Obey the LAW: Calanus finmarchicus dormancy explained Jeffrey Runge School of Marine Sciences, University of Maine and Gulf of Maine Research Institute Andrew Leising NOAA, Southwest Fisheries Science Center Catherine Johnson University of British Columbia

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 individual-based models, develop quantitative hypotheses to explain patterns

Proxies for dormancy entry and exit Entry: Fifth copepodid (CV) half-max proxy Dormant when… CV proportion >= x-bar /2 where x-bar = average max. CV proportion over all years 1.Exit: Emergence when… 1. Adult (CVI) proportion >= Back-calculation from early copepodid appearance, using development time-temperature relationship Copepodids Nauplii Adults Dormancy at CV stage

Data sources 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)

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

Photoperiod at emergence and onset Rimouski Anticosti Gyre Newfoundland Scotian Shelf Daylength (h) Day of Year Emergence date Previous and next date

Temperature at 5 m Temperature (°C) Rimouski Anticosti Gyre Newfoundland Scotian Shelf Onset Emergence

Climatological temperature at 5 m Onset Emergence Rimouski Anticosti Gyre Newfoundland Scotian Shelf Temperature (°C)

Mean chlorophyll-a, 0 – 50 m Chl-a (mg m -3 ) Rimouski Anticosti Gyre Newfoundland Scotian Shelf Chl-a values truncated at 1.6 mg m -3 (threshold for growth) Onset Emergence

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

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 propose a “Lipid- Accumulation Window” hypothesis to explain observed life history patterns.

Growth of Neocalanus plumchrus copepodids in the southeastern Bering Sea

Development time is a function of temperature and food concentration in Calanus finmarchicus Campbell, R. M. Wagner, G. Teegarden, C. Boudreau and E. Durbin Growth and development rates of the copepod Calanus finmarchicus reared in the laboratory. Mar. Ecol. Prog. Ser. 221:

Miller et al Growth rules in the marine copepod genus Acartia. L&O. 22:

Lipid Accumulation Window hypothesis: Step 1 - Conditions allowing dormancy: suppose only copepods with > 50% lipid content can enter Integrated Temperature Integrated Food Fraction lipid content at end of CV stage

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

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

Lipid accumulation window hypothesis: Step 3 - Predation Filter Time Favorable Env. Conditions Predation Removal here Resulting population entering dormancy Missing cohort here

Lipid accumulation window hypothesis: Step 4 - Emergence Timing linked to Entry Emergence survival linked to entry and Env. Time Favorable Env. Conditions Jan Population entering dormancy Population exiting dormancy Successful females Dormancy Length, f(T during dormancy,% lipids at entry)

Testing the hypothesis 1.Identify lipid accumulation windows by starting individual-based model runs, driven by temperature and chlorophyll, at each date Time  Chlorophyll (mg m -3 ) Temperature (°C) … Potential lipid accumulation Time  Threshold for onset of dormancy 2. CVs produced during the lipid accumulation window can enter dormancy

Utility of the model for this calculation Growth and development are decoupled Ability to include temporally variable forcing data (food and temperature) Can include or ignore predation filter Mechanistic and physiological basis for growth and development

Example Results for C. pacificus Top figure is based on climatology from NH20, Newport Line, OR; Bottom figure based on SCB climatology In the south, copepods spawned as early as day 50 can enter dormancy, whereas in the north, it’s 40 days later. Peak dormancy entrance date is between days in the S, and between days in N. Predation during the “Green” period would remove potentially successful copepods Suboptimal cold temperatures(and low food) in the N during the early part of the year limit success then, whereas overly warm temperatures later in the year limit success in S during that time (recall the optimal window)

Final Conclusions Our findings for C. finmarchicus, C. pacificus and C. marshallae strongly suggest that multiple environmental factors are the likely cues for dormancy, as these copepods enter and exit dormancy over a wide range of times and conditions. Our modeling results (for C. pacificus so far) suggest that lipid accumulation (or some equivalent storage compound) is a likely player in how dormancy is triggered. OBEY THE LAW!!!!

Implications Previous coupled 3-d physical-biological models of Calanus have forced dormancy transitions empirically using an advective-diffusive approach While these models provide diagnostic insight, they cannot be used for prediction A mechanistic, coupled IBM-physical model that tracks lipid accumulation is needed to understand and predict Calanus population responses to climate changes

Final Conclusions Our findings for C. finmarchicus, C. pacificus and C. marshallae strongly suggest that multiple environmental factors are the likely cues for dormancy, as these copepods enter and exit dormancy over a wide range of times and conditions. Our modeling results (for C. pacificus so far) suggest that lipid accumulation (or some equivalent storage compound) is a likely player in how dormancy is triggered.

Lipid accumulation window hypothesis: Step 1 - Conditions allowing dormancy Calanus pacificus, simulated growth under constant conditions

Lipid accumulation window hypothesis: Step 1 - Suppose only copepods with > 50% lipid can enter

Lipid accumulation window hypothesis: Step 1 - These “fat” copepods are also the larger copepods Optimal Food/Temperature Window