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Dryad

Data from: Taxon-specific hydrogen isotope signals in cultures and mesocosms facilitate ecosystem and hydroclimate reconstruction

Cite this dataset

Ladd, S. Nemiah et al. (2024). Data from: Taxon-specific hydrogen isotope signals in cultures and mesocosms facilitate ecosystem and hydroclimate reconstruction [Dataset]. Dryad. https://doi.org/10.5061/dryad.nvx0k6f0v

Abstract

Phytoplankton play a key role in biogeochemical cycles, impacting atmospheric and aquatic chemistry, food webs, and water quality. However, it remains challenging to reconstruct changes in algal community composition throughout the geologic past, as existing proxies are suitable only for a subset of taxa and/or influenced by degradation. Here, we investigate if compound-specific hydrogen isotope ratios (δ2H values) of common algal lipids can serve as (paleo)ecological indicators. First, we grew 20 species of algae – representing cyanobacteria, diatoms, dinoflagellates, green algae, and cryptomonads – in batch cultures under identical conditions and measured δ2H values of their lipids. Despite identical source water δ2H values, lipid δ2H values ranged from -455 ‰ to -52 ‰, and clustered according to taxonomic groups and chemical compound classes. In particular, green algae synthesized fatty acids with higher δ2H values than other taxa, cyanobacteria synthesized phytol with relatively low δ2H values, and diatoms synthesized sterols with higher δ2H values than other eukaryotes. Second, we assessed how changes in algal community composition can affect net δ2H values of common algal lipids in 20 experimental outdoor ponds, which were manipulated via nutrient loading, and the addition of macrophytes and mussels. High algal biomass in the ponds, which was mainly caused by cyanobacterial and green algal blooms, was associated with higher δ2H values for generic fatty acids, relatively stable δ2H values for phytol and the dinoflagellate biomarker dinostanol, and lower δ2H values for the more cosmopolitan sterol stigmasterol. These results are consistent with expectations from our culture-based analyses, suggesting that measuring δ2H values of multiple lipids from sediment and calculating 2H-offsets between them can resolve changes in algal community composition from changes in source water isotopes. With an appropriate availability of sedimentary lipids, this approach could permit the reconstruction of both taxonomic variability and hydroclimate from diverse sedimentary systems.

README: Data from: Taxon-specific hydrogen isotope signals in cultures and mesocosms facilitate ecosystem and hydroclimate reconstruction

https://doi.org/10.5061/dryad.nvx0k6f0v

This data set contains hydrogen isotope ratios, expressed as d2H values, of algal lipids from two experiments: (1) batch cultures of different algal species under identical laboratory conditions and (2) large-volume mesocosms.

Description of the data and file structure

File list: 

  1. Algal_Culture_d2H.csv (results from batch cultures)
  2. Pond_d2H.csv (results from large volume mesocosms)

Variable list:

