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Variability in the organic ligands released by Emiliania huxleyi under simulated ocean acidification conditions

1 Institute of Oceanography and Global change, University of Las Palmas de Gran Canaria, Tafira Campus, 35017 Las Palmas, Spain
2 QOPNA, Department of Chemistry, University of Aveiro, Portugal

Special Issues: Marine and Coastal Ecosystems

The variability in the extracellular release of organic ligands by Emiliania huxleyi under four different pCO2 scenarios (225, 350, 600 and 900 μatm), was determined. Growth in the batch cultures was promoted by enriching them only with major nutrients and low iron concentrations. No chelating agents were added to control metal speciation. During the initial (IP), exponential (EP) and steady (SP) phases, extracellular release rates, normalized per cell and day, of dissolved organic carbon (DOCER), phenolic compounds (PhCER), dissolved combined carbohydrates (DCCHOER) and dissolved uronic acids (DUAER) in the exudates were determined.
The growth rate decreased in the highest CO2 treatment during the IP (<48 h), but later increased when the exposure was longer (more than 6 days). DOCER did not increase significantly with high pCO2. Although no relationship was observed between DCCHOER and the CO2 conditions, DCCHO was a substantial fraction of the freshly released organic material, accounting for 18% to 37%, in EP, and 14% to 23%, in SP, of the DOC produced. Growth of E. huxleyi induced a strong response in the PhCER and DUAER. While in EP, PhCER were no detected, the DUAER remained almost constant for all CO2 treatments. Increases in the extracellular release of these organic ligands during SP were most pronounced under high pCO2 conditions. Our results imply that, during the final growth stage of E. huxleyi, elevated CO2 conditions will increase its excretion of acid polysaccharides and phenolic compounds, which may affect the biogeochemical behavior of metals in seawater.
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Keywords Emiliania huxleyi; acidification; extracellular release; phenolic compounds dissolved uronic acids

Citation: Guillermo Samperio-Ramos, J. Magdalena Santana-Casiano, Melchor González-Dávila, Sonia Ferreira, Manuel A. Coimbra. Variability in the organic ligands released by Emiliania huxleyi under simulated ocean acidification conditions. AIMS Environmental Science, 2017, 4(6): 788-808. doi: 10.3934/environsci.2017.6.788


  • 1. Gattuso JP, Magnan A, Bille R, et al.(2015) Contrasting futures for ocean and society from different anthropogenic CO2 emissions scenarios. Science 349: aac4722.
  • 2. Sabine CL, Feely RA, Gruber N, et al. (2004) The oceanic sink for anthropogenic CO2. Science 305: 367-371.    
  • 3. IPCC Climate Change. Synthesis Report (2014) Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. In: R.K. Pachauri and L.A. Meyer, Ed. IPCC, Geneva, Switzerland.
  • 4. Engel A, Händel N, Wohlers J, et al. (2011) Effects of sea surface warming on the production and composition of dissolved organic matter during phytoplankton blooms: Results from a mesocosm study. J Plankton Res 33: 357-372.    
  • 5. Behrenfeld MJ, O'Malley RT, Siegel DA, et al. (2006) Climate-driven trends in contemporary ocean productivity. Nature 444: 752-755.    
  • 6. Bosc E, Bricaud A, Antoine D (2004) Seasonal and interannual variability in algal biomass and primary production in the Mediterranean Sea, as derived from 4 years of SeaWiFS observations. Global Biogeochem Cycles 18: 1-17.
  • 7. Hansell DA (2013) Recalcitrant dissolved organic carbon fractions. Ann Rev Mar Sci 5: 421-445.    
  • 8. Honjo S, Eglinton T, Taylor C, et al. (2014) Understanding the role of the biological pump in the global carbon cycle. An imperative for Ocean Science. Oceanogr 27: 10-16.
  • 9. Carlson CA, Hansell DA (2015) DOM: Sources, sinks, reactivity, and budgets. In: Hansell, D.A., Carlson C.A. Biogeochemistry of Marine Dissolved Organic Matter, 2 Eds., Boston Academic Press, 65-126.
