Abstract:
A seasonal cycle of the FA composition of particulate organic matter from surface waters, Chlorophyll-a maximum layer and bottom sea ice, sampled during the MOSAiC expedition in the Central Arctic Ocean (2019-2020), suggests the importance of phylogenetic and environmental drivers. To improve our understanding of these different drivers, we conducted culture experiments with 32 cold-water algal strains where temperature, light intensity, and nutrient supply were manipulated individually or in combination. The culture experiments were carried out at the Culture Collection of Algae and Protozoa (CCAP; Oban, Scotland), the Roscoff Culture Collection (RCC; Roscoff, France) and the Alfred-Wegener-Institute-Helmholtz-Centre for Polar and Marine Research (AWI; Bremerhaven, Germany). The strains were part of the culture collections, had been isolated in the Arctic (25 strains), Southern Ocean (2 strains) or North Atlantic (5 strains), and included diatoms, chlorophytes, haptophytes, cryptophytes, chrysophytes, dinoflagellates and cyanobacteria. Some of the species are Arctic sea ice diatoms (e.g. Nitzschia frigida, Attheya spp.) or pelagic diatoms (e.g. Thalassiosira gravida), while others are non-diatom species that are becoming increasingly prominent in the Arctic, e.g. the coccolithophore Emiliania huxleyi (synonym Gephyrocapsa huxleyi), the prymnesiophyte Phaeocystis pouchetii, the chlorophyte Micromonas spp. and the cyanobacterium Synechococcus spp.. The experiments can be divided into three groups: First, those that tested a low light-low temperature setting, second, those that tested a low light-low temperature and a higher light-higher temperature setting and, third, those that tested the effect of nutrient (nitrate, phosphate and silicate) shortage in combination with low and high light intensity. The first set of experiments was conducted with all 32 strains, the second set with all strains grown at CCAP and AWI, and the third set focuses on the keystone under-ice diatom Melosira arctica. The experiments were run for 4-7 weeks to accumulate sufficient biomass for biomarker extractions (FA and sterols), C:N analysis and light-microscopy of cell size and cell concentration. At the end of the experiments, the algae were filtered onto GF/F filters and deep frozen until analysis. This dataset comprises the results from the FA analysis only (sterol and C:N analysis are separate). The separation of the lipid biomarkers was carried out at the University of Plymouth. After addition of internal standards for FA and sterols, the filters were saponified with KOH. Thereafter, non-saponifiable lipids (sterols) were extracted with hexane and purified by open column chromatography on silica gel. FA were obtained by adding concentrated HCl to the saponified solution and re-extracted with hexane. Further steps of the FA analysis were carried out at the AWI. Here samples were converted into fatty acid methyl esters (FAME) and analysed using an Agilent 6890N gas chromatograph with FID detector. The Clarity chromatography software system (DataApex, Czech Republic) was used for chromatogram data evaluation. FAME were quantified via the internal standard, Tricosanoic acid methyl ester (23:0) (Supelco, Germany) to provide the total amount of FA (TFA) per filter. These FA datasets of cultured algae are presented in a manuscript together with the FA pattern seen in sea ice- and water column POM in the CAO during the MOSAiC expedition and in previously published data from Arctic shelf regions. The manuscript focusses mainly on two important long-chain omega-3 FA (eicosapentaenoic acid and docosahexaenoic acid) that are considered essential for the nutrition of higher trophic levels, including humans, and their production to decline with global temperature rise.
Contributions by KS were funded by the UK's Natural Environment Research Council MOSAiC Thematic project SYM-PEL: 'Quantifying the contribution of sympagic versus pelagic diatoms to Arctic food webs and biogeochemical fluxes: application of source-specific highly branched isoprenoid biomarkers'/ (NE/S002502/1). CRM was funded by the NERC National Capability Services and Facilities Programme (NE/R017050/1).
