, Volume 108, Issue 1–3, pp 109–118 | Cite as

pH change induces shifts in the size and light absorption of dissolved organic matter

  • Michael L. Pace
  • Isabel Reche
  • Jonathan J. Cole
  • Antonio Fernández-Barbero
  • Ignacio P. Mazuecos
  • Yves T. Prairie


Dissolved organic matter (DOM) influences inland water ecosystems through its light absorbing qualities. We investigated how pH affects light absorption by DOM with pH manipulation experiments and with data from two lake surveys. We hypothesized that: (1) light absorption and photobleaching of DOM would increase with increasing pH, and (2) as a result of photobleaching, molar absorption (i.e. light absorbance at 440 nm/dissolved organic carbon concentration) would decrease among lakes with increasing pH. In experiments with filtered lake water both initial light absorption and photobleaching rates increased at higher (i.e. more basic) pH along with a concomitant shift in the size of DOM toward larger colloidal materials measured by dynamic light scattering (DLS). Both scanning electron microscopy (SEM) and atom force microscopy (AFM) revealed large colloidal to particulate-sized organic matter in alkaline relative to acidic treatments. In the lake surveys, molar absorption coefficients were negatively related to pH across gradients similar to the experiments. Our results are consistent with a conceptual model in which at low pH DOM polymers and colloids are condensed limiting exposure of chromophores to light; at higher pH, polymers and colloids are expanded exposing chromophores to light resulting in greater initial light absorption and faster photobleaching. Hence, water transparency, which is significantly controlled by DOM, is sensitive to environmental changes that influence the pH and chemical composition of inland waters.


Dissolved organic matter Light absorption pH Lakes Photobleaching Colloids CDOM 



We thank D. Thomas, S. Scanga, M. Van de Bogert, and J Coloso for help in the lab and field. E. Urea helped with microscopy, and F. Perfectti helped with the conceptual figure. Comments by two anonymous reviewers improved the final version of this paper. Our research was supported by grants from the National Science Foundation, USA (DEB0716869, DEB0715054), Spanish Ministry of Science and Technology (DISPAR, CGL2005-000076, MAT2009-14234-C03-02), Andalusian Research Ministry (Excellence Project FQM230-2009), and the National Research Council of Canada.