  • 10. Agustí S, Duarte CM (2013) Phytoplankton lysis predicts dissolved organic carbon release in marine plankton communities. Biogeosciences 10: 1259-1264.    
  • 11. Ruiz-Halpern S, Duarte CM, Tovar-Sanchez A, et al. (2011) Antarctic krill as a source of dissolved organic carbon to the Antarctic ecosystem. Limnol Oceanogr 56: 521-528.    
  • 12. Wu Y, Gao K, Riebesell U (2010) CO2-induced seawater acidification affects physiological performance of the marine diatom Phaeodactylum tricornutum. Biogeosciences 7: 2915-2923.    
  • 13. Engel A, Zondervan I, Aerts K, et al. (2005) Testing the direct effect of CO2 concentration on a bloom of the coccolithophorid Emiliania huxleyi in mesocosm experiments. Limnol Oceanogr 50: 493-507.    
  • 14. Repeta DJ (2015) Chemical characterization and cycling of Dissolved Organic Matter. In: Hansell, D.A., Carlson C.A. Biogeochemistry of Marine Dissolved Organic Matter, 2 Eds., Boston Academic Press, 21-63.
  • 15. Benner R, Pakulski JD, McCarthy M, et al. (1992) Bulk chemical characteristics of dissolved organic matter in the Ocean. Science 255: 1561-1564.    
  • 16. Leenheer JA, Croué JP (2003) Characterizing aquatic dissolved organic matter. Environ Sci Technol 37: 18-26.    
  • 17. Benner R (2011) Loose ligands and available iron in the ocean. Proc Natl Acad Sci USA 108: 893-894.    
  • 18. Kaiser K, Benner R (2009) Biochemical composition and size distribution of organic matter at the Pacific and Atlantic time-series stations. Mar Chem 113: 63-77.    
  • 19. Hung CC, Guo L, Santschi PH, et al. (2003) Distributions of carbohydrate species in the Gulf of Mexico. Mar Chem 81: 119-135.    
  • 20. Hung CC, Tang D, Warnken KW, et al. (2001) Distributions of carbohydrates, including uronic acids, in estuarine waters of Galveston Bay. Mar Chem 73: 305-318.    
  • 21. Bourgoin LH, Tremblay L (2010) Bacterial reworking of terrigenous and marine organic matter in estuarine water columns and sediments. Geochim Cosmochim Acta 74: 5593-5609.    
  • 22. Jørgensen L, Lechtenfeld OJ, Benner R, et al. (2014) Production and transformation of dissolved neutral sugars and amino acids by bacteria in seawater. Biogeosciences 11: 5349-5363.    
  • 23. Piontek J, Borchard C, Sperling M, et al. (2013) Response of bacterioplankton activity in an Arctic fjord system to elevated pCO2: Results from a mesocosm perturbation study. Biogeosciences 10: 297-314.    
  • 24. Galgani L, Piontek J, Engel A (2016) Biopolymers form a gelatinous microlayer at the air-sea interface when Arctic sea ice melts. Sci Rep 6: 29465.    
  • 25. Underwood GJC, Aslam SN, Michel C, et al. (2013) Broad-scale predictability of carbohydrates and exopolymers in Antarctic and Arctic sea ice.Proc Natl Acad Sci USA 110: 15734-15739.
  • 26. Hassler CS, Alasonati E, Mancuso-Nichols CA, et al. (2011) Exopolysaccharides produced by bacteria isolated from the pelagic Southern Ocean - Role in Fe binding, chemical reactivity, and bioavailability. Mar Chem 123: 88-98.    
  • 27. Verdugo P, Alldredge AL, Azam F, et al. (2004) The oceanic gel phase: A bridge in the DOM-POM continuum. Mar Chem 92: 67-85.    
  • 28. Engel A, Thoms S, Riebesell U, et al. (2004) Polysaccharide aggregation as a potential sink of marine dissolved organic carbon. Nature 428: 929-932.    
  • 29. Stubbins A, Hubbard V, Uher G, et al. (2008) Relating carbon monoxide photoproduction to dissolved organic matter functionality. Environ Sci Technol 42: 3271-3276.    