Keywords:
Arctic, DHA, EPA, MOSAiC, Melosira arctica, cultured algae, fatty acids, light intensity, lipid biomarker, nutrients, sea ice, temperature
Schmidt, K., Graeve, M., Hoppe, C., Rokitta, S., Welteke, N., Menendez, C., Probert, I., Brenneis, T., Belt, S., & Atkinson, A. (2023). Fatty acid composition of 32 cold-water algal strains cultured under different conditions to support the interpretation of in situ algal FA data from the MOSAiC expedition 2019/2020 (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/bb4b1e74-d5af-4a73-9174-62a01807c641
| Access Constraints: | No restrictions apply. |
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| Use Constraints: | Data released under Open Government Licence V3.0: http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/. |
| Creation Date: | 2023-12-14 |
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| Dataset Progress: | Complete |
| Dataset Language: | English |
| ISO Topic Categories: |
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| Parameters: |
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| Personnel: | |
| Name | UK Polar Data Centre |
| Role(s) | Metadata Author |
| Organisation | British Antarctic Survey |
| Name | Katrin Schmidt |
| Role(s) | Investigator |
| Organisation | University of Plymouth |
| Name | Martin Graeve |
| Role(s) | Investigator |
| Organisation | Alfred Wegener Institute |
| Name | Clara J M Hoppe |
| Role(s) | Investigator |
| Organisation | Alfred Wegener Institute |
| Name | Sebastian Rokitta |
| Role(s) | Investigator |
| Organisation | Alfred Wegener Institute |
| Name | Nahid Welteke |
| Role(s) | Investigator |
| Organisation | Alfred Wegener Institute |
| Name | Cecilia R Menendez |
| Role(s) | Investigator |
| Organisation | Scottish Association for Marine Science |
| Name | Ian Probert |
| Role(s) | Investigator |
| Organisation | Sorbonne University |
| Name | Tina Brenneis |
| Role(s) | Investigator |
| Organisation | Alfred Wegener Institute |
| Name | Prof Simon T Belt |
| Role(s) | Investigator |
| Organisation | University of Plymouth |
| Name | Angus Atkinson |
| Role(s) | Investigator |
| Organisation | Plymouth Marine Laboratory |
| Parent Dataset: | N/A |
| Reference: | Associated article: Schmidt, K., Graeve, M., Hoppe, C. J., Torres-Valdes, S., Welteke, N., Whitmore, L. M., ... & Zhuang, Y. (2024). Essential omega-3 fatty acids are depleted in sea ice and pelagic algae of the Central Arctic Ocean. Global Change Biology, 30(1), e17090. References: Fernandez-Mendez, M., Wenzhofer, F., Peeken, I., Sorensen, H. L., Glud, R. N., & Boetius, A. (2014). Composition, buoyancy regulation and fate of ice algal aggregates in the Central Arctic Ocean. PLoS One, 9(9), e107452. Guillard, R.R.L. and Ryther, J.H. 1962. Studies of marine planktonic diatoms. I. Cyclotella nana Hustedt and Detonula confervacea Cleve. Can. J. Microbiol. 8: 229-239. Leblond, J. D., Anderson, B., Kofink, D., Logares, R., Rengefors, K., & Kremp, A. (2006). Fatty acid and sterol composition of two evolutionarily closely related dinoflagellate morphospecies from cold Scandinavian brackish and freshwaters. European Journal of Phycology, 41(3), 303-311. Spilling, K., and Markager, S. (2008). Ecophysiological growth characteristics and modeling of the onset of the spring bloom in the Baltic Sea. Journal of Marine Systems, 73(3-4), 323-337. |
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| Quality: | The fatty acid profiles were compared to several commercial- and self-produced standards (e.g. Arctic algae standard, Bacteria standard, Calanus spp. standard), and fatty acid peaks were identified accordingly. In a few cases, samples were also analysed with the mass spectrometer and peaks were identified via (1) the mass of the compound, (2) the retention time of the compound and (3) the equivalent chain length method. Unusual peaks were also compared with published FA profiles from related species (e.g. Leblond et al. 2006 for cold-adapted dinoflagellates). | |
