satellite remote sensing of chlorophyll a in support of
TRANSCRIPT
Satellite Remote Sensing of Chlorophyll a in Support of Nutrient Management in the Neuse and Tar-
Pamlico River estuaries
Darryl J. Keith, Research Oceanographer EPA/ORD/NHEERL/Atlantic Ecology Division
Monitor Track Berne Room 11:30am – noon
Introduction The North Carolina Environmental Management Commission (EMC)
has adopted as a water quality standard that chlorophyll a concentration should not exceed 40 μg/L in sounds, estuaries and other slow-moving waters.
Exceedances require the development of a Total Maximum Daily Limit (TMDL) for nutrients in that water body.
Chlorophyll a was chosen as the endpoint to manage total nitrogen concentrations in the Phase I TMDL for the Neuse River
TMDL compliance would be achieved if Chl a exceedances occurred in fewer than 10% of the samples collected in a specified area and time
(aka “10/40 criterion” or “Neuse Rules”)
Questions What is the relationship between chlorophyll a and total nitrogen
(TN) in east coast estuaries and the Neuse River estuary in particular?
Can the amount of estuarine acres impaired by chlorophyll a be determined using the high spatial capability of MERIS derived data?
Can TMDL compliance and chlorophyll exceedances in the Neuse and Tar-Pamlico River estuaries be assessed at daily and annual time scales from MERIS imagery?
Which summary statistic of chlorophyll a concentrations (sample mean, median, and 90th percentile values) is the most useful for determining TMDL violations and to support environmental compliance monitoring?
Methods
Conducted linear regression analysis of TN concentrations and Chl a
values from Mid-Atlantic (including the Neuse River estuary) and New England estuaries.
*Datasets were collected by the USEPA Mid Atlantic Integrated Assessment
(MAIA-1998) and National Coastal Assessment (NCA) Programs (2000 - 2004) as well as the Lower Neuse Basin Association (LNBA-1995 and 1998)
• Used the MERIS Chl a product derived from atmospherically-corrected, full resolution (300 X 300 m pixel size) images (n= 206) of the Neuse and Tar-Pamlico River estuaries to determine the number of pixels exceeding 40 μg/L from January 2006 to December 2009.
* MERIS images were acquired from the European Space Agency (ESA) by Ross Lunetta of the EPA National Exposure Research Laboratory (NERL) Landscape Characterization Branch (LCB) in 2009 to create the Albemarle-Pamlico Basin Change Detection Viewer website (http://maps6.epa.gov/aptw/viewer.htm).
Methods
Used Type I linear regression to develop a semi-empirical model to predict Chl a concentrations (Chl a ambient) calibrated for the Neuse and Tar-Pamlico River estuaries from MERIS chlorophyll values using in situ Chl a data from FerryMon and the NCDENR Ambient Monitoring System (AMS).
* The accuracy of the correction algorithm was assessed by calculating the goodness-of-fit (R²) of measured vs. predicted values
*Error was assessed from Root Mean Square Error (RMSE) of the corrected Chl a concentrations from:
RMSE (μg/L)=√((∑(Chl a measured)-Chl a predicted)2)/(N-1) where N = number of samples
Methods Daily compliance of the 10/40 criterion for the Neuse and Tar-
Pamlico estuaries was evaluated by summing the number of pixels with chl a concentrations ≥40 ug/L and dividing by the total number of pixels in an image to get a percentage.
The percentage was then used to determine if violations of the 10/40 criterion had occurred on a daily image.
Annual compliance was evaluated by aggregating all pixels that violated the 10/40 criterion for a given year and dividing by the total number of pixels for all MERIS images during that period.
The percentage of pixels >40 ug/L was used to determine TMDL status for the year
Did fewer than 10% of the samples collected in an estuary in a day exceed 40 ug/L?
Did fewer than 10% of the samples collected in an estuary in a year exceed 40 ug/L?
Methods
The arithmetic mean, median (50th percentile), and 90th percentile concentrations of Chl aambient for each image were calculated using statistical routines found in the Data Analysis tool package of EXCEL 2007 and plotted against time.
9
What is ocean/estuary color?
