1. Ocean-scale modelling of Calanus finmarchicus
Douglas Speirs
Acknowledgments: Bill Gurney (Strathclyde)
Mike Heath (FRS Aberdeen)
Simon Wood (Glasgow University)
SOC, PML, SAHFOS, US-GLOBEC

2. Calanus finmarchicus – a marine copepod
Up to 90% of copepod biomass throughout the sub-arctic North Atlantic.
Important prey species for fish in both shelf and ocean ecosystems.
Extensive database from field surveys and laboratory experiments.
2 mm

3. The life-cycle of Calanus finmarchicus
Omnivorous, but feeds mainly on phytoplankton.
x1000 difference in body weight between eggs and adults.
Stage duration strongly dependent on temperature
Naupliar survival strongly dependent on food.
Reproduction & growth in upper layers (<200m).
Overwinters in a resting state at depths of m.

4. Coupling Life-Cycle to Physical Oceanography

5. Calanus abundance and Circulation

6. The modelling challenge
The Challenge
Physiologically and spatially explicit demographic model
Ocean-basin scale – advection plus diffusion
Hypothesis tests require wide parameter exploration
Need exceptional computational efficiency
The Solution
Focus on Calanus (physical and biotic environment as given)
Separate computation of physical and biological components
Discrete-time approach ( 104 speed-up relative to Lagrangian ensemble)

7. A Calanus-focussed model

8. The Biological Model
Development rate a function of temperature and food
Diapause entry from end C5
Fixed fraction of each generation enter diapause
Diapause exit photoperiod cued
Surface mortality increases with biomass and temperature

9. Yearly Population Cycle

10. Continuous Plankton Recorder Surveys

11. Test Data – Time Series & CPR

12. Water column integrated abundance of overwintering C4 and C5 C
Water column integrated abundance of overwintering C4 and C5 C. finmarchicus C5

13. Time Series Test
Gulf of Maine
OWS Mike
surface
C5-C6
diapause C5

14. Diapauser Survey Test

15. CPR Test
observed
predicted
Jan./Feb.
May/Jun.
Jul./Aug.

16. August Sea Temperature at 20m

17. The Impact of Transport

18. Domain Connectivity
Year 1
Year 3
Year 6

19. Travels of the Great Salinity Anomaly

20. Conclusions Fractional diapause entry Diapause entry late in C5
Photoperiod-cued diapause exit
Temperature-dependent mortality
Limited impact of transport
High domain connectivity
Ocean-scale population model feasible
Numerical efficiency is key

21. Washout of a non-developing population from Gulf of Maine

22. Boundary effects on C5-C6 seasonal cycle

23. Gulf of Maine Export

24. Invasion of Gulf of Maine

25. Future Prospects Tests on independent data sets
(UK-GLOBEC Irminger Sea data)
Automated parameter optimization
Hindcasting of decadal trends
Nested models for shelf regions
Coupled target species - ecosystem models

26. 1958-1999 average surface abundance of C
average surface abundance of C. finmarchicus (stage C5 and CVI)
1996-onwards
Calanus abundance map compiled from data supplied by SAHFOS to
NERCMarine Productivity project GR2/2749 and the EU-TASC project

27. Annual Mean Temperature & Food

28. Overwintering depths in various regions...C5

29. Geographical focus of Marine Productivity and other Calanus-centric programmes during the 1990’s..
Multi-national
programmes:
EU-ICOS
EU-TASC
National programmes:
UK, Norway, Germany, Denmark, Iceland, Canada, USA
NERC Marine
Productivity
Calanus abundance map compiled from data supplied by SAHFOS to
NERCMarine Productivity project GR2/2749 and the EU-TASC project

30. C5’s & phytoplankton carbon at OWSM
Diapause occurs at end of C5 stage
Fixed fraction of each generation