Obey the LAW Calanus finmarchicus dormancy explained Jeffrey

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: Adults Dormancy at CV stage Emergence when… 1. Adult (CVI) proportion >= 0. 1 2. Back-calculation from early copepodid appearance, using development time-temperature relationship Copepodids Nauplii

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. Durb. In, M. Casas) PULSE – NEC: 2003 – 2005 (R. Jones)

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

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

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

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

Mean chlorophyll-a, 0 – 50 m Chl-a values truncated at 1. 6 mg m-3 (threshold for growth) Chl-a (mg m-3) Newfoundland Anticosti Gyre Rimouski Onset Emergence Scotian Shelf

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. 2001. Growth and development rates of the copepod Calanus finmarchicus reared in the laboratory. Mar. Ecol. Prog. Ser. 221: 161 -183

Miller et al. 1977. Growth rules in the marine copepod genus Acartia. L&O. 22: 326 -335.

Lipid Accumulation Window hypothesis: Step 1 - Conditions allowing dormancy: suppose only copepods with > 50% lipid content can enter 0. 5 0. 4 Integrated 0. 3 Food 0. 2 0. 1 0. 0 Integrated Temperature Fraction lipid content at end of CV stage

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

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

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

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

Testing the hypothesis Temperature (°C) … Time Potential lipid accumulation Chlorophyll (mg m-3) 1. Identify lipid accumulation windows by starting individual-based model runs, driven by temperature and chlorophyll, at each date Threshold for onset of dormancy Time 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 NH 20, 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 125 -175 in the S, and between days 175 -225 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 predict Calanus population responses to climate changes