DOI: 10.5061/dryad.9s4mw6mrm
title: Algal lipid distributions and hydrogen isotope ratios reflect phytoplankton community dynamics in Rotsee (Switzerland)

description: Reconstructions of past changes in algal community composition provide
 important context for future alterations in biogeochemical cycling.
 However, many existing phytoplankton proxies are indicative of individual
 algal groups and are not fully representative of the whole community.
 Here, we evaluated hydrogen isotope ratios of algal lipids (δ2Hlipid) as a
 potential proxy for phytoplankton community composition. We sampled the
 water column of Rotsee, a small eutrophic lake in Switzerland, every
 second week from January 2019 to February 2020 and analyzed distributions
 and the relative offsets between δ2Hlipid values (ε2Lipid1/Lipid2) from
 short-chain fatty acids, phytosterols and phytol. Comparing these data
 with phytoplankton cell counts, we found ε2C16:0/sterol and
 ε2sterol/phytol values reflect shifts in the eukaryotic algal community.
 To assess whether the selected phytoplankton groups were the main sources
 of the selected lipids, we further modeled algal ε2Lipid1/Lipid2 values
 based on δ2HC16:0, δ2Hsterol and δ2Hphytol values from batch cultures of
 individual algal groups and their biovolume in Rotsee and evaluated the
 role of heterotrophy on ε2Lipid1/Lipid2 values using a model incorporating
 δ2HC16:0 and δ2Hsterol values from microzooplankton. Annually-integrated
 and amount-weighted ε2Lipid1/Lipid2 values measured in Rotsee were within
 6 to 17 ‰ of the mean of modeled algal ε2Lipid1/Lipid2 values,
 demonstrating a strong link with the phytoplankton community composition,
 while ε2Lipid1/Lipid2 values including microzooplankton lipids had a
 larger offset. Additionally, cyanobacterial biovolume was positively
 correlated with the ratio of phytol and phytosterols (phytol:sterol ratio)
 as well as the ratio of unsaturated C18 and C16:0 fatty acids (C18:C16
 ratio). Our results support the application of sedimentary ε2Lipid1/Lipid2
 values in eutrophic lakes as a proxy for past phytoplankton community
 assemblages. Moreover, the calculation of sedimentary phytol:sterol and
 C18:C16 ratios provides an additional proxy for reconstructing
 cyanobacterial blooms.
description: Water and biomass samples were taken biweekly from the water
 column of Rotsee at 1 m depth and the chlorophyll maximum depth over a
 one-year period. For biomass samples, lake water was filtered through
 glass fiber filters. The chlorophyll maximum depth on each sampling date
 was determined based on the turbidity maximum measured by a
 multi-parameter CTD probe. The temperature at the two different sampling
 depths was estimated by the mean of temperatures measured by the CTD probe
 from 0.5 m above to 0.5 m below the respective depth. Cell counts of
 phytoplankton and microzooplankton species were conducted from water
 samples and the biovolume of individual taxonomic groups was calculated
 based on cell densities and the mean per-cell biovolume.
 δ<sup>2</sup>H<sub>water </sub>values of filtered
 water samples were measured by a high-temperature conversion/elemental
 analyzer (TC/EA) coupled with isotope ratio mass spectrometry (IRMS).
 Nutrient concentrations of filtered water samples were measured via
 spectrophotometry (total phosphorus) and by a Total Organic Carbon
 Analyzer with Total Nitrogen Unit (total nitrogen). Lipids were extracted
 from biomass filter samples, purified, derivatized (methylated or
 acetylated) and quantified by gas chromatography–flame ionization
 detection (GC-FID). Compound-specific
 δ<sup>2</sup>H<sub>lipid </sub>values of
 short-chain fatty acids, sterols and phytol were measured by GC-IRMS.
 δ<sup>2</sup>H<sub>lipid </sub>values were
 corrected for hydrogen added during derivatization and
 δ<sup>2</sup>H<sub>sterol</sub> values were
 further corrected for biases related to peak dimensions.
description: # Algal lipid distributions and hydrogen isotope ratios reflect
 phytoplankton community dynamics in Rotsee (Switzerland)
 [https://doi.org/10.5061/dryad.9s4mw6mrm
 ](https://doi.org/10.5061/dryad.9s4mw6mrm) ## Description of the data and
 file structure This dataset comprises different parameters measured
 biweekly in the water column of Rotsee during a one-year sampling period.
