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: 3:00:00 PM

Location: Cimarron

Cifuentes, L, A, Texas A&M University, Oceanography Department, College Station, USA, cifuentes@ocean.tamu.edu

Kaldy, J, E, Texas A&M University, Oceanography Department, College Station, USA,

Morse, J, W, Texas A&M University, Oceanography Department, College Station, USA,

SIGNIFICANCE OF UREA AND NITRATE TO AMMONIUM RATIOS FOUND IN DIVERSE AQUATIC ENVIRONMENTS

Compared with other nitrogenous nutrient species, little is known about sources and sinks of urea in aquatic environments. Urea, nitrate and ammonium data was available from diverse environments, including two contaminated groundwater locations, one river, three estuaries, and the Gulf of Mexico continental shelf. Pore water was also recovered from estuarine and shelf sediments. Mean urea concentrations varied from < 1 to about 30 micromolar. Low mean concentrations were found in both groundwater and estuarine water, whereas pore water appeared to accumulate urea. Both averages and standard deviations of urea to ammonium and nitrate to ammonium ratios varied among sites. Oxic environments, where organic nitrogen decomposition to ammonium occurs through an urea intermediate and is followed by ammonium oxidation, had higher urea to ammonium ratios and nitrate to ammonium ratios in contrast with sub-oxic environments where nitrification (and coupled nitrification-denitrification) can not take place. The relevance of these ratios with respect to anthropogenic inputs will also be discussed.

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Aquatic Sciences Meeting, Albuquerque 2001

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