Rrs(0+,λ) = Lw (0
+,λ)/ Es(0+,λ)
Rrs = remotely sensed reflectance (1/sr)
Lw (λ) = water leaving radiance measured above the air/water interface (W m-2 sr-1),
Es (λ) = downwelling irradiance measured above the air/water interface (W m-2 sr-1)
Definition of Remotely Sensed Reflectance (Rrs)
Remotely sensed reflectance
Remotely sensed reflectance
Optical components and pathways of radiance and reflectance in coastal waters
Multiple light paths • Scattering due to:
– atmosphere – aerosols – water surface – suspended particles – bottom
• Absorption due to: – atmosphere – aerosols – suspended particles – dissolved matter
Interrelationship between optical properties and in-water constituents
Composite RSR Spectra-
Narragansett Bay Stations
0
0.002
0.004
0.006
0.008
0.01
0.012
350 450 550 650 750
Wavelength (nm)
Rem
ote
Sen
sin
g R
efl
ecta
nce (1
/sr) PRUAQUI
PRUJAM
BRIHAR
12
POTCOV
GRENBAY
36
4
40
7
For example:
[Chl a] [TSS] CDOM salinity
Empirical models
SENSOR
(spatial resolution)
PLATFORM
AGENCY
Data Distribution
Policy Data Access Cost to User
HICO
100 m
International
Space Station
(Sept 2009 –present)
NASA
ISS
Program
Products distributed
online from HICO/OSU
web site
Investigator
Proposal
Required
No cost
MERIS
300/1000 m
ENVISAT
(Jan 2002-Apr 2012)
European
Space
Agency
Free online access of
reduced resolution
datasets through 'My
Earthnet’ website
Access restrained data
sets by submitting a 'My
Earthnet' project
proposal
Registration
required
Investigator
Proposal
required
No cost
No cost
MODIS-Aqua
250/500/1000 m
Aqua
(EOS-PM1)
(May 2002 – present)
NASA
Ocean color products
along with metadata are
online at the Ocean Color
Data Processing System
at Goddard Space Flight
Center
Registration
required to
access online
browser
No cost
Space-based Coastal Ocean Color Sensors
ESA ENVISAT platform
MERIS = Medium Resolution Imaging Spectrometer
Relationship between chlorophyll and total nitrogen in estuarine waters
R² = 0.62 n = 147
Std error = 5.4 ug/L
0.0
10.0
20.0
30.0
40.0
50.0
0 500 1000 1500 2000
Ch
loro
ph
yll
a-m
ea
sure
d (
ug
/L)
Total Nitrogen-measured (ug/L)
R² = 0.49 n = 76
std error = 6.6 ug/L
0.0
10.0
20.0
30.0
40.0
50.0
0 500 1000 1500 2000
Ch
loro
ph
yll
a -
me
asu
red
(u
g/L
)
Total Nitrogen - measured (ug/L)
East Coast estuaries (including Neuse River estuary)
Neuse River Estuary only
*Datasets were collected by the USEPA Mid Atlantic
Integrated Assessment (MAIA-1998) and National Coastal Assessment (NCA) Programs (2000 -2004) as well as the Lower Neuse Basin Association (LNBA-1995 and 1998)
0.0
10.0
20.0
30.0
40.0
50.0
60.0
0 500 1000 1500 2000
Ch
l-a
- m
ea
sure
d (
ug
/L)
Total Nitrogen (ug/L)
~1800 ug/L ~1800 ug/L ~1800 ug/L ~1800 ug/L ~1800 ug/L ~1800 ug/L ~1800 ug/L ~1800 ug/L
NC WQ std
CBP SAV Threshold
Neuse River Estuary
~750 ug/L
0.0
10.0
20.0
30.0
40.0
50.0
60.0
0 500 1000 1500 2000
Ch
loro
ph
yll
a -
me
asu
red
(u
g/L
)
Total Nitrogen - measured (ug/L)
~1800 ~1800
CBP SAV Threshold
~1800
NC WQ Std
~700 ug/L
Comparison of Water Quality Thresholds using NC Water Quality and Chesapeake Bay Program Submerged Aquatic Vegetation Standards
Neuse River Estuary
15 ug/L
~1800 ug/L
Calibrating MERIS derived chlorophyll values to the Neuse River Estuary
R² = 0.84 n = 30
RSME = 6.8 μg/L
0
5
10
15
20
25
30
35
40
45
0 10 20 30 40
AM
S+
Fe
rry
Mo
n C
hl
a (
ug
/l)
MERIS Chl a (ug/l)
•FerryMon monitoring program from crossings (n = 19) during 2006 – 2009 of the Neuse River Bend and Lower Neuse River Estuary segments (Cedar Island/Orcacoke, Cherry Branch/Minnesott ) and in Pamlico Sound (Swan Quarter/Orcacoke) •NC DWQ Ambient Monitoring System (AMS) Chl a data collected along the Lower Neuse River Estuary segment (n= 11) from 2008- 2009. •The in situ data were collected at dates and times concurrent with MERIS overflights.
