Remote sensing application for
monitoring and assessment of
eutrophication
in the NOWPAP region
Joji Ishizaka
(Nagasaki University)
Outline
• Definition and Consequence of
•
•
•
•
Eutrophication
Toyama Bay
South Sea of Korea Red Tide
East China Sea and Yellow Sea
Ariake Bay Red Tide
Definition of Eutrophication
• Accumulation of nutrients and organic
matter to lake and coastal environments
and resulted changes of ecosystem.
• Natural: Long term succession.
• Anthropogenic (Human(Human-made): Discharge
of waist, fertilizer etc.
1
Consequence of Eutrophication
• Increase of Red Tide (HAB: harmful algal
bloom)
• Decrease of Low Dissolved Oxygen
Condition
• Mass Mortality to Organisms
Bottom-up Control
(vs. Top-down Control)
Fish Yield
⇑
Ecosystem Structure (trophic
(trophic level)
⇑
Primary Production
⇑
Environments
(Nutrients)
Food
Chain
Lalli and Parsons
2
Global CHLCHL-a
Most of the ocean is oligotrophic!
oligotrophic!
Paradox of Eutrophication
• Phytoplankton: Primary Producer
Oligotrophic Environment – Low Productivity
• Large Area is Oligotrophic
Fishing Ground – Upwelling Area (Natural
Eutrophication)
Appropriate Amount of Nutrient is
Necessary!
What is Appropriate Amount?
Before Eutrophication
Organic
Materials
Nutrients
Organic
Materials
Nutrients
Organic
Materials
Nutrients
Fishing
Harvest
Phyto
plankton
Zoo
plankton
Fish/Clam
Sedimentation
3
After Artificial Eutrophication
Fishing
Harvest
Human Pollution
Red
Tide
Organic
Materials
Organic
Materials
Nutrients
Blue
Tide
Phyto
plankton
Zoo
plankton
Fish/Clam
Oxygen
Depletion
Nutrients
Sedimentation
How we can use remote sensing to
monitoring of eutrophication.
• Direct observation of change
• Check of appropriate location of ship
observation
• Check of background level
• - chlorophyllchlorophyll-a, red tide
• - SST, altimeter,,
Toyama Bay Project
Monitoring in situ Survey of Toyama Bay
– Observed Variable with Vessel
Temperature, Salinity, Water Color,
Transparency, Remote Sensing Reflectance
– Analyzed Variable in Lab
Dissolved Oxygen, COD
Phosphate, Nitrogen and Silicate
ChlChl-a, Suspended Solid, CDOM,
4
Analysis of MODIS ChlChl-a Daily Images
Anti-clockwise
flow pattern
Two peaks of Chl-a
concentration one in
early spring and the
other in fall every year
Monthly SeaWiFS ChlChl-a
Data Aanalysis (98(98-03)
Chl-a concentration of
inner are of the Bay
become higher every
summer
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
1998
1999
2000
2001
No valide data
available
2002
2003
Seasonal Variability
of Satellite
Chlorophyll a
1997~2002
Chlorophyll a ＞ 0.8 μg l-1
(Yamada et al.)
5
Outer
Seasonal variability of
SeaWiFS Chl.a from each
sampling points
Middle
Inner
InterInter-annual Variation
of Coastal SeaWiFS
ChlChl-a Concentration
(98(98-03)
1998
1999
2000
2001
2002
2003
Validation of SeaWiFS Data
6
Comparison of in situ ChlChl-a and
COD (Chemical Oxygen Demand)
Strong positive
correlation
(R = 0.87, N =86)
Less variability was
found in spring and
summer.
Transport of
C. Polykrikoides
Red Tide？
(MODIS, JAXA)
3. Results and Discussions
1. 10 sub-samples collected from various water condition based on true color and chlorophyll images
Sep. 8 , 2002
(a)
Aug. 19, 2002
True Color from
MODIS bands (645, 555,469 nm).
(d)
MODIS Chlorophyll Con. (b)
(e)
(c)
(NFRDI, 2004)
(Son, Y.B. et al., In prep.)
7
3. Results and Discussions : Spectral characteristic of sub-samples
Bright color (B1, B2) : Radiance peaks at green band.
High radiance and particulate backscattering but phytoplankton absorption is minimal
High chlorophyll and red tide (H, R) : Radiance peaks at green band
High absorption of the phytoplankton and gelbstoff/detritus .
Particulate backscattering values are ~3-4 times lower than in bright color samples.
