Data from: Holocene environmental change in Rotsee and its impact on sedimentary carbon storage
Data files
Jul 25, 2025 version files 1.88 MB
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README.md
22.95 KB
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Rotsee_Data_File_Dryad_April30version_3.xlsx
1.85 MB
Abstract
To assess the long-term impact of climate change and human influence on lakes and their sedimentary carbon storage, paleo-environmental approaches using well-dated lake sediment cores can be employed. Here, we reconstruct carbon mass accumulation rates for organic and inorganic carbon since 13 ka BP in Rotsee, a perialpine lake near the Swiss Alps, using a 12m sediment core. A multiproxy approach (XRF, carbon and nitrogen isotopes, organic macromolecule chemical compositions, aDNA) was used to explore changes in the lake system that affect sedimentary carbon storage. The Early Holocene (11.8 to 7 cal ka BP) was characterized by a mixed phytoplankton and watershed-derived provenance of organic matter, and the deposition of inorganic and organic sedimentary carbon. Warming during the Holocene Thermal Maximum (9.8 to 8.8 cal ka BP) increased sedimentary carbon storage. In the mid-to-late Holocene (7 to 1 cal ka BP), the sedimentary record indicates an increased influx of allochthonous, vascular plant-derived organic matter, and low production or conservation of phytoplankton-derived carbon. Organic carbon storage increased, while inorganic carbon became negligible. Larger deforestation events, potentially during Neolithic times (around 4 ka BP), but especially during Roman times (2 ka BP), coincided with further increased organic carbon MARs. Recent sediments, influenced by eutrophication in the last century, show higher carbon accumulation rates compared to earlier Holocene periods. Rotsee serves as a case study of how climate warming and human land use changes have influenced lake development and sedimentary carbon storage, with broader implications for understanding carbon dynamics in high-altitude lakes and their future carbon balance.
https://doi.org/10.5061/dryad.jsxksn0mq
Description of the data and file structure
This datafile contains measured parameters on which the paleo-environmental reconstruction of a Swiss peri-alpine lake (Rotsee). Three short cores and two long cores were collected at a water depth of 5.5 m (47°04’27.81”N, 8°19’25.7”E WGS 84; 667230/214087 LV95) between 03/10/2021 and 05/10/2021.
This includes:
- the data on which the age model is based, and the results of the age model
- the measured dry bulk density values
- all available XRF scans, and the tie points used for establishing the composite core
- the values for bulk TOC, TN, d15N-TN and d13C-TOC values
- the relative abundance of macromolecular classes
- the gene copy count of 18S (Eukaryotes) and rbcL genes (Tracheophyta, Ochrophyta, Clorophyta).
Because of its long record of climate, vegetation, and anthropogenic changes, Rotsee sediments provide an excellent opportunity to investigate how these changes affect the long-term burial and preservation of sedimentary carbon pools. Based on a multiproxy approach we here test the hypothesis that climate warming from the Late Glacial to the early Holocene contributed to an increase in trophic state, primary productivity, and associated organic carbon burial rates in Rotsee.
Files and variables
File: Rotsee_Data_File_Dryad_April30version_3.xlsx
Description: Tab 1 - XRF_*longcore_*1. For the first borehole, the elemental composition of the sediments has been described using XRF core scanning. Resolution is 1 cm. Results expressed as counts per second (cps), and both the average value and the stdev (std) is reported.
Variables
- Core.section.ROT21-1-X (3m length) - Number of 3m long core sections, going from 1-5, from shallow to deeper sediments. Where infill was identified, the sediment layer that represent infill, at the top of each section, was removed.
- Core.subsection (1m length) - After retrieving the 3m core sections, they were cut in 1m sections before lengthwise splitting.
- Depth.in.core.section.(cm) - from the top of each 3m core liner, this represents the measured depth in each section.
- Composite.Sediment.depth.(cm blf) - depth based on the assembled composite core, after correlating of borehole 1 and 2. This depth is used throughout the manuscript for plots.