| Lineage: | Microalgae cultures: In 2022, we conducted FA analysis on 32 cold-water strains that were isolated in the Arctic (25 strains), Southern Ocean (2 strains) or North Atlantic (5 strains), and included diatoms, chlorophytes, haptophytes, cryptophytes, chrysophytes, dinoflagellates and cyanobacteria. These strains were either obtained from commercial culture collections (CCAP or RCC) or provided by the AWI. The CCAP cultures were inoculated in 50 ml Erlenmeyer conical flasks with 25 ml of F/2 medium and added 60 micromol L-1 silicate for diatoms (Guillard and Ryther 1962). The algal strains were grown for four weeks at either low temperature - low light intensity (3-4 degrees Celsius, 10 micromol m-2 s-1) or higher temperature - higher light intensity (8 degrees Celsius, 20 micromol m-2 s-1) and a light:dark cycle of 12:12 hrs. The culturing conditions at RCC resembled those at CCAP, but only for the low temperature - low light intensity (3-4d degrees Celsius, 10 micromol m-2 s-1). The algae growth rates were not monitored, but with these culture conditions and time span, the strains usually reach late exponential-early stationary growth (C. Rad-Menendez, I. Probert, pers. comm.). From each strain, two 5 ml technical replicates were filtered via a vacuum pump (-20 kPA) onto pre-combusted (12 h, 450 degrees Celsius) 25 mm Whatman GF/F filters, freeze dried and stored in aluminium foil at -20 degrees Celsius until FA analysis. Note: Three of the strains from CCAP (CCAP-1023/3, CCAP-1029/29, CCAP-1029/30) were obtained and analysed as 'Fragilariopsis sp.' but subsequently identified as 'Grammonema sp.'. Experiments with Melosira arctica: The experiments with Melosira arctica were carried out at the AWI in 2021 and 2022, using a strain that was isolated in the Central Arctic Ocean in 2015 (79.56 degrees N, 4.84 degrees W; strain PS93.1_030). The strain was grown as semi-continuous batch cultures under 6 different environmental conditions including the species' natural range of temperature, light and nutrient availability (Spilling and Markager 2008, Fernandez-Mendez et al. 2014). Therefore, low temperatures (0-1 dgrees Celsius) were combined with high and low light intensity (10 and 100 micromol m-2 s-2), each with high and low nutrient supply (details below), and higher temperatures (3 and 6 degrees Celsius) with high light and nutrient availability. Experiments were performed with 4 biological replicates in sterile 1-L Schott bottles in temperature-controlled rooms, with bottles at 3 and 6 degrees Celsius being immersed in water-filled aquaria for additional temperature stability. Day light lamps (Biolux T8, 6500K, Osram) provided continuous light and irradiance levels were adjusted with a black mesh fabric and measured using a 4 pi spherical sensor (Li-Cor) and data logger (ULM-500, Walz). Cells were cultivated in 0.2 micrometerm sterile-filtered Arctic seawater (salinity 33.5), with or without added macronutrients, vitamins and trace metals according to F/2 or F/20 media (Guillard and Ryther, 1962). Initial nutrient concentrations in set-ups with F/20 media were 10.4 +/-0.24 micromol L-1 nitrate-and-nitrite, 18.1 +/-1.36 micromol L-1 silicate and 1.2 +/- 0.19 micromol L-1 phosphate. In set-ups without added medium, initial nutrient concentrations were 1.8+/-0.07 micromol L-1 nitrate-and-nitrite, 14.4 +/-2.3 micromol L-1 silicate and 0.4 +/-0.01 micromol L-1 phosphate. To minimize changes in carbonate chemistry and to remain close to natural population densities, cultures were diluted every 1-2 weeks with Arctic seawater, with or without medium. Sufficient algal biomass for subsequent lipid analysis was grown after 4 weeks for cultures that received media, and after 7 weeks for those without media. At the end of the experiment, 2 technical replicates were taken from each biological replicate, filtered onto pre-combusted (12 h, 450 degrees Celsius) 25 mm Whatman GF/F filters, freeze dried and stored in aluminium foil at -20 degrees Celsius until FA analysis. All dilutions and final sampling were conducted under sterile conditions, using a laminar flow hood. Fatty acid analysis: The separation of the lipid biomarkers was carried out at the University of Plymouth. After addition of internal standards for FA and sterols, the filters were saponified with KOH. Thereafter, non-saponifiable lipids (sterols) were extracted with hexane and purified by open column chromatography on silica gel. FA were obtained by adding concentrated HCl to the saponified solution and re-extracted with