01 Okuda Satoumi Okuda IJs
[Satoumi Special Session] 4 October 2017 (TBC)
S13：Development of Coastal Management
Ministry of
the Environment
Method to Realize a Sustainable Coastal Sea
Theme 1：Management of Nutrient Concentrations
in the Seto Inland Sea
Tetsuji Okuda
Presenter：
Ryukoku Univ.
Division delegate：Wataru Nishijima Hiroshima Univ.
Research delegate：Tetsuo Yanagi EMECS center
Hiroshima University
Kagawa University
1
Management of nutrients in enclosed coastal sea 2
Feedback
Nutrients Input
Phytoplankton blooms Red tide
Growth of
zooplanktons
and fishes
Positive side
Low transparency，
Growth inhibition of aquatic plants，
Increase of COD，
Hypoxia，Death of fishes，
Bad smell
Negative side
Act on Special Measures concerning Conservation
of the Environment of the Seto Inland Sea Oct. 2015
Coastal management for
“High productivity and sound material cycling”
Decrease of fish production
300,000
Total catch of fishes tons y-1
350,000
300,000
250,000
200,000
150,000
100,000
50,000
Planktivorous fish
All fish species - Planktivorous fish
250,000
全魚類
ランクトン食魚
ランクトン食魚
200,000
150,000
100,000
50,000
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
2012
2014
0
0
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
2012
2014
Total catch of fishes tons y-1
400,000
3
Total catch of fishes has decreased from mid-1980s to
recent years 51% .
Decrease in total catch of fishes
Planktivorous fish：from mid-1980s to 1990s
Other fishes：from 2000s to recent years
Nutrient loading from land
Nutrient loading data from MOE during 1981 and 2010 Seto inland sea
TN, TP (×10) load (tons y-1)
700
600
500
400
300
200
100
0
1981
-85
1986
-90
1991
-95
1996
-2000
2001
-05
2006
-10
TN and TP loading from land decreased to
40% and 61%, respectively, during last 30 years.
4
Grazing food chain
Predatory fishes
Benthic
Viewpoint of
Biological Production
Shellfish
Macro / Micro algae
Seagrass
.
5
Planktonic
Planktivorous fishes
Zooplanktons
Phytoplanktons
Viewpoint of
Regional Characteristics
N u t r i e n t s
.
Target (objectives)
6
Regional Characteristics of sea area
Characterization of extensive enclosed sea
from the viewpoint of “Phytoplankton growth”
Indices：Background Secchi Depth, Vulnerable Index
Identify a key area for nutrient control based on vulnerability
Biological Production
Evaluation of transfer efficiencies to higher trophic levels
according to phytoplankton abundance
Relationship between nutrient load curtailment from land
and biological productivity
Coastal management
Concept of coastal management in vulnerable areas
Quantification of nutrient uptake capacity in Seagrass beds
Tidal flats
8
Regional characteristics of sea area
Sunlight
Transparency
River Influence (nutrients, sands)
Depth and Wetland properties
Flow, Temparature, . . . .
9
Nutrients Input
Light environment
Distribution of secchi depth Mean value during 2005-’14
Light Intensity in Water⇔ Regional Water Quality
10
Background Secchi Depth BSD
11
Light attenuation coefficient m-1
Kd = Kwater + KCDOM + KTripton + Kphytoplankton
Data from MOE
1981-2014
BSD：Secchi depth without phytoplankton
Regional value eliminating the influence of eutrophication
MOE: Ministry of the Environment
BSD and Secchi depth improvement potential
Phytoplankton amount = Improvement Possibility
12
Parameters for Vulnerable Index
Vertical Fluidity
Freshwater (Nutrients) input
N 2 × 104 s−2
Salinity 1981-2010
Salinity of surface water
Autumn and winter data
Indicator of
nature-derived nutrients
from the land
13
2
N =
g
ρB
×
1981-2010
ρB − ρS
ZB − ZS
N 2： Väisälä frequencies s-2
g： Gravity m s-2
ρ： Density kg m-3
Z： Depth m
S： Surface， B：Bottom
Summer data
mixing intensity
Vulnerable Index VI
VI
14
MOE 127 Stns: 1981-2012
MLIT 229 Stns: 2003-2012
Stns where phytoplanktons have
bloomed >2 times were removed.