- Mg (cps) - Magnesium (counts per second)
- Mg Std (cps) - Magnesium standard deviation (counts per second)
- Al (cps) - Aluminium (counts per second)
- Al Std (cps) - Aluminium standard deviation (counts per second)
- Si (cps) - Silica (counts per second)
- Si Std (cps) - Silica standard deviation (counts per second)
- P (cps) - Phosphorus (counts per second)
- P Std (cps) - Phosphorus standard deviation (counts per second)
- S (cps) - Sulphur (counts per second)
- S Std (cps) - Sulphur standard deviation (counts per second)
- Cl (cps) - Chloride (counts per second)
- Cl Std (cps) - Chloride standard deviation (counts per second)
- Ar (cps) - Argon (counts per second)
- Ar Std (cps) - Argon standard deviation (counts per second)
- K (cps) - Potassium (counts per second)
- K Std (cps) - Potassium standard deviation (counts per second)
- Ca (cps) - Calcium (counts per second)
- Ca Std (cps) - Calcium standard deviation (counts per second)
- Ti (cps) - Titanium (counts per second)
- Ti Std (cps) - Titanium standard deviation (counts per second)
- V (cps) - Vanadium (counts per second)
- V Std (cps) - Vanadium standard deviation (counts per second)
- Cr (cps) - Chromium (counts per second)
- Cr Std (cps) - Chromium standard deviation (counts per second)
- Mn (cps) - Manganese (counts per second)
- Mn Std (cps) - Manganese standard deviation (counts per second)
- Fe (cps) - Iron (counts per second)
- Fe Std (cps) - Iron standard deviation (counts per second)
- Co (cps) - Cobalt (counts per second)
- Co Std (cps) - Cobalt standard deviation (counts per second)
- Ni (cps) - Nickel (counts per second)
- Ni Std (cps) - Nickel standard deviation (counts per second)
- Cu (cps) - Copper (counts per second)
- Cu Std (cps) - Copper standard deviation (counts per second)
- Zn (cps) - Zinc (counts per second)
- Zn Std (cps) - Zinc standard deviation (counts per second)
- Ga (cps) - Gallium (counts per second)
- Ga Std (cps) - Gallium standard deviation (counts per second)
- As (cps) - Arsenic (counts per second)
- As Std (cps) - Arsenic standard deviation (counts per second)
- Br (cps) - Bromine (counts per second)
- Br Std (cps) - Bromine standard deviation (counts per second)
- Rb (cps) - Rubidium (counts per second)
- Rb Std (cps) - Rubidium standard deviation (counts per second)
- Sr (cps) - Strontium (counts per second)
- Sr Std (cps) - Strontium standard deviation (counts per second)
- Y (cps) - Yttrium (counts per second)
- Y Std (cps) - Yttrium standard deviation (counts per second)
- Zr (cps) - Zirconium (counts per second)
- Zr Std (cps) - Zirconium standard deviation (counts per second)
- Mo (cps) - Molybdenum (counts per second)
- Mo Std (cps) - Molybdenum standard deviation (counts per second)
- Rh Ka Inc (cps) - Rhodium (Rh) K-alpha incoherent scatter (counts per second)
- Rh Ka Inc Std (cps) - Rhodium (Rh) K-alpha incoherent scatter, standard deviation (counts per second)
- Rh Ka Coh (cps) - Rhodium (Rh) K-alpha coherent scatter (counts per second)
- Rh Ka Coh Std (cps) - Rhodium (Rh) K-alpha coherent scatter, standard deviation (counts per second)
- Pb (cps) - Lead (counts per second)
- Pb Std (cps) - Lead standard deviation (counts per second)
- U (cps) - Uranium (counts per second)
- U Std (cps) - Uranium standard deviation (counts per second)
Description: Tab 2 - XRF_*longcore_*2. For the second borehole, the elemental composition of the sediments has been described using XRF core scanning. Resolution is 1 cm. Results expressed as counts per second (cps), and both the average value and the stdev (std) is reported.
Variables
- Core.section.ROT21-1-X (3m length) - Number of 3m long core sections, going from 1-5, from shallow to deeper sediments. Where infill was identified, the sediment layer that represent infill, at the top of each section, was removed.
- Core.subsection (1m length) - After retrieving the 3m core sections, they were cut in 1m sections before lengthwise splitting.
- Depth.in.core.section.(cm) - from the top of each 3m core liner, this represents the measured depth in each section.
- Composite.Sediment.depth.(cm blf) - depth based on the assembled composite core, after correlating of borehole 1 and 2. This depth is used throughout the manuscript for plots.