hexane. Further steps of the FA analysis were carried out at the AWI. Here samples were converted into fatty acid methyl esters (FAME) and analysed using an Agilent 6890N gas chromatograph with FID detector. The Clarity chromatography software system (DataApex, Czech Republic) was used for chromatogram data evaluation. FAME were quantified via the internal standard, Tricosanoic acid methyl ester (23:0) (Supelco, Germany) to provide the total amount of FA (TFA) per filter. These TFA quantities per filter can be normalised to the volume of filtered seawater. Additionally, we provide the mass percentage composition of the TFA, considering 48 individual FA. Data details: TFA quantities per filter can be normalised to the volume of filtered seawater. Additionally, we provide the mass percentage composition of the TFA, considering 48 individual FA. The FA are presented in shorthand notation, i.e., A:B(n-x), where: A indicates the number of carbon atoms in the straight fatty acid chain, B represents the number of double bonds present, n represents the terminal methyl group and x denotes the position of the first double bond from the terminal end. The nomenclature of the fatty acids following IUPAC rules is provided. |
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| Temporal Coverage: | |
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| Start Date | 2021-07-04 |
| End Date | 2022-05-05 |
| Location: | |
| Location | N/A |
| Detailed Location | Isolated from the Arctic, Southern Ocean and North Atlantic, |
| Location | N/A |
| Detailed Location | Laboratory facilities of the culture collection sites (CCAP, RCC or AWI) |
| Data Collection: | Fatty acid analysis: FAME were quantified using an Agilent 6890N gas chromatograph (Agilent Technologies, USA) with a DB-FFAP capillary column (60 m, 0.25 mm I.D., 0.25 micrometer film thickness, Agilent Technologies, USA) supplied with a splitless injector and a flame ionization detector using temperature programming. Chromatogram data evaluation: Clarity chromatography software system (version 8.8.0, DataApex, Czech Republic) |
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| Data Storage: | There are 2 files: - 1 Fatty_acids_culture_MOSAiC.csv (28 KB) - READ_ME.txt (10 KB) Explanation of column headings: Species: lowest taxonomic category Culture_Collection: site that cultures the strain and did conduct the experiment Strain: name of culture collection and strain ID Class: higher taxonomic category Order: lower taxonomic category Isolation_site: Location where the strain was isolated Length_of_experiment_weeks: Number of weeks the experiment was conducted Temperature: temperature during the experiment Light_intensity: light intensity during the experiment Medium_type: specific mixture of nutrients and vitamins added to the culture flasks Medium_top-up: further addition of medium during the experiment (Yes/No) Replicate: Letter gives biological replicate, number gives technical replicate Final_cell_concentration_cells_per microliter: cell concentration at the end of the experiment Volume_filtered_milliliter: well-mixed subsample of the final culture used for FA analysis Total_fatty_acids_microgramme: total amount of FA on filter 12:0_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 14:0_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA Phytol_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 14:1n5_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA i-15:0_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA ai_15:0_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 15:0_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 15:1n5_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 16:0_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 16:1n9_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 16:1n7_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 16:1n5_percentage_of_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA i-17:0_percentage_of_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 16:2n4_percentage_of_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 17:0_percentage_of_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 16:3n4_percentage_of_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 