1. Eutrophication indicators PSA & EUTRISK
The eutrophication concept for coastal shallow waters
PSA
= Physically Sensitive
Areas to eutrophication
3D hydro-dynamical modelling
Bottom layer physics
High nutrient concentration
High phytoplankton biomass
Surface layer physics
Pressure
Effect
Impact
Supporting factors
Oxygen deficiency
EUTRISK
= Eutrophication Risk index
Remote sensing of Ocean Colour
In black = the eutrophication concept
In red = the inputs
In blue = the outputs = indicators
Jean-Noël DRUON

2. Eutrophication indicators PSA & EUTRISK
Monthly mean of the selected physical variables for areas <100m
Surface advection
Stratification
Monthly mean (solid) and standard deviation (dashed) of the selected physical variables for the Adriatic Sea (left) and the North Sea (right) for waters shallower than 100 m: a) mean advection of the mixed layer or residual current in case of tides (m s-1), b) maximum of the vertical density gradient estimated from mean daily profiles (kg m-4), and c) mean diffusivity coefficient near the sea floor (m2 s-1).
Bottom Friction
Adriatic Sea
North Sea

3. Eutrophication indicators PSA & EUTRISK
The stratification index,C_strat
Adriatic Sea
North Sea
Comparison of the stratification index, C_strat, in a) the Adriatic Sea and b) the North Sea (right) from January to December.

4. Eutrophication indicators PSA & EUTRISK
The advection and bottom friction indices, C_adv and C_kz_b (August)
Adriatic Sea
North Sea
Bottom Friction
Advection
Comparison of the spatial distribution of a) the advection index, C_adv, and b) the bottom diffusity index, C_kz_b, in the Adriatic Sea (left) and North Sea (right) for August.

5. Eutrophication indicators PSA & EUTRISK
The conceptual model
Surface Physics
= Potential primary production
(C_adv + C_strat)/2
(C_kz_b + 0.5*C_oxy_sat)/1.5
Dominant factors
PSA
Bottom diffusivity
High 
Low
= Oxygen availability
Bottom Physics No 
Stratification
Yes 
(C_kz_b + C_oxy_sat + C_strat + C_adv)/4
(C_kz_b + C_oxy_sat + C_strat + C_blt)/4
EUTRISK
Following the principle of the dominant factor, three formulations of the bottom physics index are used () ; the numbers allocated to each index indicate their use in C_phys_bott. C_kz_b is the bottom diffusivity index, C_oxy_sat is the oxygen saturation index, C_strat is the stratification index, C_adv is the advection index and C_blt is the benthic layer thickness index.
Surface phytoplankton biomass
Advection
= Oxygen consumption
Organic matter

6. Eutrophication indicators PSA & EUTRISK
April
August
Adriatic Sea
North Sea
The oxygen saturation index,C_oxy_sat
Comparison of the spatial distribution of the oxygen saturation index, C_oxy_sat, in the Adriatic Sea (left) and North Sea (right) for April and August computed from near bottom monthly means of temperature and salinity. Depths beyond 100 m are not calculated. South-West of Italy, West Channel and West of UK are not areas covered by the models.

7. Eutrophication indicators PSA & EUTRISK
The benthic layer thickness index,C_blt
August
Adriatic Sea
North Sea
TOP: Variation of the benthic layer thickness index function of the depth difference between the sea bottom and the pycnocline (C_blt  1).
BOTTOM: Comparison of the spatial distribution of the benthic layer thickness index, C_blt, in the Adriatic Sea (left) and North Sea (right) for August. Depths beyond 100 m are not calculated. South-West of Italy, West Channel and West of UK are not areas covered by the models.

8. Eutrophication indicators PSA & EUTRISK
High
Medium
Low
Sensitivity
April
August
December
Adriatic Sea North Sea
The bottom physics index,
C_Phys_bott
Or, where is the physical critical availability of oxygen near the bottom (supposing a uniform input of organic matter).
Comparison of the bottom physics index, C_Phys_bott, in a) the Adriatic Sea and b) the North Sea (right) in April, August and December. This index represents the physical availability of oxygen near the sea bottom (low towards red).

9. Eutrophication indicators PSA & EUTRISK
High
Medium
Low
Sensitivity
April
August
December
Adriatic Sea North Sea
The surface physics index,
C_Phys_surf
Or, where are the favourable physical conditions for the phytoplankton growth (supposing a uniform nutrient distribution).
Comparison of the surface physics index, C_Phys_surf, in a) the Adriatic Sea and b) the North Sea (right) in April, August and December. This index represents the favourable physical conditions for the phytoplankton growth (towards red).