  • 30. Li F, Pan B, Zhang D, et al. (2015) Organic matter source and degradation as revealed by molecular biomarkers in agricultural soils of Yuanyang terrace. Sci Rep 5: 11074.    
  • 31. Lu CJ, Benner R, Fichot CG, et al. (2016) Sources and transformations of dissolved lignin phenols and chromophoric dissolved organic matter in Otsuchi Bay, Japan. Front Mar Sci 3: 1-12.
  • 32. Klappe L, McKnight DM, Fulton JR, et al. (2002) Fulvic acid oxidation state detection using fluorescence spectroscopy. Environ Sci Technol 36: 3170-3175.    
  • 33. Helms JR, Mao J, Chen H, et al. (2015). Spectroscopic characterization of oceanic dissolved organic matter isolated by reverse osmosis coupled with electrodialysis. Mar Chem 177: 278-287.    
  • 34. López-Alarcón C, Denicola A (2013) Evaluating the antioxidant capacity of natural products: A review on chemical and cellular-based assays. Anal Chim Acta 763: 1-10.    
  • 35. Rico M, Santana-Casiano JM, González AG, et al. (2013) Variability of the phenolic profile in the diatom Phaeodactylum tricornutum growing under copper and iron stress. Limnol Oceanogra 51: 144-152.
  • 36. López A, Rico M, Santana-Casiano JM, et al. (2015) Phenolic profile of Dunaliella tertiolecta growing under high levels of copper and iron. Environ Sci Pollut Res 22: 14820-14828.    
  • 37. Elhabiri M, Carrër C, Marmolle F, et al. (2007) Complexation of iron(III) by catecholate-type polyphenols. Inorg Chim Acta 360: 353-359.    
  • 38. Sreeram KJ, Shrivastava HY, Nair BU (2004) Studies on the nature of interaction of iron(III) with alginates. Biochim Biophys Acta 1670: 121-125.    
  • 39. Santana-Casiano JM, González-Dávila M, González AG, et al. (2014) Characterization of phenolic exudates from Phaeodactylum tricornutum and their effects on the chemistry of Fe(II)-Fe(III). Mar Chem 158: 10-16.    
  • 40. Wu Y, Xiang W, Fu X, et al. (2016) Geochemical interactions between iron and phenolics originated from peatland in Hani, China: implications for effective transport of iron from terrestrial systems to marine. Environ Earth Sci 75: 336.    
  • 41. Hassler CS, Schoemann V (2009) Bioavailability of organically bound Fe to model phytoplankton of the Southern Ocean. Biogeosciences 6: 2281-2296.    
  • 42. Maldonado MT, Strzepek RF, Sander S, et al. (2005) Acquisition of iron bound to strong organic complexes, with different Fe binding groups and photochemical reactivities, by plankton communities in Fe-limited subantarctic waters. Global Biogeochem Cycles 19: Gb4S23.
  • 43. Hassler CS, Schoemann V, Nichols CM, et al. (2011) Saccharides enhance iron bioavailability to Southern Ocean phytoplankton. Proc Natl Acad Sci USA 108: 1076-1081.    
  • 44. Gordon RM, Martin JH, Knauer GA (1982) Iron in north-east Pacific waters. Nature 299: 611-612.    
  • 45. Heller MI, Wuttig K, Croot PL (2016) Identifying the Sources and Sinks of CDOM/FDOM across the Mauritanian Shelf and their potential role in the decomposition of superoxide (O2−). Front Mar Sci 3: 132.
  • 46. Hassler CS, Norman L, Mancuso-Nichols CA, et al. (2015) Iron associated with exopolymeric substances is highly bioavailable to oceanic phytoplankton. Mar Chem 173: 136-147.    
  • 47. Mueller B, den Haan J, Visser PM, et al. (2016) Effect of light and nutrient availability on the release of dissolved organic carbon (DOC) by Caribbean turf algae. Sci Rep 6: 23248.    
  • 48. Gunderson AR, Armstrong EJ, Stillman JH (2016) Multiple stressors in a changing world: The need for an improved perspective on physiological responses to the dynamic marine environment. Annu Rev Mar Sci 8: 357-378.    