 Measurements occurred at 1 m depth (A) and the chlorophyll maximum depth
 at the respective sampling date (B). Sample names include the lake name
 (ROT), the date (yy-mm-dd), and the sampling depth (A or B). Different
 specifications were made for biovolume data, i.e., all phytoplankton
 including cyanobacteria, eukaryotic algae excluding cyanobacteria, and
 biovolume with and without microzooplankton contribution.  The following
 files contain (1) phytoplankton and microzooplankton biovolume (absolute
 values), (2) nutrient concentrations and temperature, (3) concentrations
 of different algal lipids (fatty acids, sterols and phytol), hydrogen
 isotope ratios of (4) algal lipids, and (5) lake water, expressed as d2H
 values, (6) the relative offset between d2H values of different lipids,
 expressed as epsilon values (ε2Lipid1/Lipid2 = (d2H
 Lipid1+1)/(d2HLipid2+1) – 1)), (7) the relative contribution of individual
 algal and microzooplankton groups to total eukaryotic biovolume, (8) the
 relative contribution of individual algal groups to eukaryotic algal
 biovolume, (9) the relative contribution of individual algal and
 microzooplankton groups to total biovolume, (10) the relative contribution
 of individual algal groups to phytoplankton biovolume, and (11) the
 relative contribution of single species to the biovolume of the
 phytoplankton and microzooplankton group they belong to. ### Files and
 variables #### **File: phyto\_microzooplankton\_biovolume\_ROT19.csv**
 **Variables** * cyanobacteria_um3L: summed biovolume of algal species
 belonging to the genus *Cyanophyceae* in µm^3/L * green.algae_um3L: summed
 biovolume of algal species belonging to the genus *Chloro-* and
 *Zygnemophyceae* in µm^3/L * Chrysophyta_um3L: summed biovolume of algal
 species belonging to the genus *Chrysophyceae* in µm^3/L *
 Diatoms_um3L: summed biovolume of algal species belonging to the genus
 *Bacillariophyceae* in µm^3/L * Dinoflagellates_um3L: summed biovolume of
 photosynthetic algal species belonging to the genus *Dinophyceae* in
 µm^3/L * Cryptophyceae_um3L: summed biovolume of algal species belonging
 to the genus *Cryptophyceae* in µm^3/L * Ciliata_um3L: summed biovolume of
 Ciliata species in µm^3/L * Rotifera_um3L: summed biovolume of Rotifera
 species in µm^3/L * Gymnodinium_helveticum_um3L: biovolume of *Gymnodinium
 helveticum* (a phagocytotic, non-photosynthetic dinoflagellate species) in
 µm^3/L **File: TN_TP_Temp_ROT19.csv** **Variables** * Total_Nitrogen_mgL:
 summed concentrations of nitrate, ammonia and nitrite in mg/L *
 Total_Phosphor_ugL: summed concentrations of phosphate and dissolved
 phosphorus in µg/L * Temp_C: temperature in Celsius **File:
 Lipid_conc_watercolumn_ROT19.csv** **Variables** * C14:0_ugL:
 concentration of C14:0 fatty acid (myristic acid) in µg/L *
 C16:1_ugL: concentration of C16:1 fatty acid (palmitoleic acid) in µg/L *
 C16:0_ugL: concentration of C16:0 fatty acid (palmitic acid) in µg/L *
 C18:3nx_ugL: summed concentrations of C18:3n3 (linolenic acid) co-eluting
 with C18:3n6 (γ-linolenic) fatty acid in µg/L * C18:2_ugL: concentration
 of C18:2  fatty acid (linoleic acid) in µg/L * C18:x_ugL: summed
 concentrations of C18:1n9c (oleic acid) co-eluting with C18:2n6t
 (linolelacidic acid) fatty acid in µg/L * C18:1_ugL: concentration of
 C18:1 fatty acid (elaidic acid) in µg/L * C18:0_ugL: concentration of
 C18:0 fatty acid (stearic acid) in µg/L * C20:3nx_ugL: summed
 concentrations of C20:3n3 (cis-11,14,17-eicosatrienoic acid) co-eluting
 with C20:3n6 (cis-8,11,14-eicosatrienoic acid) fatty acid in µg/L *
 C20:4_ugL: concentration of C20:4 fatty acid (arachidonic acid) in µg/L *
