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ECCWO Symposium - Session 12: Scenarios and models to explore the future of marine coupled human-natural systems under climate change

EcoTroph, a quasi-physical ecosystem model

to analyze the global impact of climate change on marine food-webs

Didier GASCUEL, Hubert DU PONTAVICE, William W. L. CHEUNG

http://web.nkc.kku.ac.th/118428/images/Pk/cyclop.%20calanus.gif

http://ic.ucsc.edu/%7Ewxcheng/envs161/Lecture8/Flagellate.jpg

http://www.kerkena.com/images/Pieuvre.gif

http://www.ifremer.fr/drvpbessin/images/seiche5.jpg

http://www.chartingnature.com/img/AF/RedHake.jpg

EcoTroph: an over-simplified ecosystem model

ECCWO 2018, S12-1420, EcoTroph Agrocampus Ouest, D. Gascuel - 2 / 17

Grd.zoo.

Crustac.

Dem.in

Ethmal.

Céphal. Bathy.

Mulets

Capit.

Dem.p.

Bars

Grd.pél. Req.rai

Daup.

Bal

Artisanal fishery

Indust. fishery

1

2

3

4

TL

Petit Zooplanc.

Producteurs primaires

Détritus

Ptt.pél.

Benthos

.01

0.1

1.0

10.0

100.0

2,0 2,5 3,0 3,5 4,0 4,5 5,0 Trophic level

Total ecosystem Biomass (tons/km2)






EcoTroph: applications

Climate change as the driver ?

Over exploited

Fully exploited

to draw diagnostics (Meissa et al., 2015)

0,01

0,10

1,00

10,00

100,00

2,0 2,5 3,0 3,5 4,0 4,5 5,0

Biomass spectrum

Increasing mEIncreasing F

to assess fishing impacts (Gascuel et al., 2005)

0.010.1

110

100

2 3 4 5

+6%

+24%

+17%

0.010.1

110

100

2 3 4 5

+36%

-8%

Biomass (log t/km²)

1980 2013

TL

Envir. Manag.

Bay of Biscay Celtic Sea

to compare ecosystem’s structure and dynamics (Moullec et al., 2016)

to explore functioning (Bentorcha et al., 2016)

0

5

10

15

20

2,0 2,5 3,0 3,5 4,0

Niveau trophic

Abo

ndan

ce (T

/km

2)

2003 (Exploited)

2008 (MPA)

Simulated MPA

to monitor MPA’s benefits (Colleter et al., 2012)

0,01

0,10

1,00

10,00

100,00

2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5Niveau trophique

EcopathOsmose

Biomasses de l'écosystème

to compare models (Gasche et al., 2012)


Effo

rt m

ultip

lier I

PF

Biomass TL-Biomass

Catch TL-Catch

Effo

rt m

ultip

lier I

PF

Effort multiplier SSCF Effort multiplier SSCF

to quantify interactions (Gasche et al., 2013)

2000s

to map global fisheries impacts (Tremblay-Boyer et al., 2011)






0,0

0,2

0,4

0,6

0,8

1,0

1,2

1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 Trophic level τ

Biomass

1,0

Grazing

Primary production Detritus recycling

EcoTroph: how it works?

A continuous representation of the biomass distribution, according to trophic level τ

-> the Biomass Trophic spectrum

Biomass flow

Predation

Ontogeny The ecosystem functioning: a flow of biomass trough trophic levels

Gascuel, 2005 … Gascuel, Pauly, 2009 … Gascuel, Guénette, Pauly, 2011







EcoTroph: two key parameters

4,0 + 1,0 2,0 2,5 3,0 3,5 Trophic level

Transfer efficiency

The transfer efficiency TE: defines the quantity of biomass flow (Φτ), at each trophic level

Speed of the biomass flow

The flow kinetics K: celerity of biomass transfers through the food web (in TL/y-1)

