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Biogeochemistry

, Volume 47, Issue 2, pp 167–186 | Cite as

Origin and fate of organic carbon in the freshwater part of the Scheldt Estuary as traced by stable carbon isotope composition

  • L. Hellings
  • F. Dehairs
  • M. Tackx
  • E. Keppens
  • W. Baeyens
Article

Abstract

We investigated the seasonal and geographical variation in the stable carbon isotope ratios of total dissolved inorganic carbon (δ13CPOC) and suspended matter (δ13CPOC) in the freshwater part of the River Scheldt. Two major sources of particulate organic matter (POM) occur in this riverine system: riverine phytoplankton and terrestrial detritus. In winter the lowest δ13CDIC values are observed due to enhanced input of CO2 from decomposition of 13C-depleted terrestrial plant detritus (average δ13CDIC = −/14.3‰). During summer, when litter input from terrestrial flora is the lowest, water column respiration on POM of terrestrial origin is also the lowest as evidenced by less negative δ13CDIC values (average δ13CDIC = −9.9‰). In winter the phytoplankton biomass is low, as indicated by low chlorophyll a concentrations (Chl a < 4.5 μgl−1), compared to summer when chlorophyll a concentrations can rise to a maximum of 54 μgl−1. Furthermore, in winter the very narrow range of δ13CPOC (from −26.5 to −27.6‰) is associated with relatively high C/N ratios (C/N > 9) suggesting that in winter a major fraction of POC is derived from allochthonous matter. In summer δ13CPOC exhibits a very wide range of values, with the most negative values coinciding with high Chl a concentrations and low C/N ratios (C/N < 8). This suggests predominance of phytoplankton carbon in the total particulate carbon pool, utilising a dissolved inorganic carbon reservoir, which is already significantly depleted in 13C. Using a simple two source mixing approach a reconstruction of the relative importance of phytoplankton to the total POC pool and of 13C/12C fractionation by phytoplankton is attempted.

Zeeschelde stable carbon isotopes dissolved inorganic carbon particulate organic carbon 

