Preprints
https://doi.org/10.5194/bg-2024-1
https://doi.org/10.5194/bg-2024-1
05 Mar 2024
 | 05 Mar 2024
Status: this preprint is currently under review for the journal BG.

Variations of polyphenols and carbohydrates of Emiliania huxleyi grown under simulated ocean acidification conditions

Milagros Rico, Paula Santiago-Díaz, Guillermo Samperio-Ramos, Melchor González-Dávila, and Juana Magdalena Santana-Casiano

Abstract. Global environmental changes strongly affect the growth and biochemical composition of microalgae. Cultures of the coccolithophore Emiliania huxleyi were grown under four different CO2-controlled pH conditions (7.75, 7.90, 8.10, and 8.25) to improve understanding of the adaptive mechanisms of these organisms through changes in phenolic compounds and carbohydrate content and composition under ocean acidification (OA) scenarios. The highest algal biomass peaks, 1.07 (± 0.10) and 1.04 (± 0.06) × 108 cells L−1, were observed in the microcosms with intermediate CO2 levels (pH 8.10 and 7.90 respectively). Intra- and extracellular phenolic compounds were identified and quantified by Reverse Phase-High Performance Liquid Chromatography (RP-HPLC). The highest concentrations of total exuded phenolics were found in cultures with lower cell densities, at pH 8.25 (43±3 nM) and 7.75 (18.0±0.9 nM). Accumulation of intracellular phenolic compounds was observed in cells with decreasing pH, reaching the maximum level (9.24±0.19 attomole cell-1) at the lowest pH (7.75). The total carbohydrate content inside the cells increased with decreasing pH from 8.25 to 8.10, remaining constant at pH 7.90, and decreasing at lower pH. The presence of antioxidants was determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical inhibition and ferric-reducing antioxidant power (FRAP) assays. The highest activity in both tests was exhibited by cells grown at pH 7.75.

Milagros Rico, Paula Santiago-Díaz, Guillermo Samperio-Ramos, Melchor González-Dávila, and Juana Magdalena Santana-Casiano

Status: open (until 23 May 2024)

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  • RC1: 'Comment on bg-2024-1', Anonymous Referee #1, 30 Mar 2024 reply
Milagros Rico, Paula Santiago-Díaz, Guillermo Samperio-Ramos, Melchor González-Dávila, and Juana Magdalena Santana-Casiano
Milagros Rico, Paula Santiago-Díaz, Guillermo Samperio-Ramos, Melchor González-Dávila, and Juana Magdalena Santana-Casiano

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Short summary
Organic matter exuded by microorganisms under ocean acidification conditions (OA) forms complexes that increase the residence time of the reduced form of trace metals such as iron, an essential micronutrient. Global environmental change influences the metabolic functions and composition of microalgae, with implications for higher trophic levels and biodiversity loss. The composition of cells and exudates under OA is of crucial interest for understanding the consequences of future scenarios.
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