Subscriber access provided by Purdue University Libraries
Article
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, Steve Paulsen, David V. Peck, Richard Mitchell, and Amina I Pollard Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.5b05950 • Publication Date (Web): 25 Feb 2016 Downloaded from http://pubs.acs.org on February 25, 2016
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 20
Environmental Science & Technology Environmental Science & Technology
1
Continental-scale increase in lake and stream phosphorus: Are
2
oligotrophic systems disappearing in the U.S.?
3
4
Authors: John L. Stoddard1*, John Van Sickle1,2, Alan T. Herlihy3, Janice Brahney4, Steven
5
Paulsen1, David V. Peck1, Richard Mitchell5, Amina I. Pollard5
6
7
8 9
10
11
12
13
14
15
Affiliations: *
(corresponding author): U.S. Environmental Protection Agency, 200 SW 35th Street, Corvallis,
OR, 97333; (541) 754-4441; fax (541)754-4716; [email protected] 1
U.S. Environmental Protection Agency, 200 SW 35th Street, Corvallis, OR, 97333.
2
retired.
3
Oregon State University, Dept. Fish and Wildlife, Corvallis, OR 97331.
4
University of British Columbia, Dept. Earth and Environmental Science, Kelowna, BC, Canada.
5
U.S. Environmental Protection Agency, Office of Water, Washington, DC.
*Correspondence to: [email protected].
16
17
ACS Paragon Plus Environment
Page 2
Environmental Science & Technology Environmental Science & Technology
18
Abstract: We describe continental scale increases in lake and stream total phosphorus (TP)
19
concentrations, identified through periodic probability surveys of thousands of water bodies in
20
the conterminous U.S. The increases, observed over the period 2000-2014, were most notable in
21
sites in relatively undisturbed catchments, and where TP was initially low (e.g., less than 10 µg
22
L-1). Nationally, the percentage of stream length in the U.S. with TP ≤ 10 µg L-1 decreased from
23
24.5 to 10.4 to 1.6% from 2004 to 2009 to 2014; the percentage of lakes with TP ≤ 10 µg L-1
24
decreased from 24.9 to 6.7% between 2007 and 2012. Increasing TP concentrations appear to be
25
ubiquitous, but their presence in undeveloped catchments suggests that they cannot be entirely
26
attributed to either point or common non-point sources of TP.
27
28
1.0 Introduction
29
Phosphorus (P) is a critical nutrient that limits the productivity of many temperate freshwater
30
ecosystems1, 2. Extensive research in the late 1950s to the 1970s revealed how anthropogenic
31
sources of P, especially from industrial and municipal wastewater, facilitated the eutrophication
32
of lakes and streams. Measures have since been implemented to control the supply of P from
33
these point sources, but eutrophication attributable to non-point sources of P (e.g., agricultural,
34
stormwater and wastewater runoff) continues to be widespread3. Recent sizable and
35
economically critical blooms of harmful algae4 have been attributed to these non-point sources.
36
Because of its critical role in aquatic ecosystems, total phosphorus (TP) has been one of the
37
key variables included in the U.S. EPA’s national program of aquatic resources surveys. In this
38
paper we present stream and lake data collected in periodic national surveys conducted
39
cooperatively by the U.S. EPA and the States/Tribes and initiated in 2000. Results from these
ACS Paragon Plus Environment
Page 2 of 20
Page 3 of 20 Page 3
Environmental Science & Technology Environmental Science & Technology
40
randomized, unequal probability surveys provide unbiased estimates of a range of biological,
41
chemical and physical variables at a continental scale, and allow the users to determine the
42
percentage of all lakes and streams that exceeds specific levels of these variables. The data
43
provide a powerful source of information for examining the conditions of water resources and
44
their stressors, across geopolitical, ecological and hydrologic boundaries.
45
2.0 Materials and Methods
46
2.1 Survey Design
47
All of the national surveys described in this paper are randomized, unequally weighted
48
probability surveys5 overseen by the U.S. EPA’s Office of Water
49
(http://www.epa.gov/nheerl/arm/designpages/monitdesign/survey_overview.htm) with the goal
50
of creating unbiased assessments of aquatic resources across the 48 conterminous states. Details
51
of the stream6 and lake7 survey designs have been published elsewhere.
