BGD Biogeosciences Discussions BGD Biogeosciences Discuss. 1810-6285 Göttingen, Germany 10.5194/bgd-6-1091-2009 Contribution of riverine nutrients to the silicon biogeochemistry of the global ocean – a model study Bernard C. Y. 1 Dürr H. H. 2 Heinze C. 1 Segschneider J. 3 Maier-Reimer E. 3 Bjerknes Centre for Climate Research, Geophysical Institute, University of Bergen, Allégaten 70, 5007 Bergen, Norway Department of Physical Geography, Faculty of Geosciences, Utrecht University, The Netherlands Max-Planck-Institute for Meteorology, 20146 Hamburg, Germany 21 01 2009 6 1 1091 1119 Copyright: © 2009 C. Y. Bernard et al. 2009 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://bg.copernicus.org/preprints/6/1091/2009/bgd-6-1091-2009.html The full text article is available as a PDF file from https://bg.copernicus.org/preprints/6/1091/2009/bgd-6-1091-2009.pdf

Continental shelf seas are known to support a large fraction of the global primary production. Yet, continental shelf areas are mostly ignored or neglected in global biogeochemical models. A number of processes that control the transfer of dissolved nutrients from river to the open ocean remain poorly understood. This applies in particular to dissolved silica which drives the growth of diatoms that form a large part of the phytoplankton biomass and are thus an important contributor to export production of carbon. <br><br> Here, the representation of the biogeochemical state along continents is improved by coupling a high resolution database of riverine fluxes of nutrients to the global biogeochemical ocean general circulation model MPI-OM/HAMOCC5. Focusing on silicon (Si), but including the whole suite of nutrients – carbon (C), nitrogen (N) and phosphorus (P) in various forms – inputs are implemented in the model at coastal coupling points using the COSCAT global database of 156 mega-river-ensemble catchments from Meybeck et al. (2006). The catchments connect to the ocean through coastal segments according to three sets of criteria: natural limits, continental shelf topography, and geophysical dynamics. <br><br> According to the model the largest effects on nutrient concentrations occur in hot spots such as the Amazon plume, the Arctic – with high nutrient inputs in relation to its total volume, and areas that encounter the largest increase in human activity, e.g., Southern Asia.

 References Amiotte-Suchet, P. A., Probst, J. L., and Ludwig, W.: Worldwide distribution of continental rock lithology: Implications for the atmospheric/soil CO<sub>2</sub> uptake by continental weathering and alkalinity river transport to the oceans, Global Biogeochem. Cy., 17, 1038, https://doi.org/10.1029/2002GB001189, 2003. Aumont, O., Maier-Reimer, E., Blain, S., and Monfray, P.: An ecosystem model of the global ocean including Fe, Si, P colimitations, Global Biogeochem. Cy., 17, 1060, https://doi.org/10.1029/2001GB001745, 2003. Behrenfeld, M. J., Bale, A. J., Kolber, Z. S., Aiken, J., and Falkowski, P. G.: Confirmation of iron limitation of phytoplankton photosynthesis in the equatorial Pacific Ocean, Nature, 383, 508–511, 1996. Beusen, A. H. W., Dekkers, A. L. M., Bouwman, A. F., Ludwig, W., and Harrison, J.: Estimation of global river transport of sediments and associated particulate C, N, and P, Global Biogeochem. Cy., 19, 2005. Bidle, K. D. and Azam, F.: Accelerated dissolution of diatom silica by marine bacterial assemblages, Nature, 397, 508–512, 1999. Conley, D. J., Schelske, C. L., and Stoermer, E. F.: Modification of the Biogeochemical Cycle of Silica with Eutrophication, Mar. Ecol.