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References

  1. Baeyens W, Van Eck B, Lambert C, Wollast R & Goeyens L (1998) General description of the Scheldt Estuary. Hydrobiologia 366: 1-14Google Scholar
  2. Billen G, Lancelot C, De Becker E & Servais P (1988) Modelling microbial processes (phytoand bacterioplankton) in the Schelde Estuary. Hydrobiological Bulletin 22: 43-55Google Scholar
  3. Billiones R (1998) Spatio-temporal distribution of suspended particulate matter in the Scheldt estuary (Belgium) and interactions with mesozooplankton. Doctoral Thesis, Vrije Universiteit Brussel, BelgiumGoogle Scholar
  4. Boutton TW (1991) Stable carbon isotope ratios of natural materials: II. Atmospheric, terrestrial, marine, and freshwater environments. In: Carbon Isotope Techniques (pp 173-184). Academic PressGoogle Scholar
  5. Cai DL, Tan FC & Edmond JM (1988) Sources and transport of particulate organic carbon in the Amazon River and estuary. Estuarine, Coastal and Shelf Science 26: 1-14Google Scholar
  6. Cifuentes LA, Sharp JH & Fogel ML (1988) Stable carbon and nitrogen isotope biogeochemistry in the Delaware estuary. Limnology and Oceanography 33(5): 1102-1115Google Scholar
  7. Coffin RB, Cifuentes LA & Elderidge PM (1994) The use of stable carbon isotopes to study microbial processes in estuaries. In: Lajtha & Michener (Eds) Methods in Ecology: Stable Isotopes in Ecology and Environmental Science (pp 222-240)Google Scholar
  8. Coplen TB (1996) New guidelines for reporting stable hydrogen, carbon and oxygen isotoperatio data. Geochimica et Cosmochimica Acta 60: 3359-3360Google Scholar
  9. Farquhar GD, Ehlinger JR & Hubick KT (1989) Carbon istope discrimination and photosynthesis. Annual Review of Plant Physiology and Plant Molecular Biology 40: 503-537Google Scholar
  10. Frankignoulle M, Bourge I & Wollast R (1996) Atmospheric CO2 fluxes in a highly polluted estuary (the Scheldt). Limnology and Oceanography 41(2): 365-369Google Scholar
  11. Fry B & Sherr EB (1984) δ 13C measurements as indicators of carbon flow in marine and freshwater ecosystems. Contributions in Marine Science 27: 13-47Google Scholar
  12. Geider RJ (1987) Light and temperature dependence of the carbon to chlorophyll a ratio in microalgae and cyanobacteria: Implications for physiology and growth of phytoplankton. New Phytol. 106: 1-34Google Scholar
  13. Goosen NK, Rijswijk P Van & Brockmann U (1995) Comparison of heterotrophic bacterial production rates in early spring in the turbid estuaries of the Scheldt and the Elbe. Hydrobiologia 311: 31-42Google Scholar
  14. Heip C (1988) Biota and abiotic environment in the Westerschelde estuary. Hydrobiological Bulletin 22: 31-34Google Scholar
  15. Keeley JE & Sandquist DR (1992) Carbon: Freshwater plants. Plant, Cell and Environment 15: 1021-1035Google Scholar
  16. Kroopnick P. (1974) Correlations between 13C and ΣCO2 in surface waters and atmospheric CO2. Earth Planetary Science Letters 22: 397-403Google Scholar
  17. Marguillier S, Van der Velde G, Dehairs F, Hemminga MA & Rajagopal S (1997) Tropic relationships in an interlinked mangrove-seagrass ecosystem as traced by δ 13C and δ 15N. Marine Ecology Progress Series 151: 115-121Google Scholar
  18. Meire P, Ysebaert T, Hoffmann M, Van Den Balk E, Debos K, Samanya R, Deregge N, Van Waeyenberge J, Anselin A, Rossaert G & Kuijken E (1994) Ecologisch onderzoek in de Zeeschelde door het instituut voor natuurbehoud: onderbouwing van natuurherstel en natuurontwikkeling. Biologisch Jaarboek, Dodonaea 62: 27-47Google Scholar
  19. Meire P, Hoffman M & Ysebaert T (1995) De Schelde: een stroom natuurtalent. Instituut voor Natuurbehoud, Hasselt: Rapport 95.10.Google Scholar
  20. Middelburg JJ, Klaver G, Nieuwenhuize J & Vlug T (1995) Carbon and nitrogen cycling in intertidal sediments near Doel, Scheldt Estuary. Hydrobiologia 311: 57-69Google Scholar
  21. Middelburg J & Nieuwenhuize J (1998) Carbon and nitrogen stable istopes in suspended matter and sediments from the Schelde Esstuary. Marine Chemistry 60: 217-225Google Scholar
  22. Mook WG (1970) Stable carbon and oxygen isotopes of natural waters in the Netherlands. In: Proceedings IAEA Conference on Isotopes in Hydrology, Vienna (pp 163-190)Google Scholar
  23. Mook WG, Bommerson JC & Staverman WH (1974) Carbon isotope fractionation between dissolved bicarbonate and gaseous carbon dioxide. Earth and Planetary Science Letters 22: 169-176Google Scholar
  24. Mook WG & Tan TC (1991) Stable carbon isotopes in rivers and estuaries. In: Degens ET, Kempe S & Richey JE (Eds) Biogeochemistry of Major World Rivers (pp 245-264). SCOPE, John Wiley and Sons LtdGoogle Scholar
  25. Muylaert K, Van Kerckvoorde A, Vyverman W & Sabbe K (1997) Structural characteristics of phytoplankton assemblages in tidal and non-tidal freshwater systems: A case study from the Schelde basin, Belgium. Freshwater Biology 38: 263-276Google Scholar
  26. Ostrom NE, Macko SA, Deibel D & Thompson RJ (1997) Seasonal variation in the stable carbon and nitrogen isotope biogeochemistry of a coastal cold ocean environment. Geochimica et Cosmochimica Acta 61(14): 2929-2942Google Scholar
  27. Quay PD, Emerson SR, Quay BM & Devol AH (1986) The carbon cycle for Lake Washington — A stable isotope study. Limnology and Oceanography 31(3): 596-611Google Scholar
  28. Quay PD, Wilbur DO & Richey JE (1992) Carbon cycling in the Amazon River: Implications from the 13C compositions of particles and solutes. Limnology and Oceanography 37(4): 857-871Google Scholar
  29. Redfield AC, Ketchum BH & Richards FA (1963) The influence of organisms on the composition of seawater. In: Hill MN (Ed) The Sea, Vol. 2 (pp 26-77). Wiley, New YorkGoogle Scholar
  30. Ronday F (1976) Modèles hydrodynamiques. In: Nihoul JCJ (Ed) Projet Mer, Rapport Final, Le Ministère de la Programmation de la Politique Scientifique, Brussels, Vol. 3Google Scholar
  31. Soetaert K & Herman PMJ (1994a) Estimating estuarine residence times in the Westerschelde (The Netherlands) using a box model with fixed dispersion coefficients. Hydrobiologia 311(1/3): 215-224Google Scholar
  32. Tan FC & Strain PM (1983) Sources, sinks and distribution of organic carbon in the St. Lawrence Estuary, Canada. Geochimica et Cosmochimica Acta 47: 125-132Google Scholar
  33. Wollast R & Duinker JC (1982) General methodology and sampling strategy for studies on the behaviour of chemicals in estuaries. Thalassia Jugoslavica 18: 471-491Google Scholar
  34. Wollast R. (1983) Interactions in estuaries and coastal waters. In: Bolin B & Cook RB (Eds) The Major Biogeochemical Cycles and Their Interactions, SCOPE 21 (pp 385-407). Wiley-InterscienceGoogle Scholar
  35. Wollast R (1988) The Scheldt Estuary. In: Saloms et al. (Eds) Pollution of the North Sea: An Assessment (pp 185-193). SpringerGoogle Scholar

Copyright information

© Kluwer Academic Publishers 1999

Authors and Affiliations

  • L. Hellings
    • 1
  • F. Dehairs
    • 1
  • M. Tackx
    • 2
  • E. Keppens
    • 3
  • W. Baeyens
    • 1
  1. 1.Department of Analytical ChemistryVrije Universiteit BrusselBrusselsBelgium
  2. 2.Department of Ecology and SystematicsVrije Universiteit BrusselBrusselsBelgium
  3. 3.Department of GeologyVrije Universiteit BrusselBrusselsBelgium

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