- Mg (cps) - Magnesium (counts per second)
- Mg Std (cps) - Magnesium standard deviation (counts per second)
- Al (cps) - Aluminium (counts per second)
- Al Std (cps) - Aluminium standard deviation (counts per second)
- Si (cps) - Silica (counts per second)
- Si Std (cps) - Silica standard deviation (counts per second)
- P (cps) - Phosphorus (counts per second)
- P Std (cps) - Phosphorus standard deviation (counts per second)
- S (cps) - Sulphur (counts per second)
- S Std (cps) - Sulphur standard deviation (counts per second)
- Cl (cps) - Chloride (counts per second)
- Cl Std (cps) - Chloride standard deviation (counts per second)
- Ar (cps) - Argon (counts per second)
- Ar Std (cps) - Argon standard deviation (counts per second)
- K (cps) - Potassium (counts per second)
- K Std (cps) - Potassium standard deviation (counts per second)
- Ca (cps) - Calcium (counts per second)
- Ca Std (cps) - Calcium standard deviation (counts per second)
- Ti (cps) - Titanium (counts per second)
- Ti Std (cps) - Titanium standard deviation (counts per second)
- V (cps) - Vanadium (counts per second)
- V Std (cps) - Vanadium standard deviation (counts per second)
- Cr (cps) - Chromium (counts per second)
- Cr Std (cps) - Chromium standard deviation (counts per second)
- Mn (cps) - Manganese (counts per second)
- Mn Std (cps) - Manganese standard deviation (counts per second)
- Fe (cps) - Iron (counts per second)
- Fe Std (cps) - Iron standard deviation (counts per second)
- Co (cps) - Cobalt (counts per second)
- Co Std (cps) - Cobalt standard deviation (counts per second)
- Ni (cps) - Nickel (counts per second)
- Ni Std (cps) - Nickel standard deviation (counts per second)
- Cu (cps) - Copper (counts per second)
- Cu Std (cps) - Copper standard deviation (counts per second)
- Zn (cps) - Zinc (counts per second)
- Zn Std (cps) - Zinc standard deviation (counts per second)
- Ga (cps) - Gallium (counts per second)
- Ga Std (cps) - Gallium standard deviation (counts per second)
- As (cps) - Arsenic (counts per second)
- As Std (cps) - Arsenic standard deviation (counts per second)
- Br (cps) - Bromine (counts per second)
- Br Std (cps) - Bromine standard deviation (counts per second)
- Rb (cps) - Rubidium (counts per second)
- Rb Std (cps) - Rubidium standard deviation (counts per second)
- Sr (cps) - Strontium (counts per second)
- Sr Std (cps) - Strontium standard deviation (counts per second)
- Y (cps) - Yttrium (counts per second)
- Y Std (cps) - Yttrium standard deviation (counts per second)
- Zr (cps) - Zirconium (counts per second)
- Zr Std (cps) - Zirconium standard deviation (counts per second)
- Mo (cps) - Molybdenum (counts per second)
- Mo Std (cps) - Molybdenum standard deviation (counts per second)
- Rh Ka Inc (cps) - Rhodium (Rh) K-alpha incoherent scatter (counts per second)
- Rh Ka Inc Std (cps) - Rhodium (Rh) K-alpha incoherent scatter, standard deviation (counts per second)
- Rh Ka Coh (cps) - Rhodium (Rh) K-alpha coherent scatter (counts per second)
- Rh Ka Coh Std (cps) - Rhodium (Rh) K-alpha coherent scatter, standard deviation (counts per second)
- Pb (cps) - Lead (counts per second)
- Pb Std (cps) - Lead standard deviation (counts per second)
- U (cps) - Uranium (counts per second)
- U Std (cps) - Uranium standard deviation (counts per second)
Description: Tab 3 - XRF_shortcore
Variables
- Short core - name of shortcore, representing a single UWITEC gracity core with 9cm diameter
- Sample - Unit only relevant for laboratory analyst
- Sediment depth (mm), measured from the top of the core, which represents the undisturbed sediment surface.