Low and moderate chlorophyll (L, M) : Radiance peaks from 412 nm to 531 nm (blue to green bands)
absorption and backscattering of the phytoplankton, gelbstoff, and detritus in all visual wavelengths
3. Results and Discussions : Scheme for identifying the water types
Step 1
Step 3
Yes
No
No
667 nm >678 nm
No
Step 2
No
Max(531 & 551 nm)
Step 4-1
Step 4
Highest peak
at 412 nm
Step 2-1
Highest peak at 551 nm
Step 4-2
Ye
s
Yes
Yes
No Radiance ratio of 412/443 is
greater than that of 531/551
Step 4-3
No
Yes
No Radiance ratio of 412/488 is
greater than that of 531/551
No values at
748 and 869 nm
Step 2-2
Yes
Yes
Turbid Water
Red
Tide
Mixed Water
Clear
Water
Intermediate Water
Step 1: The maximum peaks in blue-to-green wavelengths to separate largely two different water types.
Step 2: Determining intermediate and clear waters.
step 2-1 used the highest peak at nLw(412).
Step 2-2 used that the values of nLw(748) and nLw(869) are zero.
Step 3: Turbid and mixed waters included red tide water.
Turbid water used nLw(667) > nLw(678) and mixed water as nLw(667) < nLw(678).
3. Results and Discussions : Identify the water types
19%
81%
Step 1
3%
23%
9%
Step 3:nLw(667)>nLw(678)
16%
72%
Step 2
CW
IW
TW
Step 2
43%
33%
Step 3:nLw(667)<nLw(678)
Step 2
Sep. 8, 2002
Aug. 19, 2002
LC
1%
Step 3:nLw(667)>nLw(678)
Step 2
Step 3:nLw(667)<nLw(678)
44%
56% Step 1
MW
LC
CW
IW
TW
MW
8
3. Results and Discussions : HABs Detection
Aug. 19, 2002
Sep. 8, 2002
Step 4-1 : nLw(551) is highest peak among
The 9 visible bands of MODIS
Step 4-2 :
Step 4-3 :
(NFRDI, 2004)
(NFRDI, 2004)
Increase
of China
Coastal
Area in
the East
China
Sea
（Zhu,
2003）
2003）
10-year average Chl-a
Jan
Feb
May
June
Sep
Oct
Mar
July
Nov
Apr
Aug
Dec
9
10-year average nLw555 (Sediment)
Jan
Feb
Mar
Apr
May
June
July
Aug
Sep
Oct
Nov
Dec
High chl.a area and
Low Salinity Water
(Kim et al.,
Submitted)
Distribution of month of maximum
10
Distribution of month of maximum
Seasonal Changes in Each Area
10
8
6
4
2
0
10
8
6
4
2
0
10
8
6
4
2
0
JFMAMJJASOND
10
8
6
4
2
0
JFMAMJJASOND
10
8
6
4
2
0
JFMAMJJASOND
10
8
6
4
2
0
JFMAMJJASOND
JFMAMJJASOND
10
8
6
4
2
0
JFMAMJJASOND
JFMAMJJASOND
JFMAMJJASOND
10
8
6
4
2
0
長江
省
JFMAMJJASOND
10
8
6
4
JFMAMJJASOND 2
0
10
8
JFMAMJJASOND
6
4
2
0
江
10
8
6
4
2
0
10
8
6
4
2
0
浙
10
8
6
4
2
0
10
8
6
4
2
0
JFMAMJJASOND
JFMAMJJASOND
10
8
6
4
2
0
10
8
6
4
2
0
JFMAMJJASOND
JFMAMJJASOND
JFMAMJJASOND
Changjiang Diluted Water
10
Area 15
8
6
4
2
0
JFMAMJJASOND
10
Area 13
8
6
4
2
0
10
8
6
4
2
0
10
8
6
4
2
0
10
8
6
4
2
0
10
8
6
4
2
0
JFMAMJJASOND
JFMAMJJASOND
10
8
6
4
2
0
JFMAMJJASOND
JFMAMJJASOND
10
8
6
4
2
JFMAMJJASOND 0
JFMAMJJASOND
JFMAMJJASOND
JFMAMJJASOND
10
8
6
4
2
0
長江
浙
10
Area 12
8
6
4
JFMAMJJASOND 2
0
10
Area 9
8
JFMAMJJASOND
6
4
2
0
JFMAMJJASOND
省
10
Area 14
8
6
4
2
0
江
10
Area 16
8
6
4
2
0
10
8
6
4
2
0
JFMAMJJASOND
Area 4
JFMAMJJASOND
10
Area 11
8
6
4
2
0
JFMAMJJASOND
(Yamaguchi et al., In prep.)