10％ value in Chl-a conc. : 5.8 µg L-1
Coefficients of the standardized
parameters in VI were estimated.
VI = 0.90×LogN2 - 1.05×Salinity - 1.05×BSD
N
MLIT: Ministry of Land, Infrastructure, Transport and Tourism
17
Biological production
Food sources of predatory fish
Hairtail Trichiurus lepturus
：Responsible for 55% of fish
catches of predatory fish
in last decade.
Stable isotope analysis
20
Decapodiformes
18
Engraulis japonicus
Ammodytes
personatus
16
Decapoda
Contribution %
δ15N ‰
22
T.
lepturus
18
14
-14
Stomach contents in T. lepturus
Cephalopoda
-18 -17 -16 -15
δ13C ‰
L. gracilis
-19
Decapoda
-21 -20
A. personatus
12
E. japonicus
Leptochela gracilis
Proportion of
individuals %
100
Hiuchi Nada during 2010-2013
75
A. personatus
50
L. gracilis
Decapoda
Cephalopoda
25
0
Planktonic
Month
E. japonicus
Other fishes
Squillidae
Polychaeta
Other
Crustacea
Benthic
Transfer efficiency onto oyster in a tidal flats 20
Sea lettuce
Microphytobenthos
30%
66%
Important food source
Short-necked clam
Contribution of microphytobenthos
as the food source of short-necked clam]
：56〜76% Stable isotope analysis
Transfer efficiency
: 10～14％
Relationship between Chl.a and transfer efficiency 22
Primary production
Transfer efficiency
3,000
2,000
Production (mgC m-2 d-1)
Transfer efficiency
0.8
3,500
1,000
0.6
0.4
0.2
0
0
0
Secondary production
600
10
20
30
40
50
60
70
Chl.a (μg L-1)
400
200
0
0
10
20
30
40
Chl.a (μg L-1)
50
60
70
Osaka Bay
Data collected in summer 2014-2015
Transfer efficiency decreased in high Chl.a concentration.
Primary production
of phytoplanktons
H1
H5
H2
H3
mgC m-2 d-1
Geographical difference of biological productivity 23
between coastal and offshore area
H7
H４
H6
mgC m-2 d-1
Secondary production
of zooplanktons
Coastal
H1-4,7
Offshore
H5,6
Primary production
mgC m-2 d-1
457
272
Secondary production
mgC m-2 d-1
12.9
27.8
Transfer efficiency ％
P.P. → S.P.
2.7
9.5
Annual mean
Although coastal area possess the high
primary productivity due to abundant
nutrient supply,
the transfer efficiency was relatively low.
Spatial difference of biological productivity
between coastal and offshore area
Not only topographical classification of the sea
area (Bay-Nada), but also Coastal-offshore
classification (management) is needed.
Coastal management in highly vulnerable areas 24
River
Nutrients
Zoo-Planktons
PhytoPlanktons
Fishes
Fishes
Transparency?
Structure (depth?)
Flow?
Mixing?
Temperature?
26
Coastal Management
< Sato Umi management >
Regional Individual Management
Possibility of improvement
27
Coastal management in highly vulnerable areas 29
River
Nutrients
Decomposition
Microalgae
Seagrass
Tidal flats
Benthos
Drifting during
autumn and winter
Denitrification
Fishes
Shellfish catch
Birds
Nutrient transport by seagrass：
Nutrient uptake during spring and summer
Drifting during autumn and winter
Decomposition in offshore area
Drifting seagrasses
Nutrient removal by seagrass
30
Subtidal zone
in Ikushima Bay
Seto Inland Sea
Seagrass beds
Zostera marina
Ikushima Bay
Outer bay
Area: 42 ha
Nutrients in winter
DIN: 3.4 µM
DIP: 0.43 µM
Nitrogen demand
160
Standing stock
0.36 kgN m-2
Unit: mgN m-2 d-1
Z. marina
Porewater (0-10 cm)
DIN：0.38 mgN m-2
152
?