 C22:6_ugL: concentration of C22:6 fatty acid (docosahexaenoic acid) in
 µg/L * C22:2_ugL: concentration of C22:2 fatty acid (docosadienoic acid)
 in µg/L * brassicasterol_ugL: concentration of brassicasterol
 (24-methylcholesta-5,22-dien-3β-ol) in µg/L *
 cholesterol_ugL: concentration of cholesterol (cholest-5-en-3β-ol) in µg/L
 * diplopterol_ugL: concentration of diplopterol (hopan-22-ol) in µg/L *
 ergosterol_ugL: concentration of ergosterol
 (methylcholesta-5,7,22-trien-3β-ol) in µg/L *
 sitosterol_ugL: concentration of sitosterol (24-ethylcholest-5-en-3β-ol)
 in µg/L * stigmasterol_ugL: concentration of stigmasterol
 (24-ethylcholesta-5,22-dien-3β-ol) in µg/L * phytol_ugL: concentration of
 phytol (((2E,7R,11R)-3,7,11,15-Tetramethyl-2-hexadecen-1-ol) in µg/L
 **File: d2H_lipids_ROT19.csv** **Variables** * C16.0_Avg.d2H_VSMOW: d2H
 value of C16:0 fatty acid (palmitic acid), expressed in permil relative to
 Vienna Standard Mean Ocean Water (VSMOW)  *
 brassicasterol_Avg.d2H_VSMOW: d2H value of brassicasterol
 (24-methylcholesta-5,22-dien-3β-ol), expressed in permil relative to
 Vienna Standard Mean Ocean Water (VSMOW)  * ergosterol_Avg.d2H_VSMOW: d2H
 value of ergosterol (methylcholesta-5,7,22-trien-3β-ol), expressed in
 permil relative to Vienna Standard Mean Ocean Water (VSMOW)  *
 sitosterol_Avg.d2H_VSMOW: d2H value of sitosterol
 (24-ethylcholest-5-en-3β-ol), expressed in permil relative to Vienna
 Standard Mean Ocean Water (VSMOW) * stigmasterol_Avg.d2H_VSMOW: d2H value
 of stigmasterol (24-ethylcholesta-5,22-dien-3β-ol), expressed in permil
 relative to Vienna Standard Mean Ocean Water (VSMOW)  *
 phytol_Avg.d2H_VSMOW: d2H value of phytol
 (((2E,7R,11R)-3,7,11,15-Tetramethyl-2-hexadecen-1-ol), expressed in permil
 relative to Vienna Standard Mean Ocean Water (VSMOW)  **File:
 d2H_H2O_ROT19.csv** **Variables** * H2O_Avg.d2H_VSMOW : d2H value of lake
 water (H2O), expressed in permil relative to Vienna Standard Mean Ocean
 Water (VSMOW) 'Avg' in d2H variable names refers to
 'average' as the mean d2H value of replicate measurements.
 Standard deviations of d2H measurements (SD) are listed in the column
 directly following each variable. These values represent 1 standard
 deviation of replicate measurements. #### File:
 epsilon\_lipid1\_lipid2\_ROT19.csv ##### Variables * epsilon_C16.0_phytol:
 relative offset between d2H values of C16:0 fatty acid and phytol ((d2H
 C16:0+1)/(d2H phytol+1) – 1)),  expressed in permil *
 epsilon_C16.0_sterol: relative offset between d2H values of C16:0 fatty
 acid and sterols ((d2H C16:0+1)/(d2H sterol+1) – 1)),  expressed in permil
 * epsilon_sterol_phytol: relative offset between d2H values of sterols and
 phytol ((d2H sterols+1)/(d2H phytol+1) – 1)),  expressed in permil ####
 File: eukaryotic\_algae\_microzooplankton\_rel\_biovolume\_ROT19.csv #####
 Variables * green.algae_%: relative contribution of green algae to the
 summed biovolume of eukaryotes in percent * Chrysophyta_%: relative
 contribution of *Chrysophyceae* to the summed biovolume of eukaryotes in
 percent * Diatoms_%: relative contribution of *Bacillariophyceae*
 (diatoms) to the summed biovolume of eukaryotes in percent *
 Dinoflagellates_%: relative contribution of
 photosynthetic *Dinophyceae* (dinoflagellates) to the summed biovolume of
 eukaryotes in percent * Gymnodinium_helveticum_%: relative contribution of
 *Gymnodinium helveticum* (a phagocytotic, non-photosynthetic
 dinoflagellate species) to the summed biovolume of eukaryotes in percent *
 Cryptophyceae_%: relative contribution of *Cryptophyceae* to the summed
 biovolume of eukaryotes in percent * Ciliata_%: relative contribution of
 Ciliata to the summed biovolume of eukaryotes in percent *