- Mg Ka (cps) - Magnesium, K-alpha (Kα) X-ray emission (counts per second)
- Al Ka (cps) - Aluminium, K-alpha (Kα) X-ray emission (counts per second)
- Si Ka (cps) - Silica, K-alpha (Kα) X-ray emission (counts per second)
- P Ka (cps) - Phosphorus, K-alpha (Kα) X-ray emission (counts per second)
- S Ka (cps) - Sulphur, K-alpha (Kα) X-ray emission (counts per second)
- Cl Ka (cps) - Chloride, K-alpha (Kα) X-ray emission (counts per second)
- Ar Ka (cps) - Argon, K-alpha (Kα) X-ray emission (counts per second)
- K Ka (cps) - Potassium, K-alpha (Kα) X-ray emission (counts per second)
- Ca Ka (cps) - Calcium, K-alpha (Kα) X-ray emission (counts per second)
- Ti Ka (cps) - Titanium, K-alpha (Kα) X-ray emission (counts per second)
- V Ka (cps) - Vanadium, K-alpha (Kα) X-ray emission (counts per second)
- Cr Ka (cps) - Chromium, K-alpha (Kα) X-ray emission (counts per second)
- Mn Ka (cps) - Manganese, K-alpha (Kα) X-ray emission (counts per second)
- Fe Ka (cps) - Iron, K-alpha (Kα) X-ray emission (counts per second)
- Co Ka (cps) - Cobalt, K-alpha (Kα) X-ray emission (counts per second)
- Ni Ka (cps) - Nickel, K-alpha (Kα) X-ray emission (counts per second)
- Cu Ka (cps) - Copper, K-alpha (Kα) X-ray emission (counts per second)
- Zn Ka (cps) - Zinc, K-alpha (Kα) X-ray emission (counts per second)
- Ga Ka (cps) - Gallium, K-alpha (Kα) X-ray emission (counts per second)
- As Ka (cps) - Arsenic, K-alpha (Kα) X-ray emission (counts per second)
- Br Ka (cps) - Bromine, K-alpha (Kα) X-ray emission (counts per second)
- Rb Ka (cps) - Rubdium, K-alpha (Kα) X-ray emission (counts per second)
- Sr Ka (cps) - Strontium, K-alpha (Kα) X-ray emission (counts per second)
- Y Ka (cps) - Yttrium, K-alpha (Kα) X-ray emission (counts per second)
- Zr Ka (cps) - Zirconium, K-alpha (Kα) X-ray emission (counts per second)
- Mo Ka (cps) - Molybdenum, K-alpha (Kα) X-ray emission (counts per second)
- Rh Ka Inc (cps) - Rhodium, K-alpha (Kα) X-ray incoherent emission (counts per second)
- Rh Ka Coh (cps) - Rhodium, K-alpha (Kα) X-ray coherent emission (counts per second)
- Pb La (cps) - Lead, L-alpha (Kα) X-ray emission (counts per second)
- U La (cps) - Uranium, L-alpha (Kα) X-ray emission (counts per second)
- Br Ka (cps) - Bromine, K-alpha (Kα) X-ray emission (counts per second)
- Rb Ka (cps) - Rubidium, K-alpha (Kα) X-ray emission (counts per second)
- Sr Ka (cps) - Strontium, K-alpha (Kα) X-ray emission (counts per second)
- Y Ka (cps) - Yttrium, K-alpha (Kα) X-ray emission (counts per second)
- Zr Ka (cps) - Zirconium, K-alpha (Kα) X-ray emission (counts per second)
- Mo Ka (cps) - Molybdenum, K-alpha (Kα) X-ray emission (counts per second)
- Rh Ka Coh (cps) - Rhodium, K-alpha (Kα) X-ray coherent emission (counts per second)
- Rh Ka Inc (cps) - Rhodium, K-alpha (Kα) X-ray incoherent emission (counts per second)
- Ag Ka Coh (cps) - Silver, K-alpha (Kα) X-ray incoherent emission (counts per second)
- I Ka (cps) - Iodine, K-alpha (Kα) X-ray incoherent emission (counts per second)
- Ba Ka (cps) - Barium, K-alpha (Kα) X-ray incoherent emission (counts per second)
Description: Tab 4 - Tie points. This outlines the tie points that are selected on the XRF trace of each borehole, to allow establishing the composite core.
Variables
- Two tables, each row shows the corresponding depths (core section depth) where XRF traces allowed to determined corresponding sedimentary layer in Core Hole 1 and Core Hole 2.
Description: Tab 5 - Data used for rplum age model. Has both 14C and Cs ages of discrete sample depths "Data 14C ages that were suplemented to the rplum model", and 210Pb values measured on shortcore 'Data rplum model'.
Variables: Data 14C ages that were suplemented to the rplum model
- Sample LABEL. Either name of sample (form: 1_A_45 for samples , ROT21-9C-01), or Cs, which is the depth of an observed peak in Cs.
- Type: whether it concerns a plant macroremain (POC), or a macrophyte macroremain (Aq POC).
- Age: for POC sample type: non-calibrated 14C age. For AqPOC sample type: non-calibrated 14C age corrected for the reservoir age. For Cs peak samples: the ages of the Cs peaks before 2024: 35 and 58 year
- Error: for POC sample: measurement error on 14C age. For AqPOC sample type: propagated measurement errors (including error ass. with reservoir effect).
- Depth: sediment depth in composite core (cm below lake floor)
Variables: Data rplum model
- labID: sample ID in shortcore
- depth (cm below lake floor)
- density (parameterized, g.cm-3)
- 210Pb activity concentration (Bq/kg)
- 210Pb activity concentration, standard deviation (Bq/kg)
- thickness of sediment layer measured (cm)
- 226Ra activity concentration (Bq/kg)
- 226Ra activity concentration, standard deviation (Bq/kg)
- Settings: parameters to set the rplum model, including the year of 210Pb and 226Ra measurements
Description: Tab 6 - Output from rplum age model, which links the composite sediment depth (cm blf) to the modelled age of the sediments.