  1. Aiken GR, Malcolm RL (1987) Molecular weight of aquatic fulvic acids by vapor pressure osmometry. Geochim Cosmochim Acta 51:2177–2184CrossRefGoogle Scholar
  2. Baalousha M, Motelica-Heino M, Coustumer PL (2006) Conformation and size of humic substances: effects of major cation concentration and type, pH, salinity, and residence time. Colloids Surface A Physicochem Eng Aspects 272:48–55CrossRefGoogle Scholar
  3. Bricaud A, Morel A, Prieur L (1981) Absorption by dissolved organic-matter of the sea (yellow substance) in the UV and visible domains. Limnol Oceanogr 26:43–53CrossRefGoogle Scholar
  4. Carignan R, Perceval O, Prairie YT, Parkes A. (2007) Développement d’un outil de prévention de l’eutrophisation des lacs des Laurentides et de L’Estrie. Report to the Ministère du Développement durable et des ParcsGoogle Scholar
  5. Chin W-C, Orellana MC, Verdugo P (1998) Spontaneous assembly of marine dissolved organic matter into polymer gels. Nature 391:568–572CrossRefGoogle Scholar
  6. Cole JJ, Prairie YT, Caraco NF, McDowell WH, Tranvik LJ, Striegl RG, Duarte CM, Kortelainen P, Downing JA, Middelburg JJ, Melack J (2007) Plumbing the global carbon cycle: integrating inland waters into the terrestrial carbon budget. Ecosystems 10:171–184CrossRefGoogle Scholar
  7. Cuthbert D, del Giorgio P (1992) Toward a standard method of measuring color in freshwater. Limnol Oceanogr 37:1319–1326CrossRefGoogle Scholar
  8. de Vincente I, Ortega-Reuerta E, Romera O, Morales-Baquero R, Reche I (2009) Contribution of transparent exopolymer particles to carbon sinking flux in an oligotrophic reservoir. Biogeochemistry. doi: 10:1007/s10533-009-9342-8
  9. De Wit HA, Mulder J, Hindar A, Hole L (2007) Long-term increase in dissolved organic carbon in streamwaters in Norway in response to reduced acid deposition. Environ Sci Technol 41:7706–7713CrossRefGoogle Scholar
  10. Del Vecchio R, Blough NV (2002) Photobleaching of chromophoric dissolved organic matter in natural waters: kinetics and modeling. Mar Chem 78:231–253CrossRefGoogle Scholar
  11. Findlay S, McDowell WH, Fischer D, Pace ML, Caraco N, Kaushal SS, Weathers KC (2010) Total carbon analysis may overestimate organic carbon content of fresh waters in the presence of high dissolved inorganic carbon. Limnol Oceanogr Methods 8:196–201Google Scholar
  12. Friskin BJ (2001) Revisiting the method of cumulants for the analysis of dynamic light-scatter data. Appl Optics 40:4087–4091CrossRefGoogle Scholar
  13. Karlsson J, Bystrom P, Ask J, Ask P, Persson L, Jansson M (2009) Light limitation of nutrient poor lake ecosystems. Nature 460:506–509CrossRefGoogle Scholar
  14. Kelton N, Molot LA, Dillon PJ (2007) Spectrofluorometric properties of dissolved organic matter from central and southern Ontario streams. Water Res 41:638–646CrossRefGoogle Scholar
  15. Kirk JTO (1994) Light and photosynthesis in aquatic ecosystems. Cambridge University Press, CambridgeCrossRefGoogle Scholar
  16. Koppel DE (1972) Analysis of macromolecular polydispersity in intensity correlation spectroscopy: the method of cumulants. J Chem Phys 57:4814–4820. doi: 10.1063/1.1678153 CrossRefGoogle Scholar
  17. Lindell MJ, Graneli W, Tranvik LJ (1995) Enhanced bacterial growth in response to photochemical transformation of dissolved organic matter. Limnol Oceanogr 40:195–199CrossRefGoogle Scholar
  18. McKnight DM, Boyer EW, Westerhoff PK, Doran PT, Kulbe T, Andersen DT (2001) Spectrofluorometric characterization of dissolved organic matter for indication of precursor organic material and aromaticity. Limnol Oceanogr 46:38–48CrossRefGoogle Scholar
  19. Miller WL (1998) Effects of UV radiation on aquatic humus: photochemical principles and experimental considerations. In: Hessen DO, Tranvik LJ (eds) Aquatic humic substances: ecology and biogeochemistry. Springer-Verlag, New YorkGoogle Scholar
  20. Molot LA, Dillon PJ (1997) Photolytic regulation of dissolved organic carbon in northern lakes. Global Biogeochem Cycle 11:357–365CrossRefGoogle Scholar
  21. Molot LA, Hudson JJ, Dillon PJ, Miller SA (2005) Effect of pH on photo-oxidation of dissolved organic carbon by hydroxyl radicals in a coloured softwater stream. Aquat Sci 67:189–195CrossRefGoogle Scholar
  22. Monteith DT et al (2007) Dissolved organic carbon trends resulting from changes in atmospheric deposition chemistry. Nature 450:537–539CrossRefGoogle Scholar
  23. Morris DP, Hargreaves BR (1997) The role of photochemical degradation of dissolved organic carbon in regulating the UV transparency of three lakes on the Pocono Plateau. Limnol Oceanogr 42:239–249CrossRefGoogle Scholar