Chl a ambient = 1.3671 * (MERIS Chl a - 11.283)
Time Series of a TMDL Violation -
Neuse River Estuary: Winter -Spring 2007
January 29,2007
Chlorophyll a Concentration (ug/L)
< 10
10.1 - 20
20.1 - 30
30.1 - 40
40.1 - 50
50.1 - > 60
February 11, 2007
February 23, 2007
March 12, 2007
March 30, 2007
May 21, 2007
Chlorophyll a Concentration (ug/L)
< 10
10.1 - 20
20.1 - 30
30.1 - 40
40.1 - 50
50.1 - > 60
January 29, 2007
February 11, 2007
February 23, 2007
March 12, 2007
March 30, 2007
May 21, 2007
Time Series of a TMDL Violation Tar-Pamlico River Estuary:
Winter – Spring 2007
MERIS Chl a concentrations composited on an annual basis along the Neuse River Estuary
Chlorophyll a Concentration (ug/L)
< 10
10.1 - 20
20.1 - 30
30.1 - 40
40.1 - 50
50.1 - > 60
2006
2007
2008
2009
n = 12
n = 10
n = 34
n = 27
Neuse River Upper
Segment
Broad Creek
Cherry Point Marine Corp Air Station
Trent River
Slocum Creek
2006 Composite Image
Chlorophyll a Concentration (ug/L)
6.9 - 10
10.1 - 20
20.1 - 30
30.1 - 40
40.1 - 50
50.1 - > 60
Neuse River
Hancock Creek
Chlorophyll a Concentration (ug/L)
4.8 - 10
10.1 - 20
20.1 - 30
30.1 - 40
40.1 - 50
50.1 - > 60
2007 Chl a composite image
Greens Creek
Adams Creek South River
Broad Creek
Goose Creek
Neuse River
MERIS Chl a concentrations composited on an annual basis along the Tar-Pamlico River Estuary
Chlorophyll a Concentration (ug/L)
< 10
10.1 - 20
20.1 - 30
30.1 - 40
40.1 - 50
50.1 - > 60
2006
2007
2008
2009
n = 16 n = 33
n = 16 n = 27
2007 Chl a composite image
Chlorophyll a Concentration (ug/L)
< 10
10.1 - 20
20.1 - 30
30.1 - 40
40.1 - 50
50.1 - > 60
Tar-Pamlico River
2008 Chl a composite image
Chlorophyll a Concentration (ug/L)
< 10
10.1 - 20
20.1 - 30
30.1 - 40
40.1 - 50
50.1 - > 60
Tar-Pamlico
Date Neuse River Estuary Tar-Pamlico Estuary
Percentage of pixels that violate
the 10/40 criterion Impaired Acres
Percentage of pixels that
violate the 10/40 criterion Impaired Acres
3/4/2006 10.3 13,034 <10 -
1/26/2007 12.5 11,647 22.3 35,682
1/29/2007 16.5 21,090 28.1 44,878
2/11/2007 19.7 27,436 15.4 24,662
2/23/2007 27.1 34,504 26.3 41,990
2/24/2007 22.9 29,184 21.7 34,732
3/12/2007 15.0 19,095 10.9 17,461
3/18/2007 27.6 33,478 27.9 44,574
3/30/2007 24.6 31,312 13.2 21,166
1/1/2009 9.2 11,742 12.2 19,532
2/5/2009 10.9 13,927 10.9 17,385
2/15/2009 11.4 14,554 11.1 17,708
4/23/2009 <10 - 10.2 16,378
6/10/2009 <10 - 10.1 16,112
Total 261,003 352,260
Average 21,750 27,097
Assessment of the quantity of impaired acres during TMDL violations
Neuse River Estuary Impaired Acres derived from MERIS Chlorophyll
0
5000
10000
15000
20000
250001/
1/20
06
2/1/
200
6
3/1/
200
6
4/1
/20
06
5/1/
200
6
6/1
/20
06
7/1/
200
6
8/1
/20
06
9/1
/20
06
10/1
/20
06
11/1
/20
