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Carbon flux between an estuary and the ocean: a case for outwelling

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Abstract

The classical outwelling hypothesis states that small coastal embayments (e.g. estuaries, wetlands) export their excess production to inshore marine waters. In line with this notion, the present study tested whether the Swartkops estuary acts as source or sink for carbon. To this end, concentrations of dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and particulate organic carbon (POC) were determined hourly during the first monthly spring and neap tides over one year in the tidal waters entering and leaving the estuary. Each sampling session spanned a full tidal cycle, yielding a total of 936 concentration estimates. Carbon fluxes were calculated by integrating concentrations with water flow rates derived from a hydrodynamic model calibrated for each sampling datum. Over the year, exports to marine waters markedly exceeded imports to the estuary for all carbon species: on the basis of total spring tidal drainage area, 1083 g m−2 of DIC, 103 g m−2 of DOC, and 123 g m−2 of POC left the estuary annually. Total carbon export from the estuary to the ocean amounted to 4755 tonnes, of which 83% was in the inorganic form (DIC). Thus, the bulk of carbon moving in the water column is inorganic - yet, DIC seems to be measured only rarely in most flux studies of this nature. Salt marshes cover extensive areas in this estuary and produce some carbon, particularly DOC, but productivity of the local Spartina species is low (P:B=1.1). Consequently, the bulk of carbon exported from the estuary appears to originate from the highly productive macroinvertebrate and the phytoplankton component and not from the salt marsh plants.

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References

  • Baird, D., 1988. Synthesis of ecological research in the Swartkops estuary. In D. Baird, J. F. K. Marais & A. P. Martin (eds), The Swartkops Estuary. South African National Scientific Programmes Report No. 156, C.S.I.R.: 41–56.

  • Baird, D., P. E. D. Winter & G. Wendt, 1987. The flux of particulate material through a well-mixed estuary. Cont. Shelf Res. 7: 1399–1403.

    Article  Google Scholar 

  • Borey, R. B., P. A. Harcombe & F. M. Fischer, 1983. Water and organic carbon fluxes from an irregularly flooded brackish marsh on the Upper Texas coast, USA. Est. Coast. Shelf Sci. 16: 379–402.

    Article  CAS  Google Scholar 

  • Boto, K. G. & J. S. Bunt, 1981. Tidal export of particulate organic matter from a Northern Australian mangrove system. Est. Coast. Shelf Sci. 13: 247–255.

    Article  Google Scholar 

  • Branch, G. M. & J. A. Day, 1984. Ecology of Southern African estuaries: Part XIII. The Pahniet River estuary in the south-western Cape. S. Afr. J. Zool. 19: 63–77.

    Google Scholar 

  • Brown, J., A. Colling, D. Park, J. Phillips, D. Rothery & J. Wright (Open University. Oceanography Course Team), 1989. Waves, Tides and Shallow-water Processes. Pergamon Press, Oxford: 187 pp.

    Google Scholar 

  • Chrzanowski, T. H., L. H. Stevenson & J. D. Spurrier, 1982. Transport of particulate organic carbon through the North Inlet ecosystem. Mar. Ecol. Prog. Ser. 7: 231–245.

    Article  Google Scholar 

  • Daly, M. A. & A. C. Mathieson, 1981. Nutrient fluxes within a small north temperate salt marsh. Mar. Biol. 61: 337–344.

    Article  CAS  Google Scholar 

  • Dame, R., T. Chrzanowski, K. Bildstein, B. Kjerfve, H. McKellar, D. Nelson, J. Spurrier, S. Stancyk, H. Stevenson, J. Vemberg & R. Zingmark, 1986. The outwelling hypothesis and North Inlet, South Carolina. Mar. Ecol. Prog. Ser. 33: 217–229.

    Article  Google Scholar 

  • Dame, R., D. Childers & E. Koepfler, 1992. A geohydrologic continuum theory for the spatial and temporal evolution of marsh-estuarine ecosystems. Neth. J. Sea Res. 30: 63–72.

    Article  Google Scholar 

  • Dye, A. H., 1978. Epibenthic algal production in the Swartkops estuary. Zool. Afr. 13: 157–161.

    Article  Google Scholar 

  • Els, S., 1982. Distribution and abundance of two crab species on the Swartkops estuary salt marshes and the energetics of the Sesarma catenata population. M. Sc. Thesis, University of Port Elizabeth.

  • Hanekom, N., D. Baird & T. Erasmus, 1988. A quantitative study to assess standing biomasses of macrobenthos in soft substrata of the Swartkops estuary, South Africa. S. Afr. J. mar. Sci. 6: 163–174.

    Article  Google Scholar 

  • Hardisky, M. A. & R. J. Reimold, 1977. Salt marsh plant geratology. Science 198: 612–614.

    Article  CAS  Google Scholar 

  • Heinle, D. R. & D. A. Flemer, 1976. Flow of materials between poorly flooded tidal marshes and an estuary. Mar. Biol. 35: 359–373.

    Article  Google Scholar 

  • Hilmer, T., M. M. B. Talbot & G. C. Bate, 1988. A synthesis of recent botanical research in the Swartkops estuary. In D. Baird, J. F. K. Marais & A. P. Martin (eds), SANCOR Report No. 156, C.S.I.R.: 25–40.