16:4n3_percentage_of_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 16:4n1_percentage_of_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 18:0_percentage_of_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 18:1n9 _percentage of total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 18:1n7_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 18:1n5_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 18:2n6 _percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 18:3n6 _percentagetotal_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 18:3n3_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 18:4n3_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 18:5n3_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 18:5(n-X),20:0_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 20:1n11_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 20:1n9_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 20:1n7_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 20:1n5_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 20:2n6_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 20:3n6_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 20:4n6_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 20:3n3_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 20:4n3_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 20:5n3_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 22:0_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 22:1n11_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 22:1n9_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 22:1n7_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 22:2n6_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 22:4n6_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 22:4n3_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 22:5n3_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 24:0_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 24:1n11_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 24:1n9_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA 22:6n3_percentage_total_fatty_acids: Mass percentage of individual fatty acids. Proportion of individual FA as mass % of TFA Name, Short Name, Unit Dodecanoic acid, 12:0, % Tetradecanoic acid, 14:0, % (7R,11R)-3,7,11,15-tetramethylhexadec-2-en-1-ol, Phytol, % cis-9-Tetradecenoic acid, 14:1(n-5), % Isopentadecanoic acid, i-15:0, % Anteisopentadecanoic acid, a-15:0, % Pentadecanoic acid, 15:0, % cis-10-Pentadecenoic acid, 15:1(n-5), % Hexadecanoic acid, 16:0, % cis-7-Hexadecenoic acid, 16:1(n-9), % cis-9-Hexadecenoic acid, 16:1(n-7) ,% cis-11-Hexadecenoic acid, 16:1(n-5), % Isoheptadecanoic acid , i-17:0, % 9,12-Hexadecadienoic acid, 16:2(n-4), % Heptadecanoic acid, 17:0, % 6,9,12-Hexadecatrienoic acid, 16:3(n-4), % 4,7,10,13-Hexadecatetraenoic acid, 16:4(n-3), % 6,9,12,15-Hexadecatetraenoic acid, 16:4(n-1), % cis-9-Heptadecenoic acid, 17:1(n-8), % Octadecanoic acid, 18:0, % cis-9-Octadecenoic acid, 18:1(n-9), % cis-11-Octadecenoic acid, 18:1(n-7), % cis-13-Octadecenoic acid, 18:1(n-5), % all-cis-9,12-Octadecadienoic acid, 18:2(n-6), % all-cis-6,9,12-Octadecatrienoic, 18:3(n-6), % all-cis-9,12,15-Octadecatrienoic acid, 18:3(n-3), % all-cis-6,9,12,15-Octadecatetraenoic acid, 18:4(n-3), % Eicosanoic acid, 20:0, % cis-9-Eicosenoic acid, 20:1(n-11), % cis-11-Eicosenoic acid, 20:1(n-9), % cis-13-Eicosenoic acid, 20:1(n-7), % all-cis-11,14-Eicosasadienoic acid, 20:2(n-6), % all-cis-8,11,14-Eicosatrienoic acid, 20:3(n-6), % all-cis-5, 8,11,14-Eicosatetraenoic acid, 20:4(n-6), % all-cis-11,14,17-Eicosatrienoic acid, 20:3(n-3), % all-cis-8,11,14,17-Eicosatetraenoic acid, 20:4(n-3), % all-cis-5,8,11,14,17-Eicosapentaenoic acid, 20:5(n-3), % Docosanoic acid, 22:0, % cis-11-Docosenoate, 22:1(n-11), % cis-13-Docosenoic acid, 22:1(n-9), % cis-15-Docosenoic acid, 22:1(n-7), % cis-16,13-Docosadienoic acid, 22:2(n-6), % all-cis-7,10,13,16-Docosatetraenoic acid, 22:4(n-6), % all-cis-10,13,16,19-Docosatetraenoic acid, 24:4(n-3), % all-cis-7,10,13,16,19-Docosapentaenoic acid, 22:5(n-3), % Tetracosanoic acid, 24:0, % cis-13-Tetracosenoic acid, 24:1(n-11), % cis-15-Tetracosenoic acid, 24:1(n-9), % all-cis-4,7,10,13,16,19-Docosahexaenoic acid, 22:6(n-3), % |
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