We used EwE-F, a Fortran version of Ecosim, to implement a two-way coupling between a food web model and a biogeochemical model of the Baltic Sea.

Two-way coupling between Ecosim (EwE-F) and a biogeochemical model of the Baltic Sea

Bärbel Muller-Karulis¹, Ekin Akoglu², Maciej T. Tomczak¹, Bo Gustafsson¹

1Stockholm University, Baltic Nest Institute, Baltic Sea Centre, SE-106 91, Stockholm, Sweden

2Middle East Technical University, Institute of Marine Sciences, P.O. Box 28, 33731, Erdemli, Turkey

Acknowledgement:

This work resulted from the BONUS Bluewebs project and the EU Horizon 2020 research and innovation project ClimeFish. BONUS Bluewebs has received funding from BONUS (Art 185), funded jointly by the EU and FORMAS. The Baltic Nest Institute is supported by the Swedish Agency for Marine and Water Management through their grant 1:11 - Measures for marine

and water environment.

BALTSEM

1-D EwE-F

0-D

Phyto profile

updates Phyto

dPhyto

dt HTL

distributes

to Phyto profile

dPhyto

dt dPhyto

dt HTL

dPhyto

dt biogeo

= +

dPhyto

dt

We used EwE-F, a Fortran version of Ecosim, to

implement a two-way coupling between a food

web model and a biogeochemical model of the

Baltic Sea.

Coupling strategy: shared components

Shared components: Phytoplankton, suspended and sediment detritus

Time-step: as in biogeochemical model (hours)

Implementation of nutrient fluxes

HTL component

Prey C, N, P

ingestion

Surplus

excretion Growth

B*P/Q

N, P surplus < 0

Reduce growth

HCO

, NH

,

PO

Coupling creates seasonality

Coupled model performance

fixed stoichiometry for all components, balanced C, N, and P fluxes

Coupled model feedbacks

0 20 40 60 80 100 120 140 160 180 200

Uncoupled Coupled

Consumption (g C m-2 y-1)

Zooplankton Other HTL

0 2 4 6 8 10 12 14

Uncoupled Coupled

Recycling (g N m-2 y-1)

Zooplankton Other HTL

Similar zooplankton biomass, but higher grazing and

nutrient regeneration in uncoupled BALTSEM -> higher primary production

Trophic cascades

Biomass dynamics of zooplankton and sprat, a

planktivorous fish, with parameters from original annual Ecosim model

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Plankt. Fish Zooplankton Phytoplankton

Biomass (g C m-2)

Low planktivorous fish High planktivorous fish

High planktivorous fish biomass creates low

zooplankton biomass, but has with current

vulnerabilities no effect on phytoplankton

Coupled model behaviour in scenario runs with high and low fishing pressure on planktivorous fish