  • Hopkinson, C. S., J. G. Gosselnik & R. T. Parrondo, 1978. Above ground production of seven marsh plant species in coastal Louisiana. Ecology 59: 760–769.

    Article  Google Scholar 

  • Huizinga, P., 1985. A dynamic one-dimensional water quality model. CSIR Res. Rep. 562: 1–23.

    Google Scholar 

  • Kokkinn, M. J. & B. R. Allanson, 1985. On the flux of organic carbon in a tidal salt marsh, Kowie River estuary, Port Alfred, South Africa. S. Afr. J. Sci. 81: 613–617.

    CAS  Google Scholar 

  • Mosterd, S. A., 1983a. Photochemical procedure used in South Africa for the photometric determination of dissolved carbon in seawater. S. Afr. J. mar. Sci. 1: 57–60.

    Article  Google Scholar 

  • Mosterd, S. A., 1983b. Procedure used in South Africa for the automatic photometric determination of micronutrients in seawater. S. Afr. J. mar. Sci. 1: 189–198.

    Article  Google Scholar 

  • Nixon, S. W., 1980. Between coastal marshes and coastal waters: a review of twenty years of speculation and research on the role of saltmarshes in estuarine productivity and water chemistry. In P. Hamilton & K. B. MacDonald (eds), Estuariee and Wetland Processes, with Emphasis on Modelling. Plenum Press, New York: 437–525.

    Chapter  Google Scholar 

  • Odum, E. P., 1980. The status of three ecosystem-level hypotheses regarding salt marsh estuaries: tidal subsidy, outwelling, and detritus-based food chains. In V. S. Kennedy (ed.), Estuarree Perspectives. Academic Press, New York: 485–495.

    Chapter  Google Scholar 

  • Odum, W. E., J. S. Fisher & J. C. Pickral, 1979. Factors controlling the flux of particulate organic carbon from estuarine wetlands. In R. J. Livingston (ed.), Ecological Processes in Coastal and Marine Systems. Plenum Press, New York: 69–80.

    Chapter  Google Scholar 

  • Ott, J., 1988. Meereskunde. Ulmer (UTB), Stuttgart: 386 pp.

    Google Scholar 

  • Pakulski, J. D., 1986. The release of reducing sugars and dissolved organic carbon from Spartina alterniflora Loisel in a Georgia salt marsh. Est. Coast. Shelf Sci. 22: 385–394.

    Article  CAS  Google Scholar 

  • Pierce, S. M., 1979. The contribution of Spartina maritima (Curtis) Fernald to the primary production of the Swartkops estuary. M.Sc.thesis, University of Port Elizabeth.

  • Pomeroy, L. R., K. Bancroft, J. Breed, R. R. Christian, D. Frankenberg, J. R. Hall, L. G. Maurer, W. J. Wiebe, R. G. Wiegert, R. L. Wetzel, 1976. Flux of organic matter through a salt marsh. In M. Wiley (ed.), Estuariee Processes, Vol. 2. Academic Press, New York: 270–279.

    Google Scholar 

  • Teal, J. M., 1962. Energy flow in the salt marsh ecosystem of Georgia. Ecology 43: 614–623.

    Article  Google Scholar 

  • Winter, P. E. D. & D. Baird, 1988. Diversity, productivity and ecological importance of macrobenthic invertebrates in selected eastern cape estuaries. In M. N. Bruton & F. W. Gess (eds), Towards an Environmental Plan for the Eastern Cape. Rhodes University, Grahamstown: 149–154.

    Google Scholar 

  • Wolaver, T. G., S. Hutchinson & M. Marozas, 1986. Dissolved and particulate organic carbon in the North Inlet estuary, South Carolina: What controls their concentrations? Estuaries 9: 31–38.

    Article  CAS  Google Scholar 

  • Wolaver, T. G. & J. D. Spurrier, 1988. Carbon transport between a euhaline vegetated marsh in South Carolina and the adjacent tidal creek: contributions via tidal inundation, runoff and seepage. Mar. Ecol. Prog. Ser. 42: 53–62.

    Article  Google Scholar 

  • Woodwell, G. M. & D. E. Whitney, 1977. Flax Pond ecosystem study: exchanges of phosphorus between a salt marsh and the coastal waters of Long Island Sound. Mar. Biol. 41: 1–6.

    Article  CAS  Google Scholar 

  • Woodwell, G. M., D. E. Whitney, C. A. S. Hall & R. A. Houghton, 1977. The Flax Pond ecosystem study: exchanges of carbon in water between a salt marsh and Long Island Sound. Limnol. Oceanogr. 22: 833–838.

    Article  CAS  Google Scholar 

  • Yelverton, G. F. & C. T. Hackney, 1986. Flux of dissolved organic carbon and pore water through the substrate of a Spartina alterniflora marsh in North Carolina. Est. Coast. Shelf Sci. 22: 255–267.

    Article  CAS  Google Scholar 

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Winter, P.E.D., Schlacherl, T.A. & Baird, D. Carbon flux between an estuary and the ocean: a case for outwelling. Hydrobiologia 337, 123–132 (1996). https://doi.org/10.1007/BF00028513

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  • DOI: https://doi.org/10.1007/BF00028513

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