Variables
- depth (cm blf)
- mean age before 2024
- mean age BP (BP = 1950)
- standard deviation based on rplum model output (a)
Description: Tab 7 - Dry bulk density measurements, based on the weight of a known volume of sample, after drying.
Variables
- core or core section
- LABEL
- Depth in core (boundaries) in cm
- Comp_depth_mean (cm blf)
- Comp_depth Acc Note (1= sample on composite core, 2= sample not on composite core, composite depth based on extrapolation)
- DBD (g*cm-3)
- Age (cal a BP), NA indicates that the sample falls outside of the dated depth range
- Standard deviation age (a), NA indicates that the sample falls outside of the dated depth range
Description: Tab 8 - Bulk carbon and nitrogen parameters
Variables
- Sample LABEL
- Depth boundaries (cm blf)
- Average composite sediment depth (cm blf)
- Comp_depth Acc Note (1= sample on composite core, 2= sample not on composite core, composite depth based on extrapolation)
- d15N TN (%), stable nitrogen isotope of the total nitrogen
- d13C TOC (%), stable carbon isotope of the total organic carbon
- TOC (%) - weight percentage of total organic carbon
- TIC (%) - weight percentage of total inorganic carbon
- Mean Age (cal a BP), NA indicates that the sample falls outside of the dated depth range
- Age Std (a), NA indicates that the sample falls outside of the dated depth range
Description: Tab 9 - Pyrolysis GC/MS macromolecular composition
Variables
-
Sample LABEL - only relevant for analyst
-
Sediment depth (cm blf) - sediment depth on composite core
-
Comp_depth Acc Note (1= sample on composite core, 2= sample not on composite core, composite depth based on extrapolation)
-
carbohydrate (%)
Furfural Furan, 2,3-dihydro-2,5-dimethyl- 2-Furancarboxaldehyde, 5-methyl- 2-Furancarboxaldehyde, 5-methyl- 2-Cyclohexen-1-one, 4-hydroxy- 4-hydroxy-5,6-dihydro(2H)-pyran-2-one D-Limonene Dianhydrorhamnose Benzofuran, 2,3-dihydro- 3-Acetamidofuran Methyl-α-d-ribofuranoside 1,6-Anhydro-β-d-talopyranose Levoglucosan Methyl N-acetyl-d-glucosamide -
N.compounds (%)
1H-Pyrrole-2,5-dione Benzyl nitrile 3-Pyridinol, 6-methyl- Benzenepropanenitrile Indole Diketodipyrrole cis-Cyclo(L-Ala-L-Pro) Cyclo(Pro-Gly) Cyclo(Pro-Pro) Alkylamide2 Cyclo(Pro-Lys-NH3) 1H-Pyrrole, 3-methyl- dl-α-Methylglutamic acid 4(3H)-Pyrimidinone, 3-methyl- -
chlorophyll (%) - Prist-1-ene
-
fatty.acids (%) -
2-Pentenoic acid (C5:1) n-Hexadecanoic acid (C16:0) Octadecanoic acid (C18:0) 2-Heptadecanone (C17:1) -
alkanes (%) - Heneicosane (C22:0)
-
alkene (%) -
6-Tridecene (C13:1) 1-Docosene (C22:1) -
alcohols (%) -
1-Dodecanol, 2-hexyl- (C18:0) Behenic alcohol Ethanol, 2-(octadecyloxy)- -
aldehydes (%) - Tetradecanal
-
ketone (%) -
2-Heptadecanone (C17:1) 2-Pentadecanone 2-Nonadecanone -
ester (%) -
Decanoic acid, decyl ester Dodecanoic acid, tetradecyl ester Decanoic acid, decyl ester Dodecanoic acid, tetradecyl ester Dodecanoic acid, hexadecyl ester Dodecanoic acid, tetradecyl ester Tetradecanoic acid, hexadecyl ester -
hopane (%) -
22,29,30 trisnorhop17(21)-ene Urs-20-en-16-one -
sterane (%) -
Cholesta-3,5-diene Stigmastan-3,5-diene -
PAHs (%) -
p-Xylene Ethanone, 2,2-dihydroxy-1-phenyl- 1H-Indole, 3-methyl- 2H-1-Benzopyran-3,4-diol, 2-(3,4-dimethoxyphenyl)-3,4-dihydro-6-methyl-, (2α,3α,4α)- Butan-2-one, 4-(3-hydroxy-2-methoxyphenyl)- -
phenol (%) -
Phenol p-Cresol Phenol, 2-methoxy- Phenol, 3-ethyl- Creosol Phenol, 4-ethyl-2-methoxy- 2-Methoxy-4-vinylphenol Phenol, 2,6-dimethoxy- Phenol, 2-methoxy-5-(1-propenyl)-, (E)- Phenol, 2-methoxy-4-(1-propenyl)- Phenol, 2,6-dimethoxy-4-(2-propenyl)- 4-((1E)-3-Hydroxy-1-propenyl)-2-methoxyphenol -
lignin (%) - Syringaldehyde
-
others (%) -
