SP 03828-000, Brazil;4. Alfred Wegener Institute – Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany;5. Center of Nuclear Energy in Agriculture, University of São Paulo, Av. Centenário 303, Piracicaba, SP 13400-970, Brazil;6. Division of Earth and Ocean Sciences, Duke University, Durham, NC 27708, USA;7. School of Geological Sciences and Engineering, Yachay Tech University, San Miguel de Urcuqui, Hacienda San Jose, Imbabura, Ecuador;1. Department of Earth Sciences, University of Southern California, Los Angeles, CA, USA;2. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA |
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| Abstract: | The combined application of plant wax δD (δDwax) and branched glycerol dialkyl glycerol tetraethers (brGDGTs) has been suggested as proxy for paleo-elevation. In some of the altitudinal transects studied so far, nonlinear precipitation gradients, large variations in seasonality, soil and vegetation types introduced substantial amounts of scatter in the relationship between these proxies and altitude. To further evaluate the principal functioning of the proxies, δDwax and brGDGTs were analysed in surface soils along an altitude gradient (from 28 m up to 1865 m a.s.l.) in Meghalaya, India. The transect experiences limited seasonal temperature variation and receives very high monsoonal precipitation along the whole elevation gradient. The δDwax show a significant relation with altitude (r2 = 0.72). The additional fits with stream water δD (r2 = 0.72) and modelled precipitation δD (r2 = 0.72) indicate that δDwax tracks the altitude effect on precipitation. Also the brGDGT distribution shows a correlation with altitude, reflecting the decrease in temperature with higher elevation (r2 = 0.65, or r2 = 0.66 using the original and recalibrated methylation of branched tetraethers-cyclisation of branched tetraethers (MBT–CBT) proxy). Application of the original MBT–CBT calibration generates calculated air temperatures that overestimate measured air temperature by ～6 °C, whereas temperatures similar to measured are obtained with the revised calibration. These results indicate that δDwax and brGDGTs may faithfully and accurately track environmental changes with altitude for transects where seasonal and diurnal temperature variability is relatively limited. Furthermore, proxy application to locations that experience high rainfall increases the suitability as climatic indicators, as it excludes soil moisture availability as a limiting factor. |
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