10
8
6
4
2
0
Area 5
JFMAMJJASOND
11
Changjiang Diluted Water
JFMAMJJASOND
10
Area 15
8
6
4
2
0
JFMAMJJASOND
10
Area 13
8
6
4
2
0
10
8
6
4
2
0
10
8
6
4
2
0
10
8
6
4
2
0
JFMAMJJASOND
10
8
6
4
2
0
JFMAMJJASOND
10
8
6
4
2
0
JFMAMJJASOND
JFMAMJJASOND
10
8
6
4
2
JFMAMJJASOND 0
JFMAMJJASOND
JFMAMJJASOND
10
8
6
4
2
0
長江
浙
10
Area 12
8
6
4
JFMAMJJASOND 2
0
10
Area 9
8
JFMAMJJASOND
6
4
2
0
省
10
Area 14
8
6
4
2
0
江
10
Area 16
8
6
4
2
0
10
8
6
4
2
0
JFMAMJJASOND
10
Area 11
8
6
4
2
0
JFMAMJJASOND
Area 4
JFMAMJJASOND
10
8
6
4
2
0
JFMAMJJASOND
Area 5
JFMAMJJASOND
Interannual Variability of
Chl-a and Changjiang Discharge on May-Oct.
1.2
1
(Lag= 1)
4
0.2
2
R=0.43
P<0.01
chl-a (mg/m3)
0
0
4
4
4
4
0x10 2x10 4x10 6x10 8x10
12
10
(Lag= 0)
3
2
1
R=0.57
P<0.01
0
0
4
4
4
4
0x10 2x10 4x10 6x10 8x10
(Lag= 0)
R=0.70
P<0.01
0
0
4
4
4
4
0x10 2x10 4x10 6x10 8x10
1
4
0.6
0.4
3
(Lag= 2)
0.8
(Lag= 2)
1.4
1.2
1
0.8
0.6
0.4
R=0.67
0.2
P<0.01
0
0
4
4
4
4
0x10 2x10 4x10 6x10 8x10
CRD (m3/s)
8
6
4
2
R=0.27
P=0.12
0
0
4
4
4
4
0x10 2x10 4x10 6x10 8x10
Correlation between Chl-a and
Discharge with Lag 0-2 months
12
Interannual Variability
in the Yellow Sea
Spring
Summer
Changjiang
Discharge
Chl.a
nLw555
○
Increase of Frequency of Intense
Algal Blooms in the Yellow Sea
Nutrient Changes in the Yellow Sea
13
YOC Verification Project
（Yellow Sea Large Marine
EcosystemEcosystem- Ocean Color Project）
Project）
Standard_chlorophyll_concentration
New_chlorophyll_concentration
14
120
50
130
140
150
40
30
33.5
Location
of the
Ariake
Sound
20
Isahaya Bay
33.0
Reclamation Area
1996～
32.5
32.0
129.5
130.0
130.5
131.0
Eutrophication in Ariake Bay?
- Symptom of eutrophication
• Red tide increase
• Low oxygen condition
However:
• No nutrient load increase
• Dike Construction on 1998
諫早湾干拓（ASTER）
15
Isahaya Dike
Red Tide in Ariake Bay in Winter 20002000-01
Nori (red algae) Culture
40% ($200M!) Loss
Comparison with Red Tide Map
Produced by Nagasaki Fisheries
Experimental Station
July 8-13, 2001
有明海
Jul 9,2001
Nov. 9-Dec. 6, 2001
有明海
Nov 22,2001
（ ：Observed Area）
16
Red
Tide
in
Ariake
Bay
Relcamation
Area
SeaWiFS (2000.11.23-2001.4.1)
Monthly SeaWiFS Chl.a
1
2
3
4
5
6
7
0.01
8
9
0.1
10
64
10 11 12
98
99
00
01
02
03
04
17
Chl.a (mg m-3)SEA LEVEL (cm)
Spring
Neap
3.0
2.5
2.0
1.5
1.0
Spring
5
Chl.a
64
10
nLw 555
1
0.1
0.05
3
1
0.1
0.05
3 5
9 10 11 14 16 24
nLw555
(mW cm-2
μm-1 sr-1)
700
600
500
400
300
200
100
20
16
12
8
4
Turbidity and
Chlorophyll
Change with
Tidal Cycle
(SeaWiFS)
October, 2002
Red Tide
Number
in Ariake
Sound
（Isobe，
2000）
85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00
3030-year Increase of transparency
Value (m)
% Change
18
Ariake Bay Hypothesis
• Decrease of Tidal Flat (Not only Isahaya
Bay)
• Decrease of Tidal Current
• Decrease of Transparency
• Increase of Available Light to
Phytoplankton
• Increase of Red Tide
• Increase of Low Oxygen Water
• Dec
D ease off Clam
Cl
Use of Remote Sensing for
Eutrophication Monitoring
•
•
•
Large Spatial Coverage
High Frequency
Low Price
However
• Period is still limited for 10 years.
• Accuracy have to be checked.
• Cause and effect is not clear.
• Combination with shipship-observation is necessary.
19