Nutrient budget
in Ikushima Bay
May 2014
Estimation of nutrient uptake rate by Z. marina 31
Hiroshima Bay
Phytoplankton in seawater
152〜1,080 mgC m-2 d-1
Area-weighted mean: 399
Seasonal survey in 2015
Microphytobenthos in tidal flats
75〜395 mgC m-2 d-1
143 ± 92
July 2015〜June 2016
Nutrient loading from land
to Hiroshima Bay 2009
8,590 tN y-1
589 tP y-1
Zostera area covered
in 1960 597 ha
Zostera area covered
in 1996-’97 135 ha
540 tN y-1 6.3％
90 tP y-1 15.3％
122 tN y-1 1.4％
20 tP y-1 3.5％
If recovered..
References in other areas
Nabeta Bay (1979): 2,900 mgC m-2 d-1
Yanai Bay (1993): 3,900 mgC m-2 d-1
Ise Bay (2015): 3,570 mgC m-2 d-1
Z. marina in tidal flats
2,640〜24,000 mgC m-2 d-1
6,080 ± 5,800
July 2015〜June 2016
Line-transect survey July 2016
Zostera biomass in D.L. 0 to -1.5 m
Light attenuation in seawater
Relationship between light and
photosynthetic rate
C:N:P Weight ratio = 83:6:1
Productions in each D.L.
35
Wataru NISHIJIMA
Kuninao TADA
Satoshi NAKI
Youichi SAKAI
Takeshi TOMIYAMA Tetsuji OKUDA
PL Tetsuo YANAGI
36
S13：Development of Coastal Management
Ministry of
the Environment
Method to Realize a Sustainable Coastal Sea
Theme 1：Management of Nutrient Concentrations
in the Seto Inland Sea
Tetsuji Okuda
Presenter：
Ryukoku Univ.
Division delegate：Wataru Nishijima Hiroshima Univ.
Research delegate：Tetsuo Yanagi EMECS center
Hiroshima University
Kagawa University
1
Management of nutrients in enclosed coastal sea 2
Feedback
Nutrients Input
Phytoplankton blooms Red tide
Growth of
zooplanktons
and fishes
Positive side
Low transparency，
Growth inhibition of aquatic plants，
Increase of COD，
Hypoxia，Death of fishes，
Bad smell
Negative side
Act on Special Measures concerning Conservation
of the Environment of the Seto Inland Sea Oct. 2015
Coastal management for
“High productivity and sound material cycling”
Decrease of fish production
300,000
Total catch of fishes tons y-1
350,000
300,000
250,000
200,000
150,000
100,000
50,000
Planktivorous fish
All fish species - Planktivorous fish
250,000
全魚類
ランクトン食魚
ランクトン食魚
200,000
150,000
100,000
50,000
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
2012
2014
0
0
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
2012
2014
Total catch of fishes tons y-1
400,000
3
Total catch of fishes has decreased from mid-1980s to
recent years 51% .
Decrease in total catch of fishes
Planktivorous fish：from mid-1980s to 1990s
Other fishes：from 2000s to recent years
Nutrient loading from land
Nutrient loading data from MOE during 1981 and 2010 Seto inland sea
TN, TP (×10) load (tons y-1)
700
600
500
400
300
200
100
0
1981
-85
1986
-90
1991
-95
1996
-2000
2001
-05
2006
-10
TN and TP loading from land decreased to
40% and 61%, respectively, during last 30 years.