  • 49. Jin P, Wang T, Liu N, et al. (2015) Ocean acidification increases the accumulation of toxic phenolic compounds across trophic levels. Nat Commun6: 8714.
  • 50. Lidbury I, Johnson V, Hall-Spencer JM, et al. (2012) Community-level response of coastal microbial biofilms to ocean acidification in a natural carbon dioxide vent ecosystem. Mar Pollut Bull 64: 1063-1066.    
  • 51. Borchard C, Engel A (2012) Organic matter exudation by Emiliania huxleyi under simulated future ocean conditions. Biogeosciences 9: 3405-3423.    
  • 52. Barofsky A, Vidoudez C, Pohnert G (2009) Metabolic profiling reveals growth stage variability in diatom exudates. Limnol Oceanogr Methods 7: 382-390.    
  • 53. Doney SC, Fabry VJ, Feely RA, et al. (2009) Ocean Acidification: The other CO2 problem. Annu Rev Mar Sci1: 169-192.
  • 54. Read BA, Kegel J, Klute MJ (2013) Pan genome of the phytoplankton Emiliania underpins its global distribution. Nature 499: 209-213.    
  • 55. Riebesell U, Fabry VJ, Hansson L, et al. (2010) Guide to best practices in Ocean Acidification research and data reporting. European Commisson, ISBN 9789279111181.
  • 56. Achterberg EP, Holland TW, Bowie AR, et al. (2001) Determination of iron in seawater. Anal Chim Acta, 442: 1-14.    
  • 57. González-Dávila M, Santana-Casiano JM, Rueda MJ, et al. (2010) The water column distribution of carbonate system variables at the ESTOC site from 1995 to 2004. Biogeosciences 7: 3067-3081.    
  • 58. Millero FJ, Graham TB, Huang F, et al. (2006) Dissociation constants of carbonic acid in seawater as a function of salinity and temperature. Mar Chem 100: 80-94.    
  • 59. Arístegui J, Duarte CM, Reche I, et al. (2014) Krill excretion boosts microbial activity in the Southern Ocean. PLoS ONE 9: e89391.    
  • 60. Arnow LE (1937) Colorimetric determination of the components of 3,4-dihydroxyphenylalaninetyrosine mixtures. J Biol Chem 118: 531-537.
  • 61. Myklestad SM, Skänoy E, Hestmann S (1997). A sensitive and rapid method for analysis of dissolved mono- and polysaccharides in nseawater. Mar Chem 56: 279-286.    
  • 62. Blumenkrantz N, Asboe-Hansen G (1973) New method for quantitative determination of uronic acids. Anal Biochem 54: 484-489.    
  • 63. Bastos R, Coelho E, Coimbra MA (2015) Modifications of Saccharomyces pastorianus cell wall polysaccharides with brewing process. Carbohydr Polym 124: 322-330.    
  • 64. Borchard C, Engel A (2015) Size-fractionated dissolved primary production and carbohydrate composition of the coccolithophore Emiliania huxleyi. Biogeosciences 12: 1271-1284.    
  • 65. Müller MN, Antia A, La Roche J (2008) Influence of cell cycle phase on calcification in the coccolithophore Emiliania huxleyi. Limnol Oceanogr 53: 506-512.    
  • 66. Daniels CJ, Sheward RM, Poulton AJ (2014) Biogeochemical implications of comparative growth rates of Emiliania huxleyi and Coccolithus species. Biogeosciences 11: 6915-6925.    
  • 67. Müller MN, Schulz KG, Riebesell U (2010) Effects of long-term high CO2 exposure on two species of coccolithophores. Biogeosciences 6: 10963-10982.
  • 68. Langer G, Nehrke G, Probert I, et al. (2009). Strain-specific responses of Emiliania huxleyi to changing seawater carbonate chemistry. Biogeosciences 6: 4361-4383.    
  • 69. Bach LT, Bauke C, Meier KJS, et al. (2012) Influence of changing carbonate chemistry on morphology and weight of coccoliths formed by Emiliania huxleyi. Biogeosciences 9: 3449-3463.    
  • 70. Meyer J, Riebesell U (2015) Reviews and syntheses: Responses of coccolithophores to ocean acidification: A meta-analysis. Biogeosciences 12: 1671-1682.    
