Field Survey for Refractory Organic Matter Quantity in the Marine Sediment of Ise Bay and Evaluation of Its Effect on the Persistency of Hypoxic Water Generation

$Field Survey for Refractory Organic Matter Quantity in the Marine Sediment of Ise Bay and Evaluation of Its Effect on the Persistency of Hypoxic Water Generation$

Field Survey for Refractory Organic Matter Quantity in the Marine Sediment of Ise Bay and Evaluation of its Effect on the Persistency of Hypoxic Water Generation

◎Satoshi CHIBA, Maki OYAGI, Yokkaichi University Hideki KOKUBU, Mie Prefecture Fisheries Research Institute Yoshinori TANIMURA, Haruki AMANO, Mie Prefecture Health and Environment Research Institute Junji NIINOMI, Mie Prefectural Sewerage Management Public Corporation Kensuke TAKENOUCHI, International Center for Environmental Technology Transfer Toshiyuki KOBAYASHI, Department of Environmental and Social Affairs, Mie Prefectural Government Objectives

1. To investigate the spatial distribution and other characteristics of refractory organic matter(ROM) in the marine sediment in Ise Bay by the field survey. 2. To elucidate its effect on the chronic generation of hypoxic water with the aid of a marine sediment - pelagic ecosystem coupled model. Location and Bathymetry of Ise Bay

Islands of Japan Kiso Nagoya Rivers Sampling Sites A1-A6 35’00” Yokkaichi A1 A2 Bay Head Station Chita Peninsula Chita Bay Suzuka A3 Gamagori Ise Tsu Bay A4 A5 A6 34’40” Atsumi Bay Atsumi Peninsula

Matsusaka Information of Ise Bay 2

Horizontal Area: abt.2000km 0 10 20km Ise Toba Pacific

Mean Water Depth: 20m

” Ocean Population in the watershed area :

Shima

136’40” 137’00 10.5 mil. 34’20” 137’20” Nutrient Load from the Watershed

原単位法による計算値（千葉） Total Nitrogen Published values by the Start of Ministry of Environment Regulation of Japan (MOE) For Total Pollutant Load Estimated values by the Unit Load Method (Chiba, 2015)

Total Phosphorus

Same as above. Number of Occurrences of Red Tide in Ise Bay Start Year of Regulation for Total Pollutant Load Data from Ministry of Environment

stagnation

Ratio to Yearly Change of Hypoxic Water Area bay area Data from Mie Prefecture No change Estimation for the Mechanism of Prolongation of Hypoxic Water Generation with the Existence of Refractory Organic Matter

Bay Head

Sea Surface Bay Mouth OuterSea

Primary Production

Oxygen Consumption Sea Water By Seawater POM DOM Nutrients Oxygen Consumption Hypoxic by sediment Water Nutrients

Sea Floor

Labile OM Refractory OM Thickness < 1cm Thickness 20～100cm Field Sampling of Sediment Cores

2015 Oct.15 and Oct.29 Sedimentation Rate 0.5

More than 5 times unit: gcm-2y-1

0.1

Mean Sedimentation rate in the last 50 years

Reference: X. Lu, E. Matsumoto, “Recent sedimentation rates derived from 210Pb and 137Cs methods in Ise Bay, Japan”, Estua-rine, Coastal and Shelf Science, vol.65, Iss.1–2, pp.83–93, 2005. Vertical Profile of TOC in the Sediment Date Non-degradable 2015 component Date 2015 2009 2002 2003 1985 1996 1968 1989 1943 1982 1901 1974 St.A2 1853 1965 1954 St.A3 1816 1757 Date 2015 1995 1966 1928 1879 1830 1773 St.A5 1711 1650 Note: The concentration of labile organic matter is very small and almost invisible . Averaged TOC concentration Total Quantity of d-TOC near the Surface (mgC/g) (mg/cm2)

19.4 169 21.5 A2 231 A2 A1 A1 130 34.6 A3 H L 29.0 27.1 17.8 71 114 162 A4 A5 A6 A4 A5 A6

unit: mgC/g unit: mgC/cm2 Time and Rate Constants for the Degradation Process of Refractory Organic Matter

Tot. Qty. Time Rate Location TOC Con. Sed. Rate TOC Const. No. (mg/g) (g/cm2y) Const. (mg/cm2) (y) (1/y) A3 130 18.7 0.15 47 0.021 A4 71 15.4 0.15 31 0.033 A5 80 14.6 0.11 50 0.020 A6 114 9.5 0.20 60 0.017

Average 47 0.021 Numerical Models

3D Hydrodynamic Model

Developed during 2003 to 2005 by Not Coupled. S.Chiba, et.al.