  • Species: Genus and species of cultured algae
  • Group: Algal taxonomic group used for classifying and plotting data
  • Class: Taxonomic class
  • Number Replicate Cultures: Total number of replicate batch cultures
  • d2H C16:0 FA: d2H value of C16:0 fatty acid (hexadecanoic acid; palmitic acid), expressed in per mil relative to Vienna Standard Mean Ocean Water (VSMOW).
  • d2H Phytol: d2H value of Phytol, expressed per mil relative to VSMOW.
  • d2H Sterol 1: d2H value of the first sterol that eluted on the GC-IRMS, if present, expressed in per mil relative to VSMOW. The specific compound differs among eukaryotic algae. Cyanobacteria did not produce any sterols.
  • d2H Sterol 2: d2H value of the second sterol that eluted on the GC-IRMS, if present, expressed in per mil relative to VSMOW. The specific compound differs among eukaryotic algae. Cyanobacteria did not produce any sterols.
  • d2H Sterol 3: d2H value of the third sterol that eluted on the GC-IRMS, if present, expressed in per mil relative to VSMOW. The specific compound differs among eukaryotic algae. Cyanobacteria did not produce any sterols.
  • d2H Sterol 4: d2H value of the fourth sterol that eluted on the GC-IRMS, if present, expressed in per mil relative to VSMOW. The specific compound differs among eukaryotic algae. Cyanobacteria did not produce any sterols.
  • d2H Sterol 5: d2H value of the fifth sterol that eluted on the GC-IRMS, if present, expressed in per mil relative to VSMOW. The specific compound differs among eukaryotic algae. Cyanobacteria did not produce any sterols.
  • Pond: Unique ID of the experimental pond used in the mesocosm experiment
  • Treatment: Mesocosm treatment. Ponds had either Mussels, Macrophytes, or Both, Neither with nutrient additions (Nutrient controls), or Neither without nutrient additions (oligotrophic controls)
  • Sampling date: Date when samples were collected, in YYMMDD format
  • Water d2H: d2H value of filtered pond water, expressed in per mil relative to VSMOW
  • d2H C14:0 FA: d2H value of C14:0 fatty acid (tetradecanoic acid, myristic acid), expressed in per mil relative to VSMOW.
  • d2H C16:1 FA: d2H value of C16:1 fatty acid ((9Z)-hexadecenoic acid, palmitoleic acid), expressed in per mil relative to VSMOW.
  • d2H C18:0 FA: d2H value of C18:0 fatty acid (octadecanoic acid, stearic acid), expressed in per mil relative to VSMOW.
  • d2H C18:x FA: d2H value of chromatographically unresolved unsaturated C18 fatty acids (cis-9-octadecanoic acid, trans-9-octadecanoic acid, and linolelaidic acid), expressed in per mil relative to VSMOW
  • d2H C18:2 FA: d2H value of C18:2 fatty acid (linoleic acid, cis-9,12-octadecanoic acid), expressed in per mil relative to VSMOW.
  • d2H C20:4n6 FA: d2H value of C20:4n6 fatty acid (arachidonic acid, (5*Z*,8*Z*,11*Z*,14*Z*)-Icosa-5,8,11,14-tetraenoic acid), expressed in per mil relative to VSMOW.
  • d2H C20:5 FA: d2H value of C20:5n3 fatty acid (eicosapentaenoic acid; (5*Z*,8*Z*,11*Z*,14*Z*,17*Z*)-Icosa-5,8,11,14,17-pentaenoic acid), expressed in per mil relative to VSMOW.
  • d2H C22:6 FA: d2H value of C22:6n3 fatty acid (docosahexaenoic acid; (4*Z*,7*Z*,10*Z*,13*Z*,16*Z*,19*Z*)-Docosa-4,7,10,13,16,19-hexaenoic acid, expressed in per mil relative to VSMOW.
  • d2H Campesterol: d2H value of campesterol (Campest-5-en-3β-ol), expressed in per mil relative to VSMOW.
  • d2H Dinostanol: d2H value of dinostanol (4a,23,24-trimethyl-5a-cholestan-3b-ol), expressed in per mil relative to VSMOW.
  • d2H Brassicasterol: d2H value of brassicasterol (Ergosta-5,22-dien-3β-ol), expressed in per mil relative to VSMOW.
  • d2H Cholesterol: d2H value of cholesterol (Cholest-5-en-3β-ol), expressed in per mil relative to VSMOW.
  • d2H Stigmasterol: d2H value of stigmasterol (Stigmasta-5,22-dien-3β-ol), expressed in per mil relative to VSMOW.

Standard deviations are reported in the column directly following each variable and denoted as st dev variable name. These values represent 1 standard deviation of replicate measurements, or the long-term precision of the quality control standard, whichever value was larger.

Values for which no data were obtained are left blank.

Methods

20 species of phytoplankton were cultured under identical conditions in batch cultures. Biomass was filtered from cultured water. Mesocosm experiments were conducted in large-volume experimental ponds. Algal biomass was filtered from the water at three time points from each of the 20 experimental ponds. From both sample sets, lipids were extracted and purified, derivatized (methylated or acetylated) and compound-specific hydrogen isotope ratios of fatty acids, phytol, and sterols were measured by gas chromatography - isotope ratio mass spectrometry (GC-IRMS). Resulted lipid δ2H values are corrected for hydrogen added during derivatization. The isotopic composition of filtered water was determined by cavity ring-down spectroscopy.

Funding

National Science Foundation, Award: EAR-1452254, Earth Sciences Postdoctoral Fellowship

Swiss National Science Foundation, Award: PCEFP2_194211, Eccellenza

Swiss Federal Institute of Aquatic Science and Technology, Internal funds