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Marine and Freshwater Research Marine and Freshwater Research Society
Advances in the aquatic sciences
RESEARCH ARTICLE

Nitrogen nutrients in a subtropical river: temporal variation and analysis at different spatial scales

Rodrigo Moncayo-Estrada A D , Carlos Escalera-Gallardo B , Miriam Arroyo-Damián C , Oswaldo Campos-Campos B and José T. Silva-García B
+ Author Affiliations
- Author Affiliations

A Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas, Avenida Instituto Politécnico Nacional s/n, Col. Playa de Santa Rita, COFAA, La Paz, BCS, 23096 México.

B Instituto Politécnico Nacional, Centro Interdisciplinario de Investigación para el Desarrollo Integral Regional, Justo Sierra 28, COFAA, Jiquilpan, Michoacán, 59510 México.

C Universidad de la Ciénega del Estado de Michoacán de Ocampo, Las Higueras 3000, Lomas de Universidad, 59103 Jiquilpan, Michoacán, México.

D Corresponding author. Email: rmoncayo@ipn.mx

Marine and Freshwater Research 68(10) 1935-1949 https://doi.org/10.1071/MF16344
Submitted: 28 January 2016  Accepted: 16 January 2017   Published: 30 March 2017

Abstract

Herein we provide a framework for evaluating the spatiotemporal variation of nitrate and ammonium and their relationships with environmental and anthropogenic variables at different scales. Bimonthly samples were collected from 28 sites in the Duero River, Mexico, from May to December 2013. The river flow changed and lost connectivity during the dry season because more water was diverted for irrigation. Four sites had the highest nitrate and ammonium values (7.6 and 22.1 mg L–1 respectively), which were related to direct waste water discharge. The remaining 24 sites were analysed using a multivariate approach. Using hierarchical cluster analysis, seasonal trends were identified with two groupings during July and five in December. Sites were grouped into those with constant discharge and nitrates affected by springs and those with poor water quality (high concentrations of ammonium). Non-metric multidimensional scaling simultaneously revealed the variation in time and space, organised sites into an environmental ammonium gradient and differentiated between seasons according to nitrate levels. Regression tree analysis established a relationship between nutrients and independent variables. At the landscape level, the agricultural area affected nitrate (75%) and urban area affected ammonium (45%); at the basin level, road density influenced both parameters (10.68 km per 25 km2).

Additional keywords: agricultural watershed, Duero River, multivariate analysis, restoration actions, riverine landscape, waste water input.


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