  • 71. Rokitta SD, Rost B (2012) Effects of CO2 and their modulation by light in the life-cycle stages of the coccolithophore Emiliania huxleyi. Limnol Oceanogr 57: 607-618.    
  • 72. Sett S, Bach LT, Schulz KG, et al. (2014) Temperature modulates coccolithophorid sensitivity of growth, photosynthesis and calcification to increasing seawater pCO2. PLoS ONE 9: e0088308.
  • 73. Sciandra A, Harlay J, Lefèvre D, et al. (2003) Response of coccolithophorid Emiliania huxleyi to elevated partial pressure of CO2 under nitrogen limitation. Mar Ecol Prog Ser 261: 111-122.    
  • 74. Riegman R, Stolte W, Noordeloos AAM, et al. (2000) Nutrient uptake and alkaline phosphatase activity of Emiliania huxleyi (Prymnesiophyceae) during growth under N and P limitation in continuous cultures. J Phycol 36: 87-96.    
  • 75. Zondervan I (2007) The effects of light, macronutrients, trace metals and CO2 on the production of calcium carbonate and organic carbon in coccolithophoridores-A review. Deep-Sea Res Part II: Top Stud Oceanogr 54: 521-537.    
  • 76. Nielsdóttir MC, Moore CM, Sanders R, et al. (2009) Iron limitation of the postbloom phytoplankton communities in the Iceland Basin. Global Biogeochem Cycles 23: 1-13.
  • 77. Tagliabue A, Mtshali T, Aumont O, et al. (2012) A global compilation of dissolved iron measurements: Focus on distributions and processes in the Southern Ocean. Biogeosciences 9: 2333-2349.    
  • 78. Sherr EB, Sherr BF, Wheeler PA (2005) Distribution of coccoid cyanobacteria and small eukaryotic phytoplankton in the upwelling ecosystem off the Oregon coast during 2001 and 2002. Deep-Sea Res Part II: Top Stud Oceanogr 52: 317-330.    
  • 79. Alexov EG, Gunner MR (1997) Incorporating protein conformational flexibility into the calculation of pH-dependent protein properties. Biophys J 72: 2075-2093.    
  • 80. Riebesell U, Schulz KG, Bellerby RGJ, et al. (2007) Enhanced biological carbon consumption in a high CO2 ocean. Nature 450: 545-548.    
  • 81. MacGilchrist GA, Shi T, Tyrrell T, et al. (2014) Effect of enhanced pCO2 levels on the production of dissolved organic carbon and transparent exopolymer particles in short-term bioassay experiments. Biogeosciences 11: 3695-3706.    
  • 82. Paul AJ, Bach LT, Schulz KG, et al. (2015) Effect of elevated CO2 on organic matter pools and fluxes in a summer Baltic Sea plankton community. Biogeosciences 12: 6181-6203,.    
  • 83. Yoshimura T, Suzuki K, Kiyosawa H, et al. (2013) Impacts of elevated CO2 on particulate and dissolved organic matter production: Microcosm experiments using iron-deficient plankton communities in open subarctic waters. J Oceanogr 69: 601-618.    
  • 84. Thornton DCO (2014) Dissolved organic matter (DOM) release by phytoplankton in the contemporary and future ocean . Eur J Phycol 49: 20-46.    
  • 85. Spilling K, Schulz KG, Paul AJ, et al. (2016) Effects of ocean acidification on pelagic carbon fluxes in a mesocosm experiment. Biogeosciences 13: 6081-6093.    
  • 86. Becker JW, Berube PM, Follett CL, et al. (2014) Closely related phytoplankton species produce similar suites of dissolved organic matter. Front Microbio 5: 1-14.
  • 87. Underwood GJC, Boulcott M, Raines CA, et al. (2004) Environmental effects on exopolymeric production by marine benthic diatoms: Dynamics, changes in composition and pathways of production. J Phycol 40: 293-304.    
  • 88. Wetz MS, Wheeler PA (2007). Release of dissolved organic matter by coastal diatoms. Limnol Oceanogr 52: 798-807.    