Low Trophic Pelagic Ecosystem Model

Developed during 2005 to 2007 by S.Chiba, Coupled et.al.

Early Diagenesis Model of Sediment

Developed during 2005 to 2007 by K.Anggara, S.Chiba, et.al. Low Trophic Pelagic Ecosystem Model

Inflow from Watershed Area Sun Ray Atmospheric Oxygen Sea Surface

Exchange with Outer Sea Photosynthesis Dissolved Consumption by OM dissolution Oxygen Consumption by sediment

Diatom respiration respiration DIP Predation Zooplankton

DIN Release Release Egestion Death Cell Death Quota Uptake

Mineralization DIP POC Minerali- Dis- DIN zation DOC solution POP

DOP PON

DON Effluent Settling Resuspension

Settling Effluent

Sediment Model Early Diagenesis Sediment Model Bio-Geochemical Reactions

Oxygen Respiration De- nitrification Manganese Reduction Iron Reduction Sulfate Reduction

Phosphorous Mineralization

Modified from Fossing et al. Early Diagenesis Sediment Model

Model Equations

Model Geometry (1-D)

DBL Sea Upper Boundary

Bed

Computational

Cell

cm in depth, 60 GridPoints depth, in cm 60

70 70

- 40

Bottom Boundary Simulation Cases External Conditions Weather Condition Simulation Case No. River Discharge Condition Purpose Period Tidal Condition Boundary Cond. at Outer Sea 1950 to Investigation of Long- Case 1 Fixed to the data of 2010 2039 Term Response 1986 to Confirmation of Case 2 Applied the data of each year 2015 Accuracy of Models

Nutrient Loading From Watershed (Pattern 1)

Ratio to the Load at 2010 Horizontal Contour of Dissolved Oxygen Concentration above the Seafloor Observation Data surveyed by Mie prefecture Year 2010

Simulation (Case 2)

June July August September October Yearly Change of Hypoxic Water Area

Observation Data from Mie prefecture

Simulation (Case 2) Yearly Change of d-TOC Quantity and Hypoxic Water Area Case 1

Average of d-TOC Quantity

delay effect of excess ROM

effect of excess ROM

Loading Pattern of Nutrient Horizontal Distribution of TOC at the Sediment Surface Case 1 (mgC / g) Simulation Simulation Simulation

1950 1970 1990 L Simulation Simulation

L L Observation

2010 2040 Transient and Steady State Calculation Done in Case 1 calculation Transient Calculation Solution depends on the nutrient loading history of previous years.

Steady State Calculation Calculation continues for about 100 years to get a stable solution with the fixed nutrient loading of the designated year. Comparison of Transient and Steady State Solution Refractory Organic Matter in the Sediment Year 2010 Case 1

A2 A5 Transient Steady State Solution Solution

Steady State Solution

Transient Observation Data Solution Observation Data

Quantity of d-TOC for the entire bay Transient Steady State Ratio

d-TOC (g/cm2) 196 166 1.18 Comparison of Transient and Steady State Solution Extent of Hypoxic Water

2010 September 6

Hypoxic Water Area

L L

(mg / l)

Transient Steady State Transient Steady State Ratio

Hypoxic Water Area (km2) 740 666 1.11

Hypoxic Water Volume (km3) 7.47 6.33 1.18

Average of July to September of 2010 Nitrogen Budget in Primary Production Year Average of 2010 Unit: tonN/day Total of Entire Bay 8.3 20.6 90.8 River NH4 NH4 118.3 12.0 4.8 PhytoPl. 119.1 PON 23.4 13.5 N2 NO3 18.6 4.8 19.8 54.8 DON NH4 Up. PON 79.4 104.1 157.3 72.6 NO3 DON NO3 Up. 53.3 31.6 259.9 Sediment NH4 56.6 61.3 9.5 7.2 22.8 N2 NH4 DON 3.6 140.8 -1.5 14.6 240.2 PON NO3 ZooPl. 35.2 DON 14.8 14.3 5.9 Ocean NH4 Ocean 104.5 5.4 1.2 PON 19.7 11.5 N2 47.4 1.1 5.7 DON 31.1 36.9 22.1 Ocean NO3 T-N and T-P Uptake Rate in Primary Production