52
The first of these surveys sampled wadeable (1st through 4th Strahler Order) streams in the
53
conterminous U.S. between 2000 and 20048, 9. Additional stream and river surveys have been
54
repeated on a 5 year schedule, with results from the 2008-2009 and 2013-2014 efforts available
55
for the current investigation. A national lake survey was conducted in 2007 and repeated in
56
201210. Each site in each survey was sampled once during a summer index period. In the second
57
and third stream surveys, and the second lake survey, approximately half of the sampled sites
58
were a random subsample of sites also sampled in the previous survey. Details on sample sizes in
59
each survey, and the numbers of resurveyed sites, are shown in Table S1.
ACS Paragon Plus Environment
Page 4
Environmental Science & Technology Environmental Science & Technology
60
The surveys use standardized sampling methods that did not change over our reported time
61
period. At each stream site, a 4-L grab sample was collected from an area of flowing water at or
62
near the designated geographic coordinates assigned to the site as part of the survey design 11 At
63
each lake site, a 4-L integrated water sample was collected from a point on the lake that
64
represented the deepest point of natural lakes or from the mid-point area of reservoirs12. All
65
samples were shipped on ice as soon as possible after collection to an analytical laboratory
66
(overnight courier service was used when necessary and available). Samples typically arrived at
67
a laboratory within 24-48 hours of collection.
68
2.2 Creation of Minimally Disturbed Dataset
69
In order to quantify changes in TP in relatively undisturbed catchments, and to examine
70
potential mechanisms operating in the absence of significant anthropogenic development, we
71
created a minimally-disturbed subset of the resurveyed samples collected as part of each pair of
72
surveys. The contributing watershed area was delineated for each sample site (lake or stream),
73
and percentages of various land use categories calculated for each, using the 2006 National Land
74
Cover Dataset (http://www.mrlc.gov/nlcd2006.php). In addition, the density of roads (km of
75
roads per km2 of catchment) was calculated for each site’s catchment based on the 2006 TIGER
76
database (https://www.census.gov/geo/maps-data/data/tiger.html). Finally, we calculated riparian
77
disturbance at each stream and lake site based on data collected at the time of each survey. In
78
brief, riparian disturbance was estimated from direct observations of 12 specific forms of human
79
riparian disturbance, tallied in either 22 (streams) or 10 (lakes) riparian plots along the stream or
80
lakeshore13, 14. We defined minimally-disturbed15 sites as those with catchments exhibiting
Article
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, Steve Paulsen, David V. Peck, Richard Mitchell, and Amina I Pollard Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.5b05950 • Publication Date (Web): 25 Feb 2016 Downloaded from http://pubs.acs.org on February 25, 2016
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Page 1 of 20
Environmental Science & Technology Environmental Science & Technology
1
Continental-scale increase in lake and stream phosphorus: Are
2
oligotrophic systems disappearing in the U.S.?
3
4
Authors: John L. Stoddard1*, John Van Sickle1,2, Alan T. Herlihy3, Janice Brahney4, Steven
5
Paulsen1, David V. Peck1, Richard Mitchell5, Amina I. Pollard5
6
7
8 9
10
11
12
13
14
15
Affiliations: *
(corresponding author): U.S. Environmental Protection Agency, 200 SW 35th Street, Corvallis,
OR, 97333; (541) 754-4441; fax (541)754-4716; [email protected] 1
U.S. Environmental Protection Agency, 200 SW 35th Street, Corvallis, OR, 97333.
2
retired.
3
Oregon State University, Dept. Fish and Wildlife, Corvallis, OR 97331.
4
University of British Columbia, Dept. Earth and Environmental Science, Kelowna, BC, Canada.
5
U.S. Environmental Protection Agency, Office of Water, Washington, DC.
*Correspondence to: [email protected].
16
17
ACS Paragon Plus Environment
Page 2
Environmental Science & Technology Environmental Science & Technology
18
Abstract: We describe continental scale increases in lake and stream total phosphorus (TP)
19
concentrations, identified through periodic probability surveys of thousands of water bodies in
20
the conterminous U.S. The increases, observed over the period 2000-2014, were most notable in
21
sites in relatively undisturbed catchments, and where TP was initially low (e.g., less than 10 µg
22
L-1). Nationally, the percentage of stream length in the U.S. with TP ≤ 10 µg L-1 decreased from
23
24.5 to 10.4 to 1.6% from 2004 to 2009 to 2014; the percentage of lakes with TP ≤ 10 µg L-1
24
decreased from 24.9 to 6.7% between 2007 and 2012. Increasing TP concentrations appear to be
25
ubiquitous, but their presence in undeveloped catchments suggests that they cannot be entirely
26
attributed to either point or common non-point sources of TP.
