Agriculture causes nitrate fertilization of remote alpine lakes

Authors

Elizabeth J. Hundey, Western UniversityFollow
Sam S.D. Russell, Western UniversityFollow
Fred Longstaffe, Western UniversityFollow
Katrina A. Moser, Western UniversityFollow

Document Type

Article

Publication Date

2-2016

Volume

7

Journal

Nature Communications

First Page

1

URL with Digital Object Identifier

http://dx.doi.org/10.1038/ncomms10571

Last Page

9

Abstract

Humans have altered Earth’s nitrogen cycle so dramatically that reactive nitrogen (Nr) has doubled. This has increased Nr in aquatic ecosystems, which can lead to reduced water quality and ecosystem health. Apportioning sources of Nr to specific ecosystems, however, continues to be challenging, despite this knowledge being critical for mitigation and protection of water resources. Here we use D¹⁷O, d¹⁸O and d¹⁵N from Uinta Mountain (Utah, USA) snow, inflow and lake nitrate in combination with a Bayesian-based stable isotope mixing model, to show that at least 70% of nitrates in aquatic systems are anthropogenic and arrive via the atmosphere. Moreover, agricultural activities, specifically nitrate- and ammonium-based fertilizer use, are contributing most (B60%) Nr, and data from other North American alpine lakes suggest this is a widespread phenomenon. Our findings offer a pathway towards more effective mitigation, but point to challenges in balancing food production with protection of important water resources.