Nutrient dynamics

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Nutrient export fluxes in coastal systems, primarily as nitrogen (N), phosphorus (P) and silicon (Si), have a significant impact on water quality and control the nature and magnitude of coastal productivity. In coastal areas, nutrients are delivered by rivers, groundwater discharge and atmospheric deposition. The growing impact of anthropogenic activities has profoundly affected the quality of marine waters over the last 50 years. Such alterations are well documented and have been linked to perturbations in nutrient export fluxes from the continent[1] . In areas of restricted water exchange, the export of excess N and P to coastal waters may cause coastal eutrophication, a blooming of suspended and bed-anchored algae (including toxic species), alteration of community structures, degradation in the ecosystem function and modifications of marine food webs[2] . The continuing changes in land use and global urbanisation of coastal margins[3] thus pose a continual threat to coastal waters.

CONTINENTAL NUTRIENT SOURCES

Rivers

On a global scale, riverine inputs of N and P to coastal seas have possibly increased by factors of 2 to 3 [4] ,[5] ,[6]. Agriculture, in the form of fertilizers, leachates and animal wastes, is the largest contributor of N and P in aquatic systems [4] . Other major inputs include point-source discharges of wastewater from urban sewer networks[7] ,[8] and industrial wastes. The direct discharge of P exchanged with soils and sediments[9] also contributes significantly to the budget of this element.

Riverine Si fluxes, originating
  1. Vanderborght, J-P, I. Folmer, D. Rodriguez Aguilera, T. Uhrenholt, and P. Regnier (2007), Reactive-transport modelling of a river-estuarine coastal zone system: application to the Western Scheldt, Marine Chemistry 106, 92-110.
  2. Garnier, J., G. Billen, E. Hannon, S. Fonbonna, Y. Videnia, and M. Soulie (2002), Modelling the transfer and retention of nutrients in the drainage network of the Danube river, Estuarine, Coastal and Shelf Science, 54, 285-308.
  3. Tappin, A.D. (2002), An Examination of the Fluxes of Nitrogen and Phosphorus in Temperate and Tropical Estuaries: Current Estimates and Uncertainties, Estuarine, Coastal and Shelf Science 55, 885-901.
  4. 4.0 4.1 Howarth, R., H. Jensen, R. Marino, and H. Postma, in Phosphorus in the Global Environment:Transfers, Cycles and Management, H. Tiessen, Ed., Scientific Committee on Problems of the Environment 54. (Wiley, New York, 1995), pp. 323–356.
  5. Duce, R., P.S. Liss, J.T. Merrill, E.L. Atlas, P. Buat-Menard, B.B. Hicks, J.M. Miller, J.M. Prospero, R. Arimoto, T.M. Church,. W. Ellis, J.N. Galloway, L. Hansen, T.D. Jickells, A.H. Knap, K.H. Reinhardt, B. Schneider, A. Soudine, J.J. Tokos, S. Tsunogai, R. Wollast, and M. Zhou (1991), The atmospheric input of trace species to the world ocean, Global Biogeochemical Cycles 5, 193-296.
  6. Jickells T.D. (1998), Nutrient Biogeochemistry of the Coastal Zone, Science, 281 217 – 222
  7. Billen, G., J. Garnier, J. Nemery, M. Sebilo, A. Sferratore, S. Barles, P. Benoit, and M. Benoit (2007), A long-term view of nutrient transfers through the Seine river continuum, Science of the Total Environment 375, 80-97.
  8. European Environment Agency (1999), Nutrients in European Ecosystems. Environmental Assessment Report No. 4, Office for Official Publications of the European Communities, Luxembourg, pp. 156.
  9. Billen, G., C. Lancelot, and M. Meybeck (1991), N, P and Si retention along the aquatic continuum from land to ocean. Ocean Margin Processes in Global Change, R.F.C Mantoura, J.-M. Martin, and R. Wollast, Eds. (John Wiley & Sons Ltd.), pp. 19-44.