title: Continental-Scale Increase in Lake and Stream Phosphorus: Are Oligotrophic Systems Disappearing in the United States?
abstract: We describe continental-scale increases in lake and stream total phosphorus (TP) concentrations, identified through periodic probability surveys of thousands of water bodies in the conterminous U.S. The increases, observed over the period 2000-2014 were most notable in sites in relatively undisturbed catchments and where TP was initially low (e.g., less than 10 μg L(-1)). Nationally, the percentage of stream length in the U.S. with TP ≤ 10 μg L(-1) decreased from 24.5 to 10.4 to 1.6% from 2004 to 2009 to 2014; the percentage of lakes with TP ≤ 10 μg L(-1) decreased from 24.9 to 6.7% between 2007 and 2012. Increasing TP concentrations appear to be ubiquitous, but their presence in undeveloped catchments suggests that they cannot be entirely attributed to either point or common non-point sources of TP.
authors.affiliation: United States Environmental Protection Agency , 200 Southwest 35th Street, Corvallis, Oregon 97333, United States.
authors.forename: John L
authors.initials: JL
authors.lastname: Stoddard
authors.affiliation: United States Environmental Protection Agency , 200 Southwest 35th Street, Corvallis, Oregon 97333, United States.
authors.forename: John
authors.initials: J
authors.lastname: Van Sickle
authors.affiliation: Department of Fish and Wildlife, Oregon State University , Corvallis, Oregon 97331, United States.
authors.forename: Alan T
authors.initials: AT
authors.lastname: Herlihy
authors.affiliation: Department of Earth and Environmental Science, University of British Columbia , Kelowna, British Columbia V1V 1V7, Canada.
authors.forename: Janice
authors.initials: J
authors.lastname: Brahney
authors.affiliation: United States Environmental Protection Agency , 200 Southwest 35th Street, Corvallis, Oregon 97333, United States.
authors.forename: Steven
authors.initials: S
authors.lastname: Paulsen
authors.affiliation: United States Environmental Protection Agency , 200 Southwest 35th Street, Corvallis, Oregon 97333, United States.
authors.forename: David V
authors.initials: DV
authors.lastname: Peck
authors.affiliation: Office of Water, United States Environmental Protection Agency , Washington, D.C. 20460, United States.
authors.forename: Richard
authors.initials: R
authors.lastname: Mitchell
authors.affiliation: Office of Water, United States Environmental Protection Agency , Washington, D.C. 20460, United States.
authors.forename: Amina I
authors.initials: AI
authors.lastname: Pollard
mesh_terms: D004784:Environmental Monitoring / Q000379:methods; D060106:Lakes / Q000032:analysis / Q000737:chemistry; D010758:Phosphorus / Q000032:analysis*; D045483:Rivers / Q000737:chemistry; D014481:United States
chemical_list: D010758:Phosphorus