Fatty acid isotopic fractionation in the diatom Chaetoceros muelleri

Type Article
Date 2021-04
Language English
Author(s) Remize Marine1, 2, Planchon Frederic1, Loh Ai Ning2, Le Grand Fabienne5, Mathieu-Resuge Margaux1, 3, Bideau Antoine1, Corvaisier Rudolph5, Volety Aswani4, Soudant Philippe5
Affiliation(s) 1 : Univ Brest, CNRS, IRD, Ifremer, UMR 6539 LEMAR, F-29280 Plouzané, France
2 : University of North Carolina Wilmington, Department of Earth and Ocean Sciences, Center for Marine Science, 5600 Marvin K. Moss Ln, Wilmington, NC 28403, USA
3 : WasserCluster Lunz – Inter-University Centre for Aquatic Ecosystem Research, Dr. Carl Kupelwieser Promenade 5, A-3293 Lunz am See, Austria
4 : Elon University, 50 Campus Drive, Elon, NC 27244, USA
5 : Univ Brest, CNRS, IRD, Ifremer, UMR 6539 LEMAR, F-29280 Plouzané, France
Source Algal Research-biomass Biofuels And Bioproducts (2211-9264) (Elsevier BV), 2021-04 , Vol. 54 , P. 102164 (14p.)
DOI 10.1016/j.algal.2020.102164
Keyword(s) Fractionation, Stable isotopes, Photosynthesis, Phytoplankton, Chaetoceros muelleri, Fatty acid synthesis

Carbon isotopic fractionation was studied during the development of the diatom Chaetoceros muelleri grown in batch culture with 13C-depleted CO2 addition. Cellular and growth parameters and isotopic composition of dissolved inorganic carbon and particulate organic carbon were monitored every two days, while the content and isotopic composition of individual fatty acid in polar lipid and neutral lipid were measured on the 5th day (end of exponential phase), 10th and 14th days (stationary phase). Continuous addition of petrochemical CO2 to the algae led to a rapid and strong modification of dissolved inorganic carbon isotopic composition with cascading effects on particulate organic carbon and fatty acid isotopic compositions. Carbon isotope fractionation in Chaetoceros muelleri ranged from 17‰ to 25‰ and changed according to culture ages. Isotopic fractionation into fatty acids, overall, was similar between polar and neutral lipids, and was systematically higher than in particulate organic carbon. At the end of the exponential growth phase, the isotopic composition of individual fatty acids varied from −51.3‰ to −58.4‰. At this culture age, large differences in the isotopic compositions between fatty acids were observed. Polyunsaturated fatty acids such as 16:3n-4, 18:4n-3, and 20:5n-3 were more strongly 13C-depleted than other fatty acids such as 14:0, 16:0, 16:1n-7 or 18:1n-9. These results showed how isotopic effects occur during the desaturation and elongation phases. Such isotopic effects were also supported by the lower δ13C of averaged δ13C of saturated fatty acids and monounsaturated fatty acids as compared to those of polyunsaturated fatty acids. However, during the stationary phase, fatty acid isotopic compositions were less variable and closer to particulate organic carbon, while saturated and monounsaturated fatty acids were more depleted than polyunsaturated fatty acids. Our study underlined the importance of consideration of phytoplankton physiological status when conducting ecological and biogeochemical studies as they appeared to strongly control phytoplankton carbon isotopic composition.

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Remize Marine, Planchon Frederic, Loh Ai Ning, Le Grand Fabienne, Mathieu-Resuge Margaux, Bideau Antoine, Corvaisier Rudolph, Volety Aswani, Soudant Philippe (2021). Fatty acid isotopic fractionation in the diatom Chaetoceros muelleri. Algal Research-biomass Biofuels And Bioproducts, 54, 102164 (14p.). Publisher's official version : https://doi.org/10.1016/j.algal.2020.102164 , Open Access version : https://archimer.ifremer.fr/doc/00684/79570/