Articles | Volume 4, issue 4
Biogeosciences, 4, 613–626, 2007
https://doi.org/10.5194/bg-4-613-2007
Biogeosciences, 4, 613–626, 2007
https://doi.org/10.5194/bg-4-613-2007

  08 Aug 2007

08 Aug 2007

Different carbon isotope fractionation patterns during the development of phototrophic freshwater and marine biofilms

M. Staal1,*, R. Thar2, M. Kühl2, M. C. M. van Loosdrecht3, G. Wolf3, J. F. C. de Brouwer1, and J. W. Rijstenbil1,** M. Staal et al.
  • 1Department of Marine Microbiology, Netherlands Institute of Ecology – KNAW, P.O. Box 140, 4400 AC Yerseke, The Netherlands
  • 2Marine Biological Laboratory, Institute of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark
  • 3Department of Environmental Biotechnology, TU Delft, Julianalaan 67, 2628 BC Delft, The Netherlands
  • *present address: Marine Biological Laboratory, Institute of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark
  • **present address: AE3 Consultancy, Fuchsialaan 8, 4401HV Yerseke, The Netherlands

Abstract. Natural phototrophic biofilms are influenced by a broad array of abiotic and biotic factors and vary over temporal and spatial scales. Different developmental stages can be distinguished and growth rates will vary due to the thickening of the biofilm, which is expected to lead to a limitation of light or mass transport. This study shows that variation in CO2(aq) availability leads to a fractionation shift and thereby affects δ13C signatures during biofilm development. For phototrophic freshwater biofilms it was found that the δ13C value became less negative with the thickening of the biofilm, while the opposite trend was found in marine biofilms. Modeling and pH profiling indicated that the trend in the freshwater system was caused by an increase in CO2(aq) limitation resulting in an increase of HCO3 as C-source. The opposite trend in the marine system could be explained by a higher heterotrophic biomass and activity causing a higher carbon recycling and thereby lower δ13C values. We conclude that δ13C was more related to the net areal photosynthesis rate and carbon recycling, rather than to the growth rate of the biofilms.

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