Friedelan-3-one γ-Tocopherol -
Mean Age (cal a BP), NA indicates that the sample falls outside of the dated depth range
-
Age Std (a), NA indicates that the sample falls outside of the dated depth range
Description: Tab 10 - Pyrolysis GC/MS sugarcomposition
Variables
- Sample LABEL
- Sediment depth (cm blf)
- Comp_depth Acc Note (1= sample on composite core, 2= sample not on composite core, composite depth based on extrapolation)
- Levosugar - Levoglucosan and 1,6-Anhydro-β-d-talopyranose
- (alkyl)furans and furanones - Furfural; Furan, 2,3-dihydro-2,5-dimethyl-; 2-Furancarboxaldehyde, 5-methyl-;2-Furancarboxaldehyde, 5-methyl-; Benzofuran, 2,3-dihydro-
- pyrans - 4-hydroxy-5,6-dihydro(2H)-pyran-2-one
- chitin.derived - 3-Acetamidofuran and Methyl N-acetyl-d-glucosamide
- Methyl-α-d-ribofuranoside
- Dianhydrorhamnose
- other - 4-hydroxy-2-Cyclohexen-1-one and D-Limonene
- Mean Age (cal a BP), NA indicates that the sample falls outside of the dated depth range
- Age Std (a), NA indicates that the sample falls outside of the dated depth range
Description: Tab 11 - aDNA gene counts
Variables
- Sample LABEL
- Sediment depth (cm blf)
- Comp_depth Acc Note (1= sample on composite core, 2= sample not on composite core, composite depth based on extrapolation)
- 18S rRNA gene copy number
- Stdev 18S rRNA gene copy number
- Average Tracheophyta rcbL gene copy number
- Stdev Tracheophyta rcbL gene copy number
- Average Chlorophyta rcbL gene copy number
- Stdev Chlorophyta rcbL gene copy number
- Average Ochrophyta rcbL gene copy number
- Stdev Ochrophyta rcbL gene copy number
- Mean Age (cal a BP), NA indicates that the sample falls outside of the dated depth range
- Age Std (a), NA indicates that the sample falls outside of the dated depth range
- for rcbL gene copy number: b.d.l. indicates that the amount of DNA extracted was below detection limit. NA indicates that the standard deviation could not be calculated, as no duplicate was present.
Core collection and on-site subsampling
Three short cores and two long cores were collected at a water depth of 5.5 m (47°04’27.81”N, 8°19’25.7”E WGS 84; 667230/214087 LV95) between 03/10/2021 and 05/10/2021. The short cores (40-60 cm long) were collected from a vessel using a gravity corer with clear plastic liners (UWITEC; inner liner diameter 90 mm). The two long cores (sections ROT21-1-1 to ROT21-1-5 and ROT21-1-6 to ROT21-1-9) were taken 4 m apart from each other, using a shoreline moored platform using a piston coring system with a manual hammer, without a re-entry cone (UWITEC; inner liner diameter: 59.5 mm). Long cores were taken in sections of 3 m (except for 1 section that was 2 m). The recovery of two parallel long cores, vertically offset by one meter, was necessary to obtain a high-quality, complete sedimentary sequence. All short and long cores were brought onshore for sampling immediately after core recovery. Short cores were maintained in vertical position and sampled by extrusion, whereas long cores were first accessed horizontally through ‘windows’ that were cut into the core liner. From each depth sampled, sediments for determination of porosity and bulk density, DNA analyses and macromolecular organic matter analyses were collected with sterile cut-off syringes. Samples for DNA extraction were immediately frozen in liquid N2, before storage at -80 °C, whereas samples for organic matter analysis were frozen and stored at -20 °C. Afterwards, the core sections were split lengthwise before subsampling 2 cm slots for bulk carbon and nitrogen analyses using solvent cleaned spatulas. One core half (the so-called archive half) remained intact for imaging and XRF scanning.