-Prog. Ser., 101, 179–192, 1993. Da Cunha, L. C., Buitenhuis, E. T., Le Quere, C., Giraud, X., and Ludwig, W.: Potential impact of changes in river nutrient supply on global ocean biogeochemistry, Global Biogeochem. Cy., 21, 2007. Dugdale, R. C., Wilkerson, F. P., and Minas, H. J.: The Role of a Silicate Pump in Driving New Production, Deep-Sea Research Pt. I-, 42, 697–719, 1995. Dumont, E., Harrison, J. A., Kroeze, C., Bakker, E. J., and Seitzinger, S. P.: Global distribution and sources of dissolved inorganic nitrogen export to the coastal zone: Results from a spatially explicit, global model, Global Biogeochem. Cy., 19, GB4S02, https://doi.org/10.1029/2005GB002488 , 2005. Dürr, H. H., Meybeck, M., Hartmann, J., Laruelle, G. G., and Roubeix, V.: Global spatial distribution of natural river silica inputs to the coastal zone, Biogeosciences Discuss., 6, 1–57, 2009. Egge, J. K. and Aksnes, D. L.: Silicate as Regulating Nutrient in Phytoplankton Competition, Mar. Ecol.-Prog. Ser., 83, 281–289, 1992. Eriksson, H., Pastuszak, M., Lofgren, S., Morth, C. M., and Humborg, C.: Nitrogen budgets of the Polish agriculture 1960–2000: implications for riverine nitrogen loads to the Baltic Sea from transitional countries, Biogeochemistry, 85, 153–168, 2007. Gong, G. C., Chang, J., Chiang, K. P., Hsiung, T. M., Hung, C. C., Duan, S. W., and Codispoti, L. A.: Reduction of primary production and changing of nutrient ratio in the East China Sea: Effect of the Three Gorges Dam?, Geophys. Res. Lett., 33, L07610, https://doi.org/10.1029/2006GL025800, 2006. Graham, W. M.: Numerical increases and distributional shifts of Chrysaora quinquecirrha (Desor) and Aurelia aurita (Linne) (Cnidaria : Scyphozoa) in the northern Gulf of Mexico, Hydrobiologia, 451, 97–111, 2001. Harrison, J. A., Caraco, N., and Seitzinger, S. P.: Global patterns and sources of dissolved organic matter export to the coastal zone: Results from a spatially explicit, global model, Global Biogeochem. Cy., 19, GB4S04, https://doi.org/10.1029/2005GB002480, 2005a. Harrison, J. A., Seitzinger, S. P., Bouwman, A. F., Caraco, N. F., Beusen, A. H. W., and Vorosmarty, C. J.: Dissolved inorganic phosphorus export to the coastal zone: Results from a spatially explicit, global model, Global Biogeochem. Cy., 19, GB4S03, https://doi.org/10.1029/2004GB002357, 2005b. Heinze, C., Maier-Reimer, E., Winguth, A. M. E., and Archer, D.: A global oceanic sediment model for long-term climate studies, Global Biogeochem. Cy., 13, 221–250, 1999. Humborg, C., Conley, D. J., Rahm, L., Wulff, F., Cociasu, A., and Ittekkot, V.: Silicon retention in river basins: Far-reaching effects on biogeochemistry and aquatic food webs in coastal marine environments, Ambio, 29, 45–50, 2000. Hutchins, D. A. and Bruland, K. W.: Iron-limited diatom growth and Si : N uptake ratios in a coastal upwelling regime, Nature, 393, 561–564, 1998. Johnson, H. P., Hautala, S. L., Bjorklund, T. A., and Zarnetske, M. R.: Quantifying the North Pacific silica plume, Geochem. Geophy. Geosy., 7, Q05011, https://doi.org/10.1029/2005GC001065, 2006. Johnson, K. S., Chavez, F. P., and Friederich, G. E.: Continental-shelf sediment as a primary source of iron for coastal phytoplankton, Nature, 398, 697–700, 1999. Justic, D., Rabalais, N. N., and Turner, R. E.: Stoichiometric nutrient balance and origin of coastal eutrophication, Mar. Pollut. Bull., 30, 41–46, 1995a. Justic, D., Rabalais, N. N., Turner, R. E., and Dortch, Q.: Changes in nutrient structure of river-dominated coastal waters : stoichiometric nutrient balance and its consequences, Estuar. Coast. Shelf S., 40, 339–356, 1995b. Kroeze, C. and Seitzinger, S. P.: Nitrogen inputs to rivers, estuaries and continental shelves and related nitrous oxide emissions in 1990 and 2050: a global model, Nutr. Cycl. Agroecosys., 52, 195–212, 1998. Mahowald, N. M., Muhs, D. R., Levis, S., Rasch, P. J., Yoshioka, M., Zender, C. S., and Luo, C.: Change in atmospheric mineral aerosols in response to climate: Last glacial period, preindustrial, modern, and doubled carbon dioxide climates, J. Geophys. Res.