  24. Morris DP, Zagarese H, Williamson CE, Balseiro EG, Hargreaves BR, Modenutti B, Moeller R, Queimalinos XX (1995) The attenuation of solar UV radiation in lakes and the role of dissolved organic carbon. Limnol Oceanogr 40:1381–1391CrossRefGoogle Scholar
  25. Myneni SCB, Brown JT, Martinez GA, Meyer-Ilse W (1999) Imaging of humic substance macromolecular structures in water and soils. Science 286:1335–1337CrossRefGoogle Scholar
  26. Osburne CL, Zagarese HE, Morris DP, Hargreaves BR, Cravero WE (2001) Calculation of spectral weighting functions for the solar photobleaching of chromophoric dissolved organic matter in temperate lakes. Limnol Oceanogr 46:1455–1467CrossRefGoogle Scholar
  27. Otsuki A, Wetzel RG (1973) Interaction of yellow organic acids with calcium carbonate in freshwater. Limnol Oceanogr 18:490–493CrossRefGoogle Scholar
  28. Pace ML, Cole JJ (2002) Synchronous variation of dissolved organic carbon in lakes. Limnol Oceanogr 47:333–342CrossRefGoogle Scholar
  29. Prairie YT (2008) Carbocentric limnology: looking back, looking forward. Can J Fish Aquat Sci 65:54–548CrossRefGoogle Scholar
  30. Reche I, Pace ML, Cole JJ (1998) Interactions of photobleaching and inorganic nutrients in determining bacterial growth on colored dissolved organic carbon. Microb Ecol 36:270–280CrossRefGoogle Scholar
  31. Reche I, Pace ML, Cole JJ (1999) Relationship of trophic and chemical conditions to photobleaching of dissolved organic matter in lake ecosystems. Biogeochemistry 44:259–280Google Scholar
  32. Reche I, Pulido-Villena E, Conde-Porcuna JM, Carrillo P (2001) Photoreactivity of dissolved organic matter from high-mountain lakes of Sierra Nevada, Spain. Arct Antarct Alp Res 33:426–434CrossRefGoogle Scholar
  33. Santschi PH, Balnois E, Wilkinson K, Zhang J, Buffle J, Guo L (1998) Fibrillar polysaccharides in marine macromolecular organic matter, as imaged by atomic force microscopy and transmission electron microscopy. Limnol Oceanogr 43:896–908CrossRefGoogle Scholar
  34. Tranvik LJ, Jansson M (2002) Climate change—export of organic carbon. Nature 415:861–862CrossRefGoogle Scholar
  35. Tranvik LJ et al (2009) Lakes and reservoirs as regulators of carbon cycling and climate. Limnol Oceanogr 54:2298–2314CrossRefGoogle Scholar
  36. Tzortziou M, Osburn CL, Neale PJ (2007) Photobleaching of dissolved organic material from tidal marsh-estuarine system of the Chesapeake Bay. Photochem Photobiol 83:782–792CrossRefGoogle Scholar
  37. Verdugo P, Alldredge AL, Azam F, Kirchman DL, Passow U, Santschi PH (2004) The oceanic gel phase: a bridge in the DOM-POM continuum. Mar Chem 92:67–85CrossRefGoogle Scholar
  38. von Wachenfeldt E, Tranvik LJ (2008) Sedimentation in boreal lakes—the role of flocculation of allochthonous dissolved organic matter in the water column. Ecosystems 11:803–814CrossRefGoogle Scholar
  39. Wetzel RG (2001) Limnology: lake and river ecosystems. Academic Press, BurlingtonGoogle Scholar
  40. Wetzel RG, Hatcher PG, Bianchi TS (1995) Natural photolysis by ultraviolet irradiance of recalcitrant dissolved organic matter to simple substrates for rapid bacterial metabolism. Limnol Oceanogr 40:1369–1380CrossRefGoogle Scholar
  41. Williamson CE, Morris DP, Pace ML, Olson OG (1999) Dissolved organic carbon and nutrients as regulators of lake ecosystems: resurrection of a more integrated paradigm. Limnol Oceanogr 44:795–803CrossRefGoogle Scholar
  42. Wilson HF, Xenopoulos MA (2009) Effects of agricultural land use on the composition of fluvial dissolved organic matter. Nat Geosci 2:37–41CrossRefGoogle Scholar
  43. Zepp RG, Faust BC, Hoigné J (1992) Hydroxyl radical formation in aqueous reactions (pH 3–8) of iron (II) with hydrogen-peroxide: the photo-Fenton reaction. Environ Sci Technol 26:313–319CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • Michael L. Pace
    • 1
  • Isabel Reche
    • 2
  • Jonathan J. Cole
    • 3
  • Antonio Fernández-Barbero
    • 4
  • Ignacio P. Mazuecos
    • 2
    • 4
  • Yves T. Prairie
    • 5
  1. 1.Department of Environmental SciencesUniversity of VirginiaCharlottesvilleUSA
  2. 2.Departamento de EcologiaUniversidad de GranadaGranadaSpain
  3. 3.Cary Institute of Ecosystem StudiesMillbrookUSA
  4. 4.Departamento de Fisica AplicadaUniversidad de AlmeriaAlmeriaSpain
  5. 5.Département des Sciences BiologiquesUniversité du Québec à MontréalMontrealCanada

Personalised recommendations