  • 89. Van Oostende N, Moerdijk-Poortvliet TCW, Boschker HTS, et al. (2013) Release of dissolved carbohydrates by Emiliania huxleyi and formation of transparent exopolymer particles depend on algal life cycle and bacterial activity. Environ Microbio 15: 1514-1531.    
  • 90. Biddanda B, Benner R (1997) Carbon, nitrogen, and carbohydrate fluxes during the production of particulate and dissolved organic matter by marine phytoplankton. Limnol Oceanogr 42: 506-518.    
  • 91. Engel A, Piontek J, Grossart HP, et al. (2014) Impact of CO2 enrichment on organic matter dynamics during nutrient induced coastal phytoplankton blooms. J Plankton Res 36: 641-657.    
  • 92. Song C, Ballantyne IVF, Smith VH (2014) Enhanced dissolved organic carbon production in aquatic ecosystems in response to elevated atmospheric CO2. Biogeochem 118: 49-60.    
  • 93. Zubia M, Payri C, Deslandes E (2016) Alginate, mannitol, phenolic compounds and biological activities of two range-extending brown algae, Sargassum mangarevense and Turbinaria ornata (Phaeophyta: Fucales), from Tahiti (French Polynesia). J Appl Phycol 20: 1033-1043.
  • 94. Celis-Plá PSM, Bouzon ZL, Hall-Spencer JM, et al. (2016) Seasonal biochemical and photophysiological responses in the intertidal macroalga Cystoseira tamariscifolia (Ochrophyta). Mar Environ Res 115: 89-97.    
  • 95. Huang JJH, Xu WW, Lin SL, et al. (2016) Phytochemical profiles of marine phytoplanktons: an evaluation of their in vitro antioxidant and anti-proliferative activities. Food Funct 7: 5002-5017.    
  • 96. Celis-Plá PSM, Hall-Spencer JM, Horta PA, et al. (2015) Macroalgal responses to ocean acidification depend on nutrient and light levels. Front Mar Sci 2: 1-12.
  • 97. Shi D, Xu Y, Hopkinson BM, et al. (2010) Effect of ocean acidification on iron availability to marine phytoplankton. Science 327: 676-679.    
  • 98. Gledhill M, McCormack P, Ussher S, et al. ( 2004) Production of siderophore type chelates by mixed bacterioplankton populations in nutrient enriched seawater incubations. Mar Chem 88: 75-83.
  • 99. Kranzler C, Lis H, Finkel OM, et al. (2014) Coordinated transporter activity shapes high-affinity iron acquisition in cyanobacteria. ISME J 8: 409-417.    
  • 100. Manwar AV, Khandelwal SR, Chaudhari BL, et al. (2004) Siderophore production by a marine Pseudomonas aeruginosa and its antagonistic action against phytopathogenic fungi. Appl Biochem Biotechnol 118: 243-251.    
  • 101. Urbani R, Magaletti E, Sist P, et al. (2005) Extracellular carbohydrates released by the marine diatoms Cylindrotheca closterium, Thalassiosira pseudonana and Skeletonema costatum: Effect of P-depletion and growth status. Sci Total Environ 353: 300-306.    
  • 102. Khodse VB, Bhosle NB, Matondkar SGP (2010) Distribution of dissolved carbohydrates and uronic acids in a tropical estuary, India. J Earth Syst Sci 119: 519-530.    
  • 103. Ozturk S, Aslim B, Suludere Z, et al. (2014) Metal removal of cyanobacterial exopolysaccharides by uronic acid content and monosaccharide composition. Carbohydr Polym 101: 265-271.    
  • 104. Hutchins DA, Boyd PW (2016) Marine phytoplankton and the changing ocean iron cycle. Nat Clim Change 6: 1072-1079,    
  • 105. Geider RJ, La Roche J (1994) The role of iron in phytoplankton photosynthesis, and the potential for iron-limitation of primary productivity in the sea. Photosynth Res 39: 275-301.    
  • 106. Hoffmann LJ, Breitbarth E, Boyd PW, et al. (2012) Influence of ocean warming and acidification on trace metal biogeochemistry. Mar Ecol Prog Ser 470: 191-205.    


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