27
28
1.0 Introduction
29
Phosphorus (P) is a critical nutrient that limits the productivity of many temperate freshwater
30
ecosystems1, 2. Extensive research in the late 1950s to the 1970s revealed how anthropogenic
31
sources of P, especially from industrial and municipal wastewater, facilitated the eutrophication
32
of lakes and streams. Measures have since been implemented to control the supply of P from
33
these point sources, but eutrophication attributable to non-point sources of P (e.g., agricultural,
34
stormwater and wastewater runoff) continues to be widespread3. Recent sizable and
35
economically critical blooms of harmful algae4 have been attributed to these non-point sources.
36
Because of its critical role in aquatic ecosystems, total phosphorus (TP) has been one of the
37
key variables included in the U.S. EPA’s national program of aquatic resources surveys. In this
38
paper we present stream and lake data collected in periodic national surveys conducted
39
cooperatively by the U.S. EPA and the States/Tribes and initiated in 2000. Results from these
ACS Paragon Plus Environment
Page 2 of 20
Page 3 of 20 Page 3
Environmental Science & Technology Environmental Science & Technology
40
randomized, unequal probability surveys provide unbiased estimates of a range of biological,
41
chemical and physical variables at a continental scale, and allow the users to determine the
42
percentage of all lakes and streams that exceeds specific levels of these variables. The data
43
provide a powerful source of information for examining the conditions of water resources and
44
their stressors, across geopolitical, ecological and hydrologic boundaries.
45
2.0 Materials and Methods
46
2.1 Survey Design
47
All of the national surveys described in this paper are randomized, unequally weighted
48
probability surveys5 overseen by the U.S. EPA’s Office of Water
49
(http://www.epa.gov/nheerl/arm/designpages/monitdesign/survey_overview.htm) with the goal
50
of creating unbiased assessments of aquatic resources across the 48 conterminous states. Details
51
of the stream6 and lake7 survey designs have been published elsewhere.
52
The first of these surveys sampled wadeable (1st through 4th Strahler Order) streams in the
53
conterminous U.S. between 2000 and 20048, 9. Additional stream and river surveys have been
54
repeated on a 5 year schedule, with results from the 2008-2009 and 2013-2014 efforts available
55
for the current investigation. A national lake survey was conducted in 2007 and repeated in
56
201210. Each site in each survey was sampled once during a summer index period. In the second
57
and third stream surveys, and the second lake survey, approximately half of the sampled sites
58
were a random subsample of sites also sampled in the previous survey. Details on sample sizes in
59
each survey, and the numbers of resurveyed sites, are shown in Table S1.
ACS Paragon Plus Environment
Page 4
Environmental Science & Technology Environmental Science & Technology
60
The surveys use standardized sampling methods that did not change over our reported time
61
period. At each stream site, a 4-L grab sample was collected from an area of flowing water at or
62
near the designated geographic coordinates assigned to the site as part of the survey design 11 At
63
each lake site, a 4-L integrated water sample was collected from a point on the lake that
64
represented the deepest point of natural lakes or from the mid-point area of reservoirs12. All
65
samples were shipped on ice as soon as possible after collection to an analytical laboratory
66
(overnight courier service was used when necessary and available). Samples typically arrived at
67
a laboratory within 24-48 hours of collection.
68
2.2 Creation of Minimally Disturbed Dataset
69
In order to quantify changes in TP in relatively undisturbed catchments, and to examine
70
potential mechanisms operating in the absence of significant anthropogenic development, we
71
created a minimally-disturbed subset of the resurveyed samples collected as part of each pair of
72
surveys. The contributing watershed area was delineated for each sample site (lake or stream),
73
and percentages of various land use categories calculated for each, using the 2006 National Land
74
Cover Dataset (http://www.mrlc.gov/nlcd2006.php). In addition, the density of roads (km of
75
roads per km2 of catchment) was calculated for each site’s catchment based on the 2006 TIGER
76
database (https://www.census.gov/geo/maps-data/data/tiger.html). Finally, we calculated riparian
77
disturbance at each stream and lake site based on data collected at the time of each survey. In
78
brief, riparian disturbance was estimated from direct observations of 12 specific forms of human
79
riparian disturbance, tallied in either 22 (streams) or 10 (lakes) riparian plots along the stream or
80
lakeshore13, 14. We defined minimally-disturbed15 sites as those with catchments exhibiting
