, Volume 79, Issue 1–2, pp 109–133 | Cite as

Urban influences on the nitrogen cycle in Puerto Rico

  • Jorge R. Ortiz-Zayas
  • Elvira Cuevas
  • Olga L. Mayol-Bracero
  • Loreto Donoso
  • Ivonne Trebs
  • Debora Figueroa-Nieves
  • William H. McDowell


Anthropogenic actions are altering fluxes of nitrogen (N) in the biosphere at unprecedented rates. Efforts to study these impacts have concentrated in the Northern hemisphere, where experimental data are available. In tropical developing countries, however, experimental studies are lacking. This paper summarizes available data and assesses the impacts of human activities on N fluxes in Puerto Rico, a densely populated Caribbean island that has experienced drastic landscape transformations over the last century associated with rapid socioeconomic changes. N yield calculations conducted in several watersheds of different anthropogenic influences revealed that disturbed watersheds export more N per unit area than undisturbed forested watersheds. Export of N from urban watersheds ranged from 4.8 kg ha−1 year−1 in the Río Bayamón watershed to 32.9 kg ha−1 year−1 in the highly urbanized Río Piedras watershed and 33.3 kg ha−1 year−1 in the rural-agricultural Río Grande de Añasco watershed. Along with land use, mean annual runoff explained most of the variance in fluvial N yield. Wastewater generated in the San Juan Metropolitan Area receives primary treatment before it is discharged into the Atlantic Ocean. These discharges are N-rich and export large amounts of N to the ocean at a rate of about 140 kg ha−1 year−1. Data on wet deposition of inorganic N (\(\hbox{NH}_{4}^{+}+\hbox{NO}_{3}^{-}\)) suggest that rates of atmospheric N deposition are increasing in the pristine forests of Puerto Rico. Stationary and mobile sources of NO x (NO+NO2) and N2O generated in the large urban centers may be responsible for this trend. Comprehensive measurements are required in Puerto Rico to quantitatively characterize the local N cycle. More research is required to assess rates of atmospheric N deposition, N fixation in natural and human-dominated landscapes, N-balance associated with food and feed trade, and denitrification.


Nitrogen Peurto Rico Urbanization Land use change Waste water disposal Atmospheric nitrogen deposition Caribbean Water quality Air quality 


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The authors are grateful to L Martinelli and B Howarth of the Interamerican Nitrogen Network for establishing a very productive forum for discussions and for providing helpful guidance and motivation. Funding for this project was provided by the CREST Center for Applied Tropical Ecology and Conservation of the University of Puerto Rico. D Sotomayor (UPR-Mayaguez) and an anonymous reviewer provided valuable comments that improved the article. The US Geological Survey provided access to water quality and streamflow data. J Coliño of the Puerto Rico Aqueduct and Sewer Authority and M del Valle (CSA Group) provided operational data for the wastewater treatment plants. J Bauza (CSA Group) shared valuable information on coastal N dynamics. A Morales (Puerto Rico Environmental Quality Board) assisted us with air chemistry data. This research is associated to the NSF-funded Luquillo LTER Program.


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Copyright information

© Springer Science+Business Media, Inc. 2006

Authors and Affiliations

  • Jorge R. Ortiz-Zayas
    • 1
  • Elvira Cuevas
    • 2
  • Olga L. Mayol-Bracero
    • 1
  • Loreto Donoso
    • 3
  • Ivonne Trebs
    • 4
  • Debora Figueroa-Nieves
    • 5
  • William H. McDowell
    • 5
  1. 1.Institute for Tropical Ecosystem StudiesSan JuanPuerto Rico
  2. 2.Department of BiologyUniversity of Puerto RicoSan JuanPuerto Rico
  3. 3.Instituto Venezolano de Investigaciones Científicas (IVIC)CaracasVenezuela
  4. 4.Max Planck Institute for ChemistryMainzGermany
  5. 5.University of New HampshireDurhamUSA

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