XRF scanning
Elemental compositions were measured at 5 mm resolution using a µXRF core scanner (Avaatech XRF) with an Oxford 100 W X-Ray tube and a rhodium anode equipped with a Canberra X - PIPS/DSA 1000 (MCA) detector. Prior to analysis, core surfaces were flattened to ensure uniform scanning and covered with 4 µm Ultralene foil. Elemental groups with lower energy levels were measured at 10 kV (1500 A, no filter, 15 s exposure), while mid-energy groups were measured at 30 kV (2000 A, Pd thin filter, 40 s exposure). Prior to determining the variability in XRF parameters (excluding Mo, Ar and coherent and incoherent scatter) using a principal component analysis (Supp. Fig. 1), the cps counts were transformed using a centered log-ratio transformation (Bertrand et al., 2024) and scaled. Based on untransformed cps counts (Supp. Fig. 2), selected XRF log-ratios were calculated.
Dating and age model
The top 50 cm of a short core was sectioned at 1 cm resolution and used for 210Pb and 137Cs dating (Fig. 1A; Supp. Table 1A). 137Cs peaks were determined to date the sediment layers deposited in 1987 and 1963 Anno Domini (AD). In addition, radiocarbon dating on 19 macrofossils, including 12 seeds, leaf remains and twigs of terrestrial plants, and 7 macrodetrital remains of aquatic macrophytes was performed (Fig. 1B, Supp. Table 1B). After wet sieving, macrofossils were subjected to an acid-alkali-acid treatment at room temperature (Norris et al. 2020) to remove carbonates, acid soluble humic material, and humic acids. At two depths, bulk sediments were acidified using fumigation (described in Haas et al. 2019) and weighed in for 14C dating, with the aim of constraining the reservoir age during the Younger Dryas (Supp. Table 1C). The reservoir age was used to correct the uncalibrated 14C ages measured on the aquatic macrophytes. 14C measurements were carried out on an Accelerator Mass Spectrometer (AMS) with an Elemental Analyzer unit (EA) using the MIni CArbon DAting System (MICADAS) at the Laboratory for Ion Beam Physics of the Eidgenössische Technische Hochschule (ETH) in Zurich. An age-depth model was created using rplum, which allows unsupported 210Pb values, 137Cs ages and uncalibrated 14C ages to be combined based on Bayesian statistics (Blaauw and Christen 2011). Radon measurements are available as estimates of supported 210Pb, assumed constant by the model. A memory strength of 10 and memory mean of 0.5 is used. In this model, 14C ages are converted to calendar ages using the INtCal20 calibration curve (Reimer et al. 2020).
Bulk nitrogen and carbon content and isotopes
Sediments were freeze-dried and homogenized using an agate mortar and pestle. Total nitrogen (%; TN) and δ15N-TN values were determined on between 3 to 200 mg of unacidified sediments using an EA-IRMS system composed of a Vario Pyro Cube coupled to a Isoprime 100 IRMS (Elementar, Germany). Repeated measurement of reference materials Acetanilide #1 (Schimmelmann, USA, δ15N = +1.18 ± 0.02) and High Organic Sediment Standard (HEKAtech, Germany, δ15N = +4.32 ± 0.20) were used to determine the instrument precision, which was determined to be generally below 0.05 ‰ δ15N for the Acetanilide standard, and below 0.07 ‰ δ15N for the sediment standard. Offsets between the measured and known δ15N values of the Acetanilide standard (average offset = 0.19 ± 0.08) were used to correct the δ15N-TN values of the bulk sediments. The contents of total carbon (TC), total organic (TOC) and total inorganic (TIC) carbon were measured on 50 mg of sample weighed into a ceramic crucible, on the SoliTOC® Cube (Elementar Analysensysteme, Germany). The reported TOC is the summed amounts of TOC400 and refractory organic carbon (ROC), with TOC400 determined at 400 °C and ROC between 400 °C and 600 °C, and TIC between 600 °C and 900 °C. Low (B2152) and high organic carbon content standards (B2150) from Elemental Microanalysis (United Kingdom) were run with each batch to determine the instrument accuracy, which was determined to be 98.9 ± 0.6%. δ13C-TOC of bulk sediments was measured on an EA-IRMS system, EA Vario Pyro Cube (Elementar Analysensysteme, Germany) and Isoprime IRMS (GV Instruments, UK), after acidification. For acidification, samples with inorganic carbon were subjected to a 1N HCl treatment until no more visible reaction occurred. To calibrate the instrument an Acetanilide #1 (Schimmelmann, USA, δ13C = -29.52 ± 0.01) standard was used, as well as a High Organic Content Sediment (SA990894; δ13C = -28.85 ± 0.10) and Low Organic Soil (SA33802152; δ13C = -22.88 ± 0.10) standards from Hekatech Analytics. In general, instrument precision during the runs was below 0.06 ‰ δ13C for Acetanilide and below 0.16 ‰ δ13C for the sediment and soil standard, and an accuracy better than 0.02 for δ13C for Acetanilide and 0.1 ‰ δ13C for the sediment and soil standard. No corrections of the δ13C values were performed.