10. Eutrophication indicators
Physically
Sensitive Areas
to eutrophication
PSA
High
Medium
Low
Sensitivity
Adriatic Sea North Sea
April
August
December
Or, where would be the bottom oxygen deficiencies with a uniform nutrient distribution and primary production.
The Physically Sensitive Area index to Eutrophication (PSA), based on 3D hydrodynamic modelling data (mainly advection, stratification and bottom friction), reveals how different is the physical resistance of coastal European regions to the eutrophication phenomena due to the diverse physical conditions.
Note the spatial and temporal variability. In black are the areas not covered by the model or water deeper than 100 m.

11. Eutrophication indicators PSA & EUTRISK
The conceptual model
PSA No 
High 
Surface Physics
Bottom Physics
= Oxygen availability
(C_kz_b + 0.5*C_oxy_sat)/1.5
Bottom diffusivity
Stratification
Low
Yes 
Dominant factors
= Potential primary production
(C_kz_b + C_oxy_sat + C_strat + C_adv)/4
(C_kz_b + C_oxy_sat + C_strat + C_blt)/4
(C_adv + C_strat)/2
EUTRISK
Surface phytoplankton biomass
Advection
= Oxygen consumption
Organic matter
Following the principle of the dominant factor, three formulations of the bottom physics index are used () ; the numbers allocated to each index indicate their use in C_phys_bott. C_kz_b is the bottom diffusivity index, C_oxy_sat is the oxygen saturation index, C_strat is the stratification index, C_adv is the advection index and C_blt is the benthic layer thickness index.

12. Eutrophication indicators
1- SeaWiFS Chl-a June 2000
2- Export of Chl-a with the monthly-mean advection
Vs=4m/d
The export of the organic matter
3- Sum while re-sampling on the model grid
Chl a
(mg m -3 )
Adriatic Sea

13. Eutrophication indicators
Adriatic Sea North Sea
The export of
the organic matter
0.65 * Log10 (Chl-a * deg + 1)

14. Eutrophication indicators
North Sea
Adriatic Sea
Eutrophication
Risk index
EUTRISK
Where are the most probable bottom oxygen deficiencies in
August 2000
Lowest monthly dissolved oxygen concentration
- 0 mg/l
- 2 mg/l
- 7 mg/l
- 5 mg/l
Eutrophic
Hypertrophic
Mesotrophic
Oligotrophic
Ecosystem status
The Eutrophication Risk index (EUTRISK) represents the most probable oxygen deficiency distribution near the bottom integrating physical modelling and satellite remote sensing estimate of chlorophyll-a, the latter being considered as the main source of organic matter. The EUTRISK separates strongly eutrophicated ecosystems (anoxia events) from resisting eutrophicated ecosystems (biological stress by oxygen hypoxia), and from meso- and ologotrophic ecosystems.

15. Eutrophication indicator EUTRISK -Validation
Dissolved Oxygen (mg/l) at the Bottom
July-August 1994 (Souvermezoglou and Krasakopoulou, 1999)
and EUTRISK
in August 1999
Northern Adriatic Sea 2 5 4 3
3.5
4.5
- 0 mg/l
- 2 mg/l
- 7 mg/l
- 5 mg/l
Lowest monthly dissolved oxygen concentrations
Note that the in situ measurements were done in 1994 and the EUTRISK is for 1999.

16. Eutrophication indicator EUTRISK -Validation
August 8th
August 13-14th
August 18th
August 24th
August 4th
Monitoring stations (pink dots and lines) August 1998 (ARPA)
Bottom oxygen (white lines):
hypoxia <2 mg/l (dashed)
anoxia (solid)
EUTRISK - August 1998
- 0 mg/l
- 2 mg/l
- 7 mg/l
- 5 mg/l
Lowest monthly dissolved oxygen concentrations
Note that the in situ measurements were done in 1994 and the EUTRISK is for 1999.

17. Eutrophication indicator EUTRISK - Validation
Minimum of bottom oxygen measurement (NERI )
and (1-EUTRISK)*10
August 2000 & September 1999
>4 mg/l
2-4 mg/l
0-2 mg/l
Danish Waters
The agreement is generally good, therefore underestimations can be found in areas where the model resolution (20 km) is too low to reproduce the physics at local scale (like in enclosed bays or straits).

18. Eutrophication indicators PSA & EUTRISK
Limitations
No cover for waters:
of the first nautical mile
extremely shallow (Z90=1/Kd)
deep (>100 m)
- surface chl-a concentrations ~ primary production
(C/Chl-a ratio, Irradiance, mixed layer depth)
temporal resolution
poor model resolution
degradation of the remote sensing resolution
index approach

19. Eutrophication indicators PSA & EUTRISK
Further improvements and extensions
- Improvement of the model resolution (from 20 km to 4-8 km),
Interpolation of the physical variables to the SeaWiFS grid at 2 km,
- Input of daily SST data at 2 km,
Extension of the methodology to all European coastal seas,
- Introduction of a more complete set of physical parameters,
- Modelling of the nitrogen and oxygen cycles.
u,v bottom layer + w + Irr0