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

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

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 500-2000m.

Coupling Life-Cycle to Physical Oceanography

Calanus abundance and Circulation

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)

A Calanus-focussed model

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

Yearly Population Cycle

Continuous Plankton Recorder Surveys

Test Data – Time Series & CPR

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

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

Diapauser Survey Test

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

August Sea Temperature at 20m

The Impact of Transport

Domain Connectivity Year 1 Year 3 Year 6

Travels of the Great Salinity Anomaly

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

Washout of a non-developing population from Gulf of Maine

Boundary effects on C5-C6 seasonal cycle

Gulf of Maine Export

Invasion of Gulf of Maine

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

1958-1999 average surface abundance of C 1958-1999 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

Annual Mean Temperature & Food

Overwintering depths in various regions... C5

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

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