NB: 1/K is the residence time in the food web







EcoTroph: basic equations

The master equation: Biomass = flow . ∆τ

speed


Bτ = Φτ · ∆τ / Kτ

An explicit link between:

the biomass present in the trophic class [τ, τ+∆τ[ -> Bτ, in tonnes the production, which results from the biomass flow passing trough the trophic

class -> Pτ = Φτ · ∆τ, in tonnes/year








A non-conservative flow: Φτ + ∆τ = Φτ · e – ( µτ + ϕτ ) . ∆τ

speed

Fishing losses . Catches Y

Natural losses . Non pred.mort. Mo.B . Excretion U . Respiration R

e-µ =Transfer efficiency



Φ Q

Y=F.B Mo.B

M2.B Φ

U R

Growth Prey Predator







speed



A non-conservative flow: Φτ + ∆τ = Φτ · e – ( µτ + ϕτ ) . ∆τ

An empirical model for kinetics: Kτ,unexpl. = a · τ -b


Gascuel et al. (2008, Ecol.Mod) 55 Ecopath models n = 1,718 groups r2 = 0.54

= 20.2 · e 0.041 θ · τ -3.26






EcoTroph: additional details

0,01

0,10

1,00

10,00

100,00

2,0 2,5 3,0 3,5 4,0 4,5 5,0 Trophic level

total Biomass accessible Biomass

Fishing impact on kinetic (higher mortalities -> shorter life expectancy -> faster transfers)

Feedback effects: Of predators on prey (Top-down control: more predator -> faster transfers) Of the total biomass on detritus recycling (less biomass -> less recycling)

All organisms are (currently) not exploited The accessible biomass A distinct kinetics for the accessible

and the not-accessible biomass


Top predators








A non-conservative flow: Φτ + ∆τ = Φτ · e – ( µτ + ϕτ ) . ∆τ Φ1 = NPP

An empirical model for kinetics: Kτ,unexpl. = a · τ -b = 20.2 · e 0.041 θ · τ -3.26

speed Bτ = Φτ · ∆τ / Kτ

Climate change affects: Net Primary Production NPP

Transfer efficiency TE

Flow kinetics K







Using EcoTroph to simulate climate change

A global analysis Using 1° cells, aggregated by ecosystem type And for 2 scenarios: RCP2.6 and RCP8.5 in 2100 From IPSL

From Du Pontavice (in prep., See S11-1540)

Transfer efficiency TE

SST







Using EcoTroph to simulate climate change

A global analysis Using 1° cells, aggregated by ecosystem type And for 2 scenarios: RCP2.6 and RCP8.5 in 2100 From IPSL

From Du Pontavice (in prep., See S11-1540)

From Gascuel et al. (2008) 1

2

3

4

5

0 1 2 3 4 5 6 7Time (year)

Trop

hic

leve

l TL

29 °C25 °C20 °C15 °C10 °C5 °C0 °C







Climate change effects on the biomass trophic spectra

Temperate ecosystems, RCP 8.5, biomass in tons/km2

No change in NPP

A large effect of changes in Transfer efficiency TE

An additional effect of change in kinetics K

A 29% decrease in the total consumer biomass


NPP only






Effects on Production, Biomass & Accessible biomass

Polar Temperate Tropical

Production (tons/y/km2)

Biomass (tons/km2)

Accessible Biomass (tons/km2)







Effects on Production, Biomass & access.Biomass

Loss in total consumer Production 2010

Base line 2100

RCP 2.6 2100

RCP 8.5 Polar 0% 3% 14% Temperate 0% 3% 16% Tropical 0% -1% 12%

2100 RCP 8.5 TE only NPP only K only

10% 4% 0% 15% 1% 0%

1% 11% 0%

12% 4% 7% 18% 1% 12%

2% 11% 14%

Access. Biomass

Top-pred. Biomass

26% 31% 35% 44% 25% 26%

A large impact on production and biomass, especially in temperate ecosystems Key role of NPP in tropical ecosystems, TE in temperate and polar, K everywhere Highest impacts on accessible and top-predator’s biomass


Loss in total consumer Biomass

Polar 0% 5% 22% Temperate 0% 6% 29% Tropical 0% 2% 25%






Global effects

RCP 2.6 -1 % -5 %

RCP 8.5 -14 % -25 % Accessible Biomass -28 % Top-predator biomass -33 %







Discussion & Conclusion


Next steps: Include catches Run the model locally (1° cells) Sensitivity analyses (beyond IPSL) Add changes (in TE and K) occurring

at the individual level

Take-home messages Simple model may provide reliable results (TrophMod, as an integrative tool)

Climate change will affect food web functioning, through three mechanisms: changing NPP, decreasing Transfer efficiencies, and accelerating the flow kinetics…

… thus leading to a large decrease in total consumer production, biomass and structure

Du Pontavice et al., in prep.






Thank you…

ECCWO 2018, S12-1420, EcoTroph Agrocampus Ouest, D. Gascuel

1

2

3

4

5

0 1 2 3 4 5 6 7Time (year)

Trop

hic le

vel T

L

29 °C25 °C20 °C15 °C10 °C5 °C0 °C






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