Bulk compound classes and hydrocarbons
To determine the OM macro-molecular composition, pyrolysis gas chromatography mass spectrometry was used, following the set-up as described in Gajendra et al. 2023. Between 100 - 500 mg of freeze-dried sediments were weighed into autosampler containers (Eco-cup SF, Frontier Laboratories, Japan) and pyrolyzed at 450 °C and 650 °C, according to Tolu et al. (2015). The pyrolizer was connected to an autosampler (PY-2020iD and AS-1020E, FrontierLabs, Japan) and to a GC/MS system (Trace 1310, Thermo Scientific and ISQ 7000, Thermo Scientific) equipped with a DB-5MS capillary column (30 m x 0.25 mm i.d., 0.25 mm film thickness; J&W, Agilent Technologies AB, Sweden). Chromatograms were analyzed in R (version 2.15.2, 64 bits) based on a pipeline that identifies common mass fragments as pyrolysis products (Tolu et al. 2015). Pyrolysis products were then classified and annotated according to Tolu et al. (2015) and Ninnes et al. (2017). On average 27% of the total peak area occurred in peaks that didn’t provide conclusive structural information. Areas of individual compounds within each compound class were summed up (Supp. Table 2 for identity of individual compounds), and compound classes expressed as relative abundances (peak area of each compound class relative to total characterizable Py-GC/MS peak area). To summarize the main trends in compositional variability, a PCA was performed based on the standardized fractional abundance of the compound classes (Supp. Fig. 3).
Mass accumulation rates
Dry bulk density values, the mass (weight) of the dry solids divided by the total volume of the wet sample, were measured on 7 mL of sediments sampled with a cut-off syringe, based on weights before and after drying (n = 68). Using the linterp command from the astrochron package (Meyers 2014), the bulk dry density values were afterwards interpolated at a 1 cm resolution. Mass accumulation rates (MAR) were then calculated by multiplying the interpolated dry bulk density with measured weight percentages of TOC, TIC, and normalized per year, using a smoothed sedimentation rate (autoplot, smoothing with a smoothing width of 800, using the astrochron package; Meyers, 2014). Supp. Fig. 4 shows the variability of measured and interpolated parameters that are used to calculate the MAR values through time.
aDNA analysis
Sedimentary DNA was extracted according to Lysis Protocol I of Lever et al. 2015. Briefly, 0.2 g of sediment was added to 2-mL screw-cap tubes filled to 15 % with 0.1 mm Zr beads. For the vast majority of samples, 100 µl of 10 mM adenosine triphosphate (ATP; prepared by dissolving adenosine 5’-triphosphate disodium trihydrate in molecular grade water) solution was added to reduce DNA sorption. The only exceptions were deep glacial clay layers, in which recovery was significantly enhanced by increasing the ATP concentration to 300 mM. 0.5 ml of lysis solution I was added to all samples (Lever et al. 2015). Samples were then shaken for one hour at 50 °C (600 rpm; ThermoShaker, Eppendorf), and subsequently washed twice with cold 24:1 chloroform-isoamyl alcohol and precipitated with linear polyacrylamide (20 µg ml-1), 5 M sodium chloride and ethanol. The pellets were dried using a vacuum centrifuge (50 °C; Thermo Fisher Scientific, USA), resuspended in molecular grade water and purified with the CleanAll DNA/RNA Clean-up and Concentration Micro Kit (Norgen Biotek Corp., Canada; Protocol A). All extracts of samples and extraction negative controls (extraction blanks) were stored at -80 °C. Eukaryotic 18S rRNA and rbcL genes were quantified by real-time PCR (Lightcycler® 480; Roche) with SYBR®Green as dye. Eukaryotic 18S rRNA genes were amplified using the All18S primer pair (Deng et al. 2020), whereas chloroplast genes encoding the large subunit of ribulose-1,5bisphosphate carboxylase (rbcL) were quantified using published assays for vascular plants (Willerslev et al. 2003), Chlorophyta and Ochrophyta (both Han et al. 2022).