571 558

417 396 325 298 417/396 = 1.05

79.6 74.3

55.1 52.0 43.6 40.0 55.1/52 = 1.06 Summary

Field survey Results  Age Distribution of d-TOC: Disclosed  Distribution of d-TOC Conc.: Maximum at Bay Central area  Distribution of d-TOC Quantity: Minimum at Bay Central area  Characteristic Time of ROM Decomposition: abt. 47 years

Simulation Results  Prolongation of Hypoxic Water Generation: Reproduced  Hypoxic Water Area Increase due to excess ROM: abt.11%  Hypoxic Water Volume Increase due to excess ROM: abt.18%  Increase of Nutrient Up-Take by Phytoplankton due to excess ROM: abt. 5 to 6% Number of Occurrences of Red and Blue Tide Start Year of Regulation for Total Pollutant Load in Ise Bay Data from Ministry of Environment Red Tide stagnation

year delay Blue Tide

stagnation

year COD Concentration in Surface Water N2

N9 T-N & T-P Con. in Surface Water Start Year of Regulation for Total Pollutant Load

N8 N4

N9 N4

N8 Data from N9 Ministry of Environment Yearly Change of Hypoxic Water Area and Volume Observation data Hypoxic Water Area （ratio to total bay area）

Hypoxic Water Volume （ratio to total bay volume） Sedimentation Rate

M0(0.71) unit: H -2 -1 A1 A2 gcm y M0.5(0.13)

IS14(0.33) A3

M1(0.19) I1.0(0.17)

IS12(0.05) M1.5(0.12) A6 A5 A4 L IS9(0.05) M2(0.19) I2.0

Year Mean Sedimentation rate in the last 50 years

Date 2015 2002 1985 1968 1943 1901 1853

St.A3 1816 1757 Vertical Profile of TOC in the Sediment Non-degradable Date component Date 2015 2015 1999 1995 1975 1966 1943 1928 1912 1879 1879 1830 1841 1773 St.A4 1804 St.A5 1711 1765 1650

Date 2015 1991 1962 1930 1897 1865 1825

St.A6 1783 1741 Averaged TOC concentration for the layer from the seafloor to 3cm depth unit: mgC/g

19.4 21.5 A2 A1

34.6 A3 H

29.0 27.1 17.8 A4 A5 A6

unit: mgC/g Total Quantity of Degradable Total Quantity of Degradable and TOC (mg/cm2) Non-Degradable TOC (mg/cm2)

169 231 A2 A1 130

L 71 114 162 A4 A5 A6

Ensemble Average of d-TOC: 146 mg/cm2 unit: mgC/cm2

Estimation of Total quantity of d-TOC for the Entire Bay: 1.77×108 ton Derivation of Decomposition Rate of d-TOC from the Profile Data C d-TOC quantity z,t in the shaded area is z  z,t  t

C(1)z  CSt. z,t Symbols z : depth t : time (deposited time) C : Concentration of d-TOC at depth z or deposited t years ago ρ : Density of solid part of the sediment φ : Porosity

S : Sedimentation rate t years ago Derivation of Decomposition Rate from the Profile Data

T1 G  C(t)S(t)dt Eq.(1) T 0

G : Quantity of d-TOC from T0 to T1 C(t) : Present concentration of d-TOC deposited t years ago

S(t) : Sedimentation rate t years ago

T1 G  C0 exp{(t T0 )}S0dt  C0S0 /  C0S0 T 0 Eq.(2)

C0=C(T0) : Present concentration of d-TOC deposited T0 years ago S0 : Sedimentation rate (constant) α : Characteristic rate of the decomposition of d-TOC τ : Characteristic time of the decomposition of d-TOC Analyzed Parameters of Sediment Cores

