Aquatic Sciences Meeting, Albuquerque 2001

SS31 Integrated Approaches to Drainage Basin Nutrient Inputs and Inland/Coastal Eutrophication (Science and Society Connections)

Date: Thursday, February 15, 2001, Time: 10:45:00 AM

Location: Cimarron

Turner, R, E, Louisiana State University, Baton Rouge, LA, USA, euturne@lsu.edu

Rabalais, N, N, LUMCON, Chauvin, LA, USA, nrabalais@lumcon.edu

Justic, D, , Louisiana State University, Baton Rouge, LA, USA, djusti1@lsu.edu

Dortch, Q, , LUMCON, Chuavin, LA, USA, qdortch

Global patterns of dissolved silicate and nitrogen in large rivers

The concentration of dissolved inorganic nitrogen (DIN), nitrate-N, inorganic phosphate (DIP) and silicate (DSi), and their ratios in the world's largest rivers are summarized using a global data base that includes 37 % of the earth's watershed area and half its population. These data were compared to water quality in forty-two sub-basins of the relatively well-monitored Mississippi River basin (MRB). The average total nitrogen concentration varies over 3 orders of magnitude among both world river watersheds and the MRB, and is primarily dependent on variations in dissolved nitrate concentration, rather than particulate or dissolved organic matter or ammonium. When the nitrate-N concentration exceeds 50 µg at l-1, the DIN : DIP ratio is generally above the Redfield ratio (1 : 16), which implies phosphorus limitation of phytoplankton growth. Compared to nitrate, the among river variations in DSi) concentration is relatively small so that the DSi loading is largely controlled by runoff volume. The DSi : nitrate-N ratio is inversely correlated with various indices of landscape development (e.g., population density, agricultural and economic intensity).

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Aquatic Sciences Meeting, Albuquerque 2001

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