 Rotifera_%: relative contribution of Rotifera to the summed biovolume of
 eukaryotes in percent #### File:
 eukaryotic\_algal\_rel\_biovolume\_ROT19.csv ##### Variables *
 green.algae_%: relative contribution of green algae to the summed
 biovolume of eukaryotic algae in percent * Chrysophyta_%: relative
 contribution of *Chrysophyceae* to the summed biovolume of eukaryotic
 algae in percent * Diatoms_%: relative contribution of *Bacillariophyceae*
 (diatoms) to the summed biovolume of eukaryotic algae in percent *
 Dinoflagellates_%: relative contribution of
 photosynthetic *Dinophyceae* (dinoflagellates) to the summed biovolume of
 eukaryotic algae in percent * Cryptophyceae_%: relative contribution of
 *Cryptophyceae* to the summed biovolume of eukaryotic algae in percent
 #### File: phyto\_microzooplankton\_rel\_biovolume\_ROT19.csv #####
 Variables * cyanobacteria_%: relative contribution of
 *Cyanophyceae* (cyanobacteria) to the summed biovolume of phyto-/ and
 microzooplankton in percent * green.algae_%: relative contribution of
 green algae to the summed biovolume of phyto-/ and microzooplankton in
 percent * Chrysophyta_%: relative contribution of *Chrysophyceae* to the
 summed biovolume of phyto-/ and microzooplankton in percent *
 Diatoms_%: relative contribution of *Bacillariophyceae* (diatoms) to the
 summed biovolume of phyto-/ and microzooplankton in percent *
 Dinoflagellates_%: relative contribution of
 photosynthetic *Dinophyceae* (dinoflagellates) to the summed biovolume of
 phyto-/ and microzooplankton in percent *
 Gymnodinium_helveticum_%: relative contribution of *Gymnodinium
 helveticum* (a phagocytotic, non-photosynthetic dinoflagellate species) to
 the summed biovolume of phyto-/ and microzooplankton in percent *
 Cryptophyceae_%: relative contribution of *Cryptophyceae* to the summed
 biovolume of phyto-/ and microzooplankton in percent * Ciliata_%: relative
 contribution of Ciliata to the summed biovolume of phyto-/ and
 microzooplankton in percent * Rotifera_%: relative contribution of
 Rotifera to the summed biovolume of phyto-/ and microzooplankton in
 percent #### File: phytoplankton\_rel\_biovolume\_ROT19.csv #####
 Variables * cyanobacteria_%: relative contribution of
 *Cyanophyceae* (cyanobacteria) to the summed biovolume of phytoplankton in
 percent * green.algae_%: relative contribution of green algae to the
 summed biovolume of phytoplankton in percent * Chrysophyta_%: relative
 contribution of *Chrysophyceae* to the summed biovolume of phytoplankton
 in percent * Diatoms_%: relative contribution of *Bacillariophyceae*
 (diatoms) to the summed biovolume of phytoplankton in percent *
 Dinoflagellates_%: relative contribution of
 photosynthetic *Dinophyceae* (dinoflagellates) to the summed biovolume of
 phytoplankton in percent * Cryptophyceae_%: relative contribution of
 *Cryptophyceae* to the summed biovolume of phytoplankton in percent ####
 File: phyto\_microzooplankton\_species\_rel\_biovolume\_ROT19.csv
 **Description:** In this datafile, each variable is indicating the
 relative contribution of individual species to the phytoplankton or
 microzooplankton group they belong to, e.g., the relative contribution of
 *Asterionella formosa* to *Bacillariophyceae* (diatoms) in percent. If no
 species level could be determined, cells were summarized to the next
 taxonomic classification. **General:** Missing values in each file are
 indicated as '#NV'. ## Access information Other publicly
 accessible locations of some the data: *
 [https://github.com/antoniaKlatt/Klatt_etal_2024_phytoplankton_Rotsee](https://github.com/antoniaKlatt/Klatt_etal_2024_phytoplankton_Rotsee)