Changing nutrients, changing rivers

• Published in: Science (American Association for the Advancement of Science) Vol. 365; no. 6454; pp. 637 - 638
• Main Authors: Ibáñez, Carles, Peñuelas, Josep
• Format: Journal Article
• Language: English
• Published: United States American Association for the Advancement of Science 16.08.2019; The American Association for the Advancement of Science
• Subjects: Aquatic plants; Developed countries; Developed Nations; Ecological conditions; Ecological effects; Ecological monitoring; Environmental changes; Estuaries; Estuarine environments; Eutrophication; Lakes; Macrophytes; Nitrogen; Nutrients; PERSPECTIVES; Phosphorus; Phytoplankton; Rivers; Water quality
• DOI: 10.1126/science.aay2723
• ISSN: 0036-8075; 1095-9203

Phosphorus removal from freshwater systems has wide-ranging ecological consequences Eutrophication—the excessive enrichment of a body of water with nutrients such as nitrogen (N) and phosphorus (P)—is Earth's most widespread problem for water quality ( 1 , 2 ). Growing evidence suggests a global trend toward reversing eutrophication. However, in rivers and estuaries of developed countries and in lakes of emerging economies, the ongoing reduction in nutrient inputs—termed reoligotrophication—is much larger for P than for N ( 3 , 4 ). Although the rapid emergence of this phenomenon has hindered detailed monitoring of the ecological effects, a few studies have documented an abrupt shift from green to clear waters and consequently from phytoplankton to macrophytes as dominant primary producers in response to reoligotrophication in rivers and estuaries ( 5 – 7 ). However, the improvement in water quality due to P decline does not imply a return to pristine ecological conditions, because high N:P ratios trigger undesirable changes in the ecosystem ( 8 ).