4
Grazing food chain
Predatory fishes
Benthic
Viewpoint of
Biological Production
Shellfish
Macro / Micro algae
Seagrass
.
5
Planktonic
Planktivorous fishes
Zooplanktons
Phytoplanktons
Viewpoint of
Regional Characteristics
N u t r i e n t s
.
Target (objectives)
6
Regional Characteristics of sea area
Characterization of extensive enclosed sea
from the viewpoint of “Phytoplankton growth”
Indices：Background Secchi Depth, Vulnerable Index
Identify a key area for nutrient control based on vulnerability
Biological Production
Evaluation of transfer efficiencies to higher trophic levels
according to phytoplankton abundance
Relationship between nutrient load curtailment from land
and biological productivity
Coastal management
Concept of coastal management in vulnerable areas
Quantification of nutrient uptake capacity in Seagrass beds
Tidal flats
8
Regional characteristics of sea area
Sunlight
Transparency
River Influence (nutrients, sands)
Depth and Wetland properties
Flow, Temparature, . . . .
9
Nutrients Input
Light environment
Distribution of secchi depth Mean value during 2005-’14
Light Intensity in Water⇔ Regional Water Quality
10
Background Secchi Depth BSD
11
Light attenuation coefficient m-1
Kd = Kwater + KCDOM + KTripton + Kphytoplankton
Data from MOE
1981-2014
BSD：Secchi depth without phytoplankton
Regional value eliminating the influence of eutrophication
MOE: Ministry of the Environment
BSD and Secchi depth improvement potential
Phytoplankton amount = Improvement Possibility
12
Parameters for Vulnerable Index
Vertical Fluidity
Freshwater (Nutrients) input
N 2 × 104 s−2
Salinity 1981-2010
Salinity of surface water
Autumn and winter data
Indicator of
nature-derived nutrients
from the land
13
2
N =
g
ρB
×
1981-2010
ρB − ρS
ZB − ZS
N 2： Väisälä frequencies s-2
g： Gravity m s-2
ρ： Density kg m-3
Z： Depth m
S： Surface， B：Bottom
Summer data
mixing intensity
Vulnerable Index VI
VI
14
MOE 127 Stns: 1981-2012
MLIT 229 Stns: 2003-2012
Stns where phytoplanktons have
bloomed >2 times were removed.
10％ value in Chl-a conc. : 5.8 µg L-1
Coefficients of the standardized
parameters in VI were estimated.
VI = 0.90×LogN2 - 1.05×Salinity - 1.05×BSD
N
MLIT: Ministry of Land, Infrastructure, Transport and Tourism
17
Biological production
Food sources of predatory fish
Hairtail Trichiurus lepturus
：Responsible for 55% of fish
catches of predatory fish
in last decade.
Stable isotope analysis
20
Decapodiformes
18
Engraulis japonicus
Ammodytes
personatus
16
Decapoda
Contribution %
δ15N ‰
22
T.
lepturus
18
14
-14
Stomach contents in T. lepturus
Cephalopoda
-18 -17 -16 -15
δ13C ‰
L. gracilis
-19
Decapoda
-21 -20
A. personatus
12
E. japonicus
Leptochela gracilis
Proportion of
individuals %
100
Hiuchi Nada during 2010-2013
75
A. personatus
50
L. gracilis
Decapoda
Cephalopoda
25
0
Planktonic
Month
E. japonicus
Other fishes
Squillidae
Polychaeta
Other
Crustacea
Benthic
Transfer efficiency onto oyster in a tidal flats 20
Sea lettuce
Microphytobenthos
30%
66%
Important food source
Short-necked clam
Contribution of microphytobenthos
as the food source of short-necked clam]
：56〜76% Stable isotope analysis
Transfer efficiency
: 10～14％
Relationship between Chl.a and transfer efficiency 22
Primary production
Transfer efficiency
3,000
2,000
Production (mgC m-2 d-1)
Transfer efficiency
0.8
3,500
1,000
0.6
0.4
0.2
0
0
0
Secondary production
600
10
20
30
40
50
60
70
Chl.a (μg L-1)
400
200
0
0
10
20
30
40
Chl.a (μg L-1)
50
60
70
Osaka Bay
Data collected in summer 2014-2015
Transfer efficiency decreased in high Chl.a concentration.