-Atmos., 111, D10202, https://doi.org/10.1029/2005JD006653, 2006. Maier-Reimer, E.: Geochemical cycles in an ocean general circulation model. Preindustrial tracer distributions, Global Biogeochem. Cy., 7, 645–677, 1993. Maier-Reimer, E., Kriest, I., Segschneider, J., and Wetzel, P.: Technical description of the HAMburg Ocean Carbon Cycle model, version~5.1 (HAMOCC5.1), and of its interface to MPI-OM, online: http://www.mpimet.mpg.de/wissenschaft/modelle/mpiom/mpiom-description.html, last access: 2008, 2005. Marsland, S. J., Haak, H., Jungclaus, J. H., Latif, M., and Roske, F.: The Max-Planck-Institute global ocean/sea ice model with orthogonal curvilinear coordinates, Ocean Model., 5, 91–127, 2003. McGinnis, D. F., Bocaniov, S., Teodoru, C., Friedl, G., Lorke, A., and Wuest, A.: Silica retention in the Iron Gate I reservoir on the Danube River: The role of side bays as nutrient, River Res. Appl., 22, 441–456, 2006. Meybeck, M., Durr, H. H., and Vorosmarty, C. J.: Global coastal segmentation and its river catchment contributors: A new look at land-ocean linkage, Global Biogeochem. Cy., 20, 2006. Nikiema, O., Devenon, J. L., and Baklouti, M.: Numerical modeling of the Amazon River plume, Cont. Shelf Res., 27, 873–899, 2007. Poulton, S. W. and Raiswell, R.: The low-temperature geochemical cycle of iron: From continental fluxes to marine sediment deposition, Am. J. Sci., 302, 774–805, 2002. Purcell, J. E., Malej, A., and Benovic, A.: Potential links of jellyfish to eutrophication and fisheries, in: Ecosystems at the land-sea margin: drainage basin to coastal sea, edited by: Malone, T. C., Malej, A., Harding Jr., L. W., Smodlaka, N. and Turner, R. E., Coastal and Estuarine Studies, 55, 241–263, 1999. Rabalais, N. N., Wiseman, W. J., Turner, R. E., SenGupta, B. K., and Dortch, Q.: Nutrient changes in the Mississippi River and system responses on the adjacent continental shelf, Estuaries, 19, 386–407, 1996. Rabouille, C., Mackenzie, F. T., and Ver, L. M.: Influence of the human perturbation on carbon, nitrogen, and oxygen biogeochemical cycles in the global coastal ocean, Geochim. Cosmochim. Ac., 65, 3615–3641, 2001. Ragueneau, O., Chauvaud, L., Leynaert, A., Thouzeau, G., Paulet, Y. M., Bonnet, S., Lorrain, A., Grall, J., and Corvaisier, R.: Direct evidence of a biologically active coastal silicate pump: Ecological implications, Limnol. Oceanogr., 47, 1849–1854, 2002. Seitzinger, S. P., Harrison, J. A., Dumont, E., Beusen, A. H. W., and Bouwman, A. F.: Sources and delivery of carbon, nitrogen, and phosphorus to the coastal zone: An overview of Global Nutrient Export from Watersheds (NEWS) models and their application, Global Biogeochem. Cy., 19, GB4S01, https://doi.org/10.1029/2005GB002606, 2005. Six, K. D. and MaierReimer, E.: Effects of plankton dynamics on seasonal carbon fluxes in an ocean general circulation model, Global Biogeochem. Cy., 10, 559–583, 1996. Treguer, P., Nelson, D. M., Vanbennekom, A. J., Demaster, D. J., Leynaert, A., and Queguiner, B.: The Silica Balance in the World Ocean – a Reestimate, Science, 268, 375–379, 1995. Ver, L. M. B., Mackenzie, F. T., and Lerman, A.: Carbon cycle in the coastal zone: effects of global perturbations and change in the past three centuries, Chem. Geol., 159, 283–304, 1999. Vorosmarty, C. J., Fekete, B. M., Meybeck, M., and Lammers, R. B.: Global system of rivers: Its role in organizing continental land mass and defining land-to-ocean linkages, Global Biogeochem. Cy., 14, 599–621, 2000a. Vorosmarty, C. J., Fekete, B. M., Meybeck, M., and Lammers, R. B.: Geomorphometric attributes of the global system of rivers at 30-minute spatial resolution, J. Hydrol., 237, 17–39, 2000b. Wells, M. L. and Mayer, L. M.: Variations in the Chemical Lability of Iron in Estuarine, Coastal and Shelf Waters and Its Implications for Phytoplankton, Mar. Chem., 32, 195–210, 1991. Wells, M. L. and Trick, C. G.: Controlling iron availability to phytoplankton in iron-replete coastal waters, Mar. Chem., 86, 1–13, https://doi.org/10.1016/j.marchern.2003.10.003, 2004. Wetzel, P.: Interannual and Decadal Variability in the Air-Sea Exchange of CO<sub>2</sub> – a Model Study, Ph.D. thesis, p 127, 2004. Wetzel, P., Winguth, A., and Maier-Reimer, E.: Sea-to-air CO<sub>2</sub> flux from 1948 to 2003: A model study, Global Biogeochem. Cy., 19, GB2005, https://doi.org/10.1029/2004GB002339, 2005.