Data for: Water depth and transparency drive the quantity and quality of organic matter in sediments of Alpine lakes on the Tibetan Plateau

The primary objectives of the study were to: (i) determine OM quantity and
quality in the sediments of alpine lakes on the Tibetan Plateau, (ii)
identify the primary environmental regulators of OM quantity and quality,
and (iii) reveal OM transformations in the water column and sediments.
Firstly, we collected sediments and lake water from 20 lakes with diverse
morphology and sizes across the entire Tibetan Plateau. Secondly, We
analyzed the bulk sedimentary OM and two leachable pools of the
sedimentary OM, i.e., water-soluble OM and alkaline-extracted OM combining
elemental and stable isotopic analysis, optical measurements (i.e.,
absorbance and fluorescence spectroscopy), and ultrahigh-resolution
molecular techniques (i.e., electrospray ionization-assisted Fourier
transform-ion cyclotron resonance mass spectrometry, ESI FT-ICR MS). We
also measured the lake water physicochemical characteristics (i.e., depth,
transparency, salinity, turbidity, DO, pH, TN, TP and Chl a), as well as
the composition of dissolved OM in water column via optical measurements.
Thirdly, we performed statistical analysis to determine the primary
environmental control and predictors of the spatial variability in
sedimentary OM on the Tibetan Plateau. The statistical analysis included
non-parametric Kruskal-Wallis with Dunn post hoc test, redundancy
analysis, and linear regression models. Main results of the study are that
(i) sedimentary water-soluble OM and alkaline-extracted OM were both
dominated by low-molecular-weight, low-aromaticity compounds with low
contributions of terrestrial humic substances, suggesting that sedimentary
leachable OM was primarily regulated by in-lake sources and processes;
(ii) water depth, water transparency, and total phosphorus concentration
in water column explained ~50% variance of sedimentary bulk and leachable
OM, substantiating the importance of autochthonous sources and primary
productivity in regulating the quantity and quality of sedimentary OM;
(iii) in comparison to lake surface water DOM, water-soluble OM and
alkaline-extracted OM from sediments had higher proportions of terrestrial
humic-like substances, suggesting preferential preservation of
allochthonous materials in the sediments.