Primary production
of phytoplanktons
H1
H5
H2
H3
mgC m-2 d-1
Geographical difference of biological productivity 23
between coastal and offshore area
H7
H４
H6
mgC m-2 d-1
Secondary production
of zooplanktons
Coastal
H1-4,7
Offshore
H5,6
Primary production
mgC m-2 d-1
457
272
Secondary production
mgC m-2 d-1
12.9
27.8
Transfer efficiency ％
P.P. → S.P.
2.7
9.5
Annual mean
Although coastal area possess the high
primary productivity due to abundant
nutrient supply,
the transfer efficiency was relatively low.
Spatial difference of biological productivity
between coastal and offshore area
Not only topographical classification of the sea
area (Bay-Nada), but also Coastal-offshore
classification (management) is needed.
Coastal management in highly vulnerable areas 24
River
Nutrients
Zoo-Planktons
PhytoPlanktons
Fishes
Fishes
Transparency?
Structure (depth?)
Flow?
Mixing?
Temperature?
26
Coastal Management
< Sato Umi management >
Regional Individual Management
Possibility of improvement
27
Coastal management in highly vulnerable areas 29
River
Nutrients
Decomposition
Microalgae
Seagrass
Tidal flats
Benthos
Drifting during
autumn and winter
Denitrification
Fishes
Shellfish catch
Birds
Nutrient transport by seagrass：
Nutrient uptake during spring and summer
Drifting during autumn and winter
Decomposition in offshore area
Drifting seagrasses
Nutrient removal by seagrass
30
Subtidal zone
in Ikushima Bay
Seto Inland Sea
Seagrass beds
Zostera marina
Ikushima Bay
Outer bay
Area: 42 ha
Nutrients in winter
DIN: 3.4 µM
DIP: 0.43 µM
Nitrogen demand
160
Standing stock
0.36 kgN m-2
Unit: mgN m-2 d-1
Z. marina
Porewater (0-10 cm)
DIN：0.38 mgN m-2
152
?
Nutrient budget
in Ikushima Bay
May 2014
Estimation of nutrient uptake rate by Z. marina 31
Hiroshima Bay
Phytoplankton in seawater
152〜1,080 mgC m-2 d-1
Area-weighted mean: 399
Seasonal survey in 2015
Microphytobenthos in tidal flats
75〜395 mgC m-2 d-1
143 ± 92
July 2015〜June 2016
Nutrient loading from land
to Hiroshima Bay 2009
8,590 tN y-1
589 tP y-1
Zostera area covered
in 1960 597 ha
Zostera area covered
in 1996-’97 135 ha
540 tN y-1 6.3％
90 tP y-1 15.3％
122 tN y-1 1.4％
20 tP y-1 3.5％
If recovered..
References in other areas
Nabeta Bay (1979): 2,900 mgC m-2 d-1
Yanai Bay (1993): 3,900 mgC m-2 d-1
Ise Bay (2015): 3,570 mgC m-2 d-1
Z. marina in tidal flats
2,640〜24,000 mgC m-2 d-1
6,080 ± 5,800
July 2015〜June 2016
Line-transect survey July 2016
Zostera biomass in D.L. 0 to -1.5 m
Light attenuation in seawater
Relationship between light and
photosynthetic rate
C:N:P Weight ratio = 83:6:1
Productions in each D.L.
35
Wataru NISHIJIMA
Kuninao TADA
Satoshi NAKI
Youichi SAKAI
Takeshi TOMIYAMA Tetsuji OKUDA
PL Tetsuo YANAGI
36