Biogeochemical variability during the past 3.6 million years recorded by FTIR spectroscopy in the sediment record of Lake El'gygytgyn, Far East Russian Arctic

C Meyer-Jacob,M Melles,V Wennrich,A C Gebhardt,P Rosén,H Vogel

doi:10.5194/cp-10-209-2014

Abstract

Abstract. A number of studies have shown that Fourier transform infrared spectroscopy (FTIRS) can be applied to quantitatively assess lacustrine sediment constituents. In this study, we developed calibration models based on FTIRS for the quantitative determination of biogenic silica (BSi; n = 420; gradient: 0.9–56.5%), total organic carbon (TOC; n = 309; gradient: 0–2.9%), and total inorganic carbon (TIC; n= 152; gradient: 0–0.4%) in a 318 m-long sediment record with a basal age of 3.6 million years from Lake El'gygytgyn, Far East Russian Arctic. The developed partial least squares (PLS) regression models yield high cross-validated (CV) R2CV = 0.86–0.91 and low root mean square error of cross-validation (RMSECV) (3.1–7.0% of the gradient for the different properties). By applying these models to 6771 samples from the entire sediment record, we obtained detailed insight into bioproductivity variations in Lake El'gygytgyn throughout the middle to late Pliocene and Quaternary. High accumulation rates of BSi indicate a productivity maximum during the middle Pliocene (3.6–3.3 Ma), followed by gradually decreasing rates during the late Pliocene and Quaternary. The average BSi accumulation during the middle Pliocene was ~3 times higher than maximum accumulation rates during the past 1.5 million years. The indicated progressive deterioration of environmental and climatic conditions in the Siberian Arctic starting at ca. 3.3 Ma is consistent with the first occurrence of glacial periods and the finally complete establishment of glacial–interglacial cycles during the Quaternary.

Highlights

The understanding of past environmental changes is of particular importance to facilitate the prediction of the magnitude and the regional implications of future environmental changes, especially in view of an anthropogenically forced global warming (IPCC, 2007)
We developed calibration models based on Fourier transform infrared spectroscopy (FTIRS) for the quantitative determination of biogenic silica (BSi; n = 420; gradient: 0.9–56.5 %), total organic carbon (TOC; n = 309; gradient: 0–2.9 %), and total inorganic carbon (TIC; n = 152; gradient: 0–0.4 %) in a 318 m-long sediment record with a basal age of 3.6 million years from Lake El’gygytgyn, Far East Russian Arctic
The developed models relating FTIR spectral information to conventional measurements for TOC, TIC and BSi show a good statistical performance for the 3.6 Myr-old sediment record of Lake El’gygytgyn. By applying these models in higher resolution to the sediment sequence, we obtained a detailed reconstruction of variations in the aquatic bioproductivity in Lake El’gygytgyn, which is primarily triggered by climate changes

Summary

Introduction

The understanding of past environmental changes is of particular importance to facilitate the prediction of the magnitude and the regional implications of future environmental changes, especially in view of an anthropogenically forced global warming (IPCC, 2007). Lake sediment records are valuable archives preserving these changes. Records such as those from Lake Baikal Williams et al, 1997), Lake Malawi Scholz et al, 2006) and Lake Biwa Fuji, 1988) extend several million years back in time and consist of several hundred metres of sediment. Multiproxy analyses of such long records are very time-consuming and cost-intensive. High-resolution sampling of these records can be restricted by the amount of sample material available for the different analyses

Methods

Results

Conclusion