06
12/1
/20
06
Sa
ltw
ate
r Im
pa
ire
d A
cre
s
2006
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
1/1/
200
7
2/1/
200
7
3/1/
200
7
4/1
/20
07
5/1/
200
7
6/1
/20
07
7/1/
200
7
8/1
/20
07
9/1
/20
07
10/1
/20
07
11/1
/20
07
Sa
ltw
ate
r Im
pa
ire
d A
cre
s 2007
0
5000
10000
15000
20000
25000
1/1/
200
8
2/1/
200
8
3/1/
200
8
4/1
/20
08
5/1/
200
8
6/1
/20
08
7/1/
200
8
8/1
/20
08
9/1
/20
08
10/1
/20
08
11/1
/20
08
12/1
/20
08
Sa
ltw
ate
r Im
pa
ire
d A
cre
s 2008
0
5000
10000
15000
20000
25000
1/1/
200
9
2/1/
200
9
3/1/
200
9
4/1
/20
09
5/1/
200
9
6/1
/20
09
7/1/
200
9
8/1
/20
09
9/1
/20
09
Sa
ltw
ate
r Im
pa
ire
d A
cre
s 2009
0
5000
10000
15000
20000
250001/
1/20
06
2/1/
200
6
3/1/
200
6
4/1
/20
06
5/1/
200
6
6/1
/20
06
7/1/
200
6
8/1
/20
06
9/1
/20
06
10/1
/20
06
11/1
/20
06
12/1
/20
06
Sa
ltw
ate
r Im
pa
ire
d A
cre
s
2006
0
10000
20000
30000
40000
50000
60000
1/1/
200
7
2/1/
200
7
3/1/
200
7
4/1
/20
07
5/1/
200
7
6/1
/20
07
7/1/
200
7
8/1
/20
07
9/1
/20
07
10/1
/20
07
11/1
/20
07
Sa
ltw
ate
r Im
pa
ire
d A
cre
s
2007
0
5000
10000
15000
20000
25000
1/1/
200
8
2/1/
200
8
3/1/
200
8
4/1
/20
08
5/1/
200
8
6/1
/20
08
7/1/
200
8
8/1
/20
08
9/1
/20
08
10/1
/20
08
11/1
/20
08
12/1
/20
08
Sa
lwa
ter
Imp
air
ed
Acr
es 2008
0
5000
10000
15000
20000
25000
1/1/
200
9
2/1/
200
9
3/1/
200
9
4/1
/20
09
5/1/
200
9
6/1
/20
09
7/1/
200
9
8/1
/20
09
9/1
/20
09
Sa
ltw
ate
r Im
pa
ire
d A
cre
s 2009
Tar-Pamlico River Estuary Impaired Acres derived from MERIS Chlorophyll
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.01/
25/2
00
63/
16/2
00
65/
5/20
06
6/24/20…
8/1
3/20
06
10/2
/20
06
11/21/20…
1/10
/20
07
3/1/
200
74/20/20…
6/9
/20
07
7/29/20…
9/1
7/20
07
11/6
/20
07
12/26/2…
2/14
/20
08
4/4
/20
08
5/24/20…
7/13
/20
08
9/1
/20
08
10/21/20…
12/10/20…
1/29
/20
09
3/20/20…
5/9
/20
09
6/28/20…
8/1
7/20
09
ME
RIS
Ch
l a
(u
g/L
)
Mean Chl a - Neuse River Estuary
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
1/25
/20
06
3/16
/20
06
5/5/
200
66
/24
/20
06
8/1
3/20
06
10/2
/20
06
11/2
1/20
06
1/10
/20
07
3/1/
200
74
/20
/20
07
6/9
/20
07
7/29
/20
07
9/1
7/20
07
11/6
/20
07
12/2
6/2
00
72/
14/2
00
84
/4/2
00
85/
24/2
00
87/
13/2
00
89
/1/2
00
810
/21/
200
812
/10
/20
08
1/29
/20
09
3/20
/20
09
5/9
/20
09
6/2
8/2
00
98
/17/
200
9
ME
RIS
Ch
l a
(u
g/l
)
Mean Chl a Tar-Pamlico River Estuary
Mean chlorophyll a estimates: 2006 – 2009
Median chlorophyll a estimates: 2006 – 2009
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
1/25
/20
06
3/16
/20
06
5/5/
200
66
/24
/20
06
8/1
3/20
06
10/2
/20
06
11/2
1/20
06
1/10
/20
07
3/1/
200
74
/20
/20
07
6/9
/20
07
7/29
/20
07
9/1
7/20
07
11/6
/20
07
12/2
6/2
00
72/
14/2
00
84
/4/2
00
85/
24/2
00
87/
13/2
00
89
/1/2
00
810
/21/
200