WC : Water Content IL : Ignition Loss TOC : Total Organic Carbon TN : Total Nitrogen COD : Chemical Oxygen Demand AVS : Acid Volatile Sulfur Vertical Profiles of Sediment Parameters

A1 A2 A3

A6 A4 A5 A6 C/N Ratio

A4 A5 A6 COD/TOC Ratio

A4 A6 A5 Dissolved Oxygen Concentration above the Seafloor Observation data in 1986

Observation data in 2015

June July August September Features of Numerical Models Hydrodynamic Model 1. Three-dimensional, Time Dependent, Hydro-Static Model 2. Sea Surface Conformed Grid System 3. Quickest Scheme for Advection 4. Time Splitting Integration for External and Internal Modes 5. One Equation Turbulent Model (M & Y Level 2.0 + Galperin’s Modification) Pelagic Ecosystem Model 1. (ERSEM Like) Low Trophic Model 2. Coupled with Sedimentary Model

Sedimentary Model 1. One-dimensional Early Diagenesis Model 2. Ideas of H.Fossing (2004) and P.Berg (2003) are largely borrowed for setting-up. Computational Grids

Auxiliary Grids Main Grids

Arrangement of Grids in Vertical Section Arrangement of Horizontal Grids

Number of grid points: 107×103×41(vertical direction) Block Arrangement of Pelagic Ecosystem and Sediment model

Horizontal Grids & Blocks Vertical Arrangement

Number of grid points of Pelagic System: 107×103×41 or 21 (vertical direction) Nutrient Loading From Watershed (Pattern 1)

Ratio to the Load at 2010

1.0 T-N and T-P Concentration in the Surface Water

Case 2

N9 Vertical Contour of Water Temperature and Salinity at the Bay Head Station Water Temperature sea surface

Year 2012 Observation (MLIT data)

Year 2012 Water Depth Water Simulation

Salinity sea surface

Year 2012 Observation (MLIT data)

Year 2012 Water Depth Water Simulation

MLIT: Ministry of Land, Infrastructure and Transportation of Japan Vertical Contour of Dissolved Oxygen From 1986 to 2015

At Bay head Station

At Bay Center (St.11) Vertical Contour of Dissolved Oxygen at the Bay Head Station

Year 2010 Observation (MLIT data)

Year 2010 Water Depth Water Simulation (Case 2)

Year 2011 Observation (MLIT data)

Year 2011

Water Depth Water Simulation (Case 2)

Year 2012

Observation (MLIT data)

Year 2012 Water Depth Water Simulation (Case 2) Yearly Change of Hypoxic Water Volume

Observation Data surveyed by Mie prefecture

Simulation (Case 2) Vertical Profile of TOC Concentration in the Sediment Case 1

A1 A2 A3

A4 A5 A6 Vertical Profile of TOC Concentration in the Sediment Case 1

A1 A2 A3

A4 A5 A6 Dissolved Oxygen Concentration above Seafloor Year 2010 Aug.4 Sep.6 Oct.21

L L

Transient Solution (mg / l) Aug.4 Sep.6 Oct.21

Steady State Solution Phosphorus Budget in Primary Production Year Average of 2010 Unit: tonP/day Total of Entire Bay

3.7 6.6 31.6 River PO4 PO4 9.9 2.6 0.73 PhytoPl. 7.6 POP 2.94 POP 3.6 0.63 9.3 DOP PO4 Up. DOP 55.1 7.6 8.1 7.8 PO4 Sediment PO4 18.8 9.4 1.3 0.99 32.1 POP DOP ZooPl. 4.7 DOP 0.5 9.11 0.8 Ocean PO4 Ocean 0.8 0.7 0.12 POP 4.66 4.0 -0.4 0.11 Ocean DOP T-N Uptake Rate in Primary Production

571 558

417 396 325 298 T-P Uptake Rate in Primary Production

79.6 74.3

55.1 52.0 43.6 40.0 Summary

1. The field survey and consecutive analysis for the marine sediment in Ise Bay were conducted and it disclosed the distribution of the quantity as well as the age and the decomposition rate of the refractory organic matter(ROM). 2. The computer simulation with the sediment parameters obtained by the field survey was performed to investigate the response characteristics of the system of the bay. The effect of the excess accumulation of the ROM on the generation of the hypoxic water was quantified for the first time by the present work.