CONTINENTAL-SCALE INCREASE IN LAKE AND STREAM PHOSPHORUS: ARE OLIGOTROPHIC SYSTEMS DISAPPEARING IN THE U.S.?

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1 CONTINENTAL-SCALE INCREASE IN LAKE AND STREAM PHOSPHORUS: ARE OLIGOTROPHIC SYSTEMS DISAPPEARING IN THE U.S.? John L. Stoddard, John van Sickle, Alan T. Herlihy, Janice Brahney, Steven G. Paulsen, David V. Peck, Richard Mitchell, Amina Pollard, Jana E. Compton, Phil Kaufmann December 5, 2017 Stoddard, J. L., J. Van Sickle, A. T. Herlihy, J. Brahney, S. Paulsen, D. V. Peck, R. Mitchell, and A. I. Pollard Continental-Scale Increase in Lake and Stream Phosphorus: Are Oligotrophic Systems Disappearing in the United States? Environmental Science & Technology 50:

2 TOTAL PHOSPHORUS IN STREAM SURVEYS WSA (2004) median = 26 µg/l

3 TOTAL PHOSPHORUS IN STREAM SURVEYS WSA (2004) median = 26 µg/l NRSA (2009) median = 48 µg/l

4 TOTAL PHOSPHORUS IN STREAM SURVEYS WSA (2004) median = 26 µg/l NRSA (2009) median = 48 µg/l NRSA (2014) median = 56 µg/l

5 TOTAL PHOSPHORUS IN LAKE SURVEYS NLA (2007) median = 20 µg/l

6 TOTAL PHOSPHORUS IN LAKE SURVEYS NLA (2007) median = 20 µg/l NLA (2012) median = 37 µg/l

7 OLIGOTROPHIC SYSTEMS POPULATION ESTIMATES

8 TOTAL PHOSPHORUS IN AQUATIC SURVEYS Streams Lakes Peaked Mountain Pond, Maine Table Rock Reservoir, South Carolina Fremont Lake, Wyoming

9 CREATION OF REFERENCE SITE DATASET Least-Disturbed catchments from each survey: < 5% agricultural land use < 1.5% urban land use < 2 km km -2 road density riparian disturbance index values < 1.25 Focused analysis on re-surveyed (overlap) sites located in catchments that pass all of these criteria

10 REFERENCE SITE COMPARISONS Median change ( ) = Median change ( ) = Median change ( ) = +1.5 µg L -1 yr µg L -1 yr µg L -1 yr -1 For All Sites: Median change ( ) = +1.5 µg L -1 yr -1 For All Sites: Median change ( ) = +2.8 µg L -1 yr -1 For All Sites: Median change ( ) = +2.0 µg L -1 yr -1

11 SUPPORTING DATA FROM STATE MONITORING State of Virginia: Proportion of stream length with TP < 10 µg/l (from Larry Willis, Virginia DEQ)

12 WHY? Quality Assurance Problem Migratory birds Forest dieback Insect outbreaks Radionuclide deposition (Fukushima) Forest Fires Global warming Increased incidence of freeze/thaw or wet/dry events Recovery from acidic deposition (Kopáček et al. 2015) Changes in hydrology Changes in Nitrogen Deposition (Musolff et al. 2017) Increased Atmospheric Deposition of Phosphorus (Brahney et al. 2014, 2015)

13 POTENTIAL MECHANISMS Results of Blind Audit Analyses,

14 WHY? Quality Assurance Problem Migratory birds Forest dieback Insect outbreaks Radionuclide deposition (Fukushima) Forest Fires Global warming Increased incidence of freeze/thaw or wet/dry events Recovery from acidic deposition (Kopáček et al. 2015) Changes in hydrology Changes in Nitrogen Deposition (Musolff et al. 2017) Increased Atmospheric Deposition of Phosphorus (Brahney et al. 2014, 2015)

15 ATMOSPHERIC DEPOSITION OF PHOSPHORUS National Atmospheric Deposition Program/National Trends Network NADP/NTN ca. 200 NADP/NTN sites have measurements of orthophosphate for the relevant time period (2000- present) Some technical difficulties with using these results: NADP measures Soluble Reactive Phosphorus In samples that might sit (unfiltered/unpreserved/ unrefrigerated) for up to a week 100,000 individual observations, of which 95,000 are below detection So... data analysis needs to proceed with caution, and with statistics that allow for very censored data

16 ATMOSPHERIC DEPOSITION OF PHOSPHORUS Non-parametric trends in NADP Phosphorus data (200 sites, ) Count All Sites Trends with p < % of sites had upward slopes 67% of sites had trends with p<0.10 (all positive) Median trend = +3.1 µg/l/yr Annual Slope (µg/l/yr)

17 PHOSPHORUS DEPOSITION IN DUST?

18 LOW VISIBILITY AS AN INDIRECT INDICATOR OF DUST STORMS Visibility measured at National Weather Stations across the U.S. low visibility events defined as: visibility change from >6000m to <3000m) no more than one event in a day humidity for a given period of time surrounding the event must be below 80% Assumption is that low visibility events in the absence of rain, mist or fog are due to dust entrained in the air. Visibility Monitor, Canyonlands National Park, Utah Data analysis being conducted by J. Brahney, Utah State University. Methodology explained in: Brahney, J., et al. (2013). "Increasing Ca 2+ deposition in the western US: The role of mineral aerosols." Aeolian Research 10:

19 UNDEVELOPED SITES ONLY

20 Low Visibility Events

21 Low Visibility Events "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." Sherlock Holmes (Arthur Conan Doyle)

22 QUESTIONS? Phoenix, Arizona, July 2012 Phoenix, Arizona, July 2012