812
/10
/20
08
1/29
/20
09
3/20
/20
09
5/9
/20
09
6/2
8/2
00
98
/17/
200
9
Median Chl a-Neuse River Estuary
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
1/25
/20
06
3/16
/20
06
5/5/
200
66/24/20…
8/1
3/20
06
10/2
/20
06
11/2
1/20
06
1/10
/20
07
3/1/
200
74
/20
/20
07
6/9
/20
07
7/29
/20
07
9/1
7/20
07
11/6
/20
07
12/26/20…
2/14
/20
08
4/4
/20
08
5/24
/20
08
7/13
/20
08
9/1
/20
08
10/21/20…
12/10/20…
1/29
/20
09
3/20
/20
09
5/9
/20
09
6/28/20…
8/1
7/20
09
chla
(u
g/L
)
Median Chl a Tar-Pamlico River Estuary
90th percentile chlorophyll a estimates:
2006 – 2009
0.0
20.0
40.0
60.0
80.0
100.0
1/25
/20
06
3/16
/20
06
5/5/
200
66
/24
/20
06
8/1
3/20
06
10/2
/20
06
11/2
1/20
06
1/10
/20
07
3/1/
200
74
/20
/20
07
6/9
/20
07
7/29
/20
07
9/1
7/20
07
11/6
/20
07
12/2
6/2
00
72/
14/2
00
84
/4/2
00
85/
24/2
00
87/
13/2
00
89
/1/2
00
810
/21/
200
812
/10
/20
08
1/29
/20
09
3/20
/20
09
5/9
/20
09
6/2
8/2
00
98
/17/
200
9
Ch
l a
(μ
g/L
)
90th percentile Chl a -Neuse River Estuary
0.0
20.0
40.0
60.0
80.0
100.0
1/25
/20
06
3/16
/20
06
5/5/
200
66
/24
/20
06
8/1
3/20
06
10/2
/20
06
11/2
1/20
06
1/10
/20
07
3/1/
200
74
/20
/20
07
6/9
/20
07
7/29
/20
07
9/1
7/20
07
11/6
/20
07
12/2
6/2
00
72/
14/2
00
84
/4/2
00
85/
24/2
00
87/
13/2
00
89
/1/2
00
810
/21/
200
812
/10
/20
08
1/29
/20
09
3/20
/20
09
5/9
/20
09
6/2
8/2
00
98
/17/
200
9
Ch
l a
(μ
g/L
)
90th percentile Chl a Tar-Pamlico River Estuary
NC Water Quality Violations in relation nitrogen reduction on land: Tar-Pamlico River Estuary
17,500,000
18,000,000
18,500,000
19,000,000
19,500,000
20,000,000
20,500,000
21,000,000
21,500,000
22,000,000
22,500,000
23,000,000
2006 2007 2008 2009
Nit
rog
en
on
la
nd
(lb
s)
Year
* Data source: Annual Report on the Tar-Pamlico Agricultural Rule - A Report to the NC Environmental
Management Commission from the Tar-Pamlico Basin Oversight Committee, Crop Years 2006, 2007, 2008 and 2009
7,556
19,775
18,697 17,360
0
5000
10000
15000
20000
25000
2006 2007 2008 2009
# M
ER
IS p
ixe
ls >
40
ug
/L
Year
Conclusions MERIS data can be successfully used for compliance
monitoring at the temporal and spatial scales needed for assessing water quality for the Neuse and Tar-Pamlico River estuaries.
The high resolution capability of MERIS data can provide data needed to assess the quantity of estuarine acres degraded by excess chlorophyll in estuarine waters.
90th percentile values of MERIS Chl a provide the most useful statistical value for compliance assessment and detection of TMDL exceedances.
Acknowlegements
Ross Lunetta (USEPA/NERL)
Diane Reid (NCDENR)
Kathy Stecker (NCDENR)
Research conducted under EPA ORD Safe and Sustainable Waters Research Program
MERIS data provided by the European Space Agency