Development of the Lipid Accumulation Window hypothesis to explain Calanus finmarchicus dormancy

1. Development of the Lipid Accumulation Window hypothesis to explain Calanus finmarchicus dormancy Jeffrey RungeSchool of Marine Sciences, University of Maine and Gulf of Maine Research Institute Andrew LeisingNOAA, Southwest Fisheries Science Center Catherine JohnsonUniversity of British Columbia

2. Objectives: • Identify environmental processes that control dormancy in Calanus finmarchicus • Develop a mechanistic understanding of dormancy for inclusion in population dynamics modeling • Approach: • Compile Calanus and environmental data across regions in the NW Atlantic • Look for common patterns and cues • Using an individual-based model, develop quantitative hypotheses to explain patterns

3. Data Sources and Collaborators Data from: DFO – AZMP: 1999 – 2005 (E.Head, P.Pepin) DFO – IML:1990 – 1991 (S. Plourde, P. Joly) US-GLOBEC: 1995 – 1999 (E. DurbIn, M. Casas) PULSE – NEC: 2003 – 2005 (R. Jones)

4. Proxies for dormancy entry and exit Dormancy Entry (Onset)Fifth copepodid (CV) half-max proxy Dormant when… CV proportion ≥x / 2 where x = average max. CV proportion over all years Exit (Emergence)Emergence when… 1. Adult (CVI) proportion ≥ 0.1 2. Back-calculation from early copepodid appearance, using development time-temperature relationship

5. Abundance (no. m-2) Stage Proportion AG: Anticosti Gyre, NW Gulf of St. Lawrence OnsetEmergence

6. Possible dormancy cues Emergence Photoperiod(Miller et al., 1991; Speirs et al., 2004) Disturbance(Miller & Grigg, 1991) Development(Hind et al., 2000) Onset Photoperiod(Miller et al., 1991) Temperature(Niehoff & Hirche, 2005) Food availability(Hind et al., 2000) Lipid accumulation (hormonal link?)(Irigoien, 2004)

7. Climatological temperature at 5 m Newfoundland Anticosti Gyre Temperature (°C) Rimouski Onset Emergence Scotian Shelf Day of Year

8. Mean chlorophyll-a, 0 – 50 m Newfoundland Anticosti Gyre Chl-a (mg m-3) Rimouski Onset Emergence Scotian Shelf --- half-saturation [Chl-a] Day of Year

9. Analysis of variance

10. Conclusions • No single observed environmental cue explains dormancy patterns • Dormancy entry and emergence occur over a broad range of times, both among individuals and years The mechanistic understanding of dormancy transitions must involve interaction of multiple environmental factors. We develop a “lipid-accumulation window” hypothesis to explain observed life history patterns.

11. Lipid accumulation window hypothesis: Individuals can only enter dormancy if their food and temperature history allows them to accumulate sufficient lipid • Development rate increases faster with temperature than growth rate • Lipid production integrates temporally variable food and temperature history • We hypothesize cue for entry occurs prior to stage CV. • Mortality also influences probability of reaching CV dormant stage Miller et al. 1977. Growth rules in the marine copepod genus Acartia. L&O. 22: 326-335.

13. Lipid accumulation window hypothesis:Step 1:Decision to enter dormancy in stage CV is made in stage CIV. Criterion is attainment of 30% lipid content by wt. Food index

14. Durbin et al. 2003: Gulf of Maine Runge et al. (2006.): Georges Bank Calanus finmarchicus: Relationship of egg production to phytoplankton biomass

15. Lipid accumulation window hypothesis:Step 2 - Temporal Filter Cumulative conditions that will allow dormancy in CIV and CV Favorable Env. Conditions Lipid Threshold Time

16. Lipid accumulation window hypothesis: Step 2 - Temporal Filter Cumulative conditions that will allow dormancy Resulting period when they go dormant Favorable Env. Conditions Time

17. Lipid accumulation window hypothesis: Step 3 - Emergence Timing linked to EntryEmergence survival linked to entry and Env. Population entering dormancy Population exiting dormancy Favorable Env. Conditions Successful females Jan Jan Time Dormancy Length, f(T during dormancy,% lipids at entry)

18. AG

19. Anticosti Gyre climatology

20. Anticosti Gyre Observed climatology Model simulation

22. Rimouski Observed climatology Model simulation

23. Next Steps • Work on parameters for model for C. finmarchicus; development of general set for all of NW Atlantic • Test LAW model against C. finmarchicus life cycle data sets in the NW Atlantic. Does the model reproduce variability in individual years? • Test refined and alternative hypotheses- Additional conditions required? • Examine mechanisms for emergence from dormancy: parameterization of Saumweber and Durbin functions for potential diapause duration • Examine influence of climate change scenarios on Calanus life cycle and population dynamics • Further testing with